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  • Acoustics
  • 2015-2019
  • 2010-2014  (89)
  • 1960-1964
  • 1945-1949
  • 2010  (89)
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  • 2015-2019
  • 2010-2014  (89)
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  • 1
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    Animal behaviour: How to confuse thirsty bats (2010)
    Nature Publishing Group (NPG)
    Details
    Publikationsdatum: 2010-11-12
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tonzani, Stefano -- England -- Nature. 2010 Nov 11;468(7321):181. doi: 10.1038/468181a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21068821" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Acoustics ; Animals ; Chiroptera/*physiology ; Drinking ; Echolocation/*physiology ; Metals ; Plastics ; Surface Properties ; Thirst ; Touch/physiology ; Vision, Ocular/physiology ; Water/*analysis ; Wood
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 2
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    Cabin Noise Studies for the Orion Spacecraft Crew Module (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Controlling cabin acoustic noise levels in the Crew Module (CM) of the Orion spacecraft is critical for adequate speech intelligibility, to avoid fatigue and to prevent any possibility of temporary and permanent hearing loss. A vibroacoustic model of the Orion CM cabin has been developed using Statistical Energy Analysis (SEA) to assess compliance with acoustic Constellation Human Systems Integration Requirements (HSIR) for the on-orbit mission phase. Cabin noise in the Orion CM needs to be analyzed at the vehicle-level to assess the cumulative acoustic effect of various Orion systems at the crewmember's ear. The SEA model includes all major structural and acoustic subsystems inside the CM including the Environmental Control and Life Support System (ECLSS), which is the primary noise contributor in the cabin during the on-orbit phase. The ECLSS noise sources used to excite the vehicle acoustic model were derived using a combination of established empirical predictions and fan development acoustic testing. Baseline noise predictions were compared against acoustic HSIR requirements. Key noise offenders and paths were identified and ranked using noise transfer path analysis. Parametric studies were conducted with various acoustic treatment packages in the cabin to reduce the noise levels and define vehicle-level mass impacts. An acoustic test mockup of the CM cabin has also been developed and noise treatment optimization tests were conducted to validate the results of the analyses.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-21896 , 17th AIAA/CEAS Aeroacoustics Conference; Jun 06, 2011 - Jun 08, 2011; Portland, OR; United States|32nd AIAA Aeroacoustics Conference; Jun 06, 2011 - Jun 08, 2011; Portland, OR; United States
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  • 3
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    Acoustic Measurements of Small Solid Rocket Motor (2010)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Rocket acoustic noise can induce loads and vibration on the vehicle as well as the surrounding structures. Models have been developed to predict these acoustic loads based on scaling existing solid rocket motor data. The NASA Marshall Space Flight Center acoustics team has measured several small solid rocket motors (thrust below 150,000 lbf) to anchor prediction models. This data will provide NASA the capability to predict the acoustic environments and consequent vibro-acoustic response of larger rockets (thrust above 1,000,000 lbf) such as those planned for the NASA Constellation program. This paper presents the methods used to measure acoustic data during the static firing of small solid rocket motors and the trends found in the data.
    Schlagwort(e): Acoustics
    Materialart: M10-0180 , 159th ASA Meeting and Norse-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
    Format: text
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  • 4
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    Condenser Microphone Protective Grid Correction for High Frequency Measurements (2010)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Use of a protective grid on small diameter microphones can prolong the lifetime of the unit, but the high frequency effects can complicate data interpretation. Analytical methods have been developed to correct for the grid effect at high frequencies. Specifically, the analysis pertains to quantifying the microphone protective grid response characteristics in the acoustic near field of a rocket plume noise source. A frequency response function computation using two microphones will be explained. Experimental and instrumentation setup details will be provided. The resulting frequency response function for a B&K 4944 condenser microphone protective grid will be presented, along with associated uncertainties
    Schlagwort(e): Acoustics
    Materialart: M10-0112 , Acoustical Socity of America Conference; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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  • 5
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    Relation Between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This paper reviews Lilley s reformulation of Lighthill s equation and shows that it can be obtained as a special case of a much more general acoustic analogy. It also shows how this generalized analogy can be used to eliminate some of the difficulties that arise when more conventional parallel flow analogies are applied to high speed jets. And, finally, some recent applications of these ideas are discussed.
    Schlagwort(e): Acoustics
    Materialart: E-17986 , International Journal of Aeroacoustics; 9; 4 ad 5; 401-418
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  • 6
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    An MDOE Investigation of Chevrons for Supersonic Jet Noise Reduction (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The impact of chevron design on the noise radiated from heated, overexpanded, supersonic jets is presented. The experiments used faceted bi-conic convergent-divergent nozzles with design Mach numbers equal to 1.51 and 1.65. The purpose of the facets was to simulate divergent seals on a military style nozzle. The nozzle throat diameter was equal to 4.5 inches. Modern Design of Experiment (MDOE) techniques were used to investigate the impact of chevron penetration, length, and width on the resulting acoustic radiation. All chevron configurations used 12 chevrons to match the number of facets in the nozzle. Most chevron designs resulted in increased broadband shock noise relative to the baseline nozzle. In the peak jet noise direction, the optimum chevron design reduced peak sound pressure levels by 4 dB relative to the baseline nozzle. The penetration was the parameter having the greatest impact on radiated noise at all observation angles. While increasing chevron penetration decreased acoustic radiation in the peak jet noise direction, broadband shock noise was adversely impacted. Decreasing chevron length increased noise at most observation angles. The impact of chevron width on radiated noise depended on frequency and observation angle.
    Schlagwort(e): Acoustics
    Materialart: AIAA-Paper-2010-3926 , E-17944 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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  • 7
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    Spacecraft Internal Acoustic Environment Modeling (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Acoustic modeling can be used to identify key noise sources, determine/analyze sub-allocated requirements, keep track of the accumulation of minor noise sources, and to predict vehicle noise levels at various stages in vehicle development, first with estimates of noise sources, later with experimental data. This paper describes the implementation of acoustic modeling for design purposes by incrementally increasing model fidelity and validating the accuracy of the model while predicting the noise of sources under various conditions. During FY 07, a simple-geometry Statistical Energy Analysis (SEA) model was developed and validated using a physical mockup and acoustic measurements. A process for modeling the effects of absorptive wall treatments and the resulting reverberation environment were developed. During FY 08, a model with more complex and representative geometry of the Orion Crew Module (CM) interior was built, and noise predictions based on input noise sources were made. A corresponding physical mockup was also built. Measurements were made inside this mockup, and comparisons were made with the model and showed excellent agreement. During FY 09, the fidelity of the mockup and corresponding model were increased incrementally by including a simple ventilation system. The airborne noise contribution of the fans was measured using a sound intensity technique, since the sound power levels were not known beforehand. This is opposed to earlier studies where Reference Sound Sources (RSS) with known sound power level were used. Comparisons of the modeling result with the measurements in the mockup showed excellent results. During FY 10, the fidelity of the mockup and the model were further increased by including an ECLSS (Environmental Control and Life Support System) wall, associated closeout panels, and the gap between ECLSS wall and mockup wall. The effect of sealing the gap and adding sound absorptive treatment to ECLSS wall were also modeled and validated.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-22307 , International Academy of Astronautics: Humans in Space Symposium; Apr 11, 2011 - Apr 15, 2011; Houston, TX; United States
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  • 8
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    Acoustic Noise Prediction of the Amine Swingbed ISS ExPRESS Rack Payload (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Acoustics plays a vital role in maintaining the health, safety, and comfort of crew members aboard the International Space Station (ISS). In order to maintain this livable and workable environment, acoustic requirements have been established to ensure that ISS hardware and payload developers account for the acoustic emissions of their equipment and develop acoustic mitigations as necessary. These requirements are verified by an acoustic emissions test of the integrated hardware. The Amine Swingbed ExPRESS (Expedite the PRocessing of ExperimentS to Space) rack payload creates a unique challenge to the developers in that the payload hardware is transported to the ISS in phases, making an acoustic emissions test on the integrated flight hardware impossible. In addition, the payload incorporates a high back pressure fan and a diaphragm vacuum pump, which are recognized as significant and complex noise sources. In order to accurately predict the acoustic emissions of the integrated payload, the individual acoustic noise sources and paths are first characterized. These characterizations are conducted though a series of acoustic emissions tests on the individual payload components. Secondly, the individual acoustic noise sources and paths are incorporated into a virtual model of the integrated hardware. The virtual model is constructed with the use of hybrid method utilizing the Finite Element Acoustic (FEA) and Statistical Energy Analysis (SEA) techniques, which predict the overall acoustic emissions. Finally, the acoustic model is validated though an acoustic characterization test performed on an acoustically similar mock-up of the flight unit. The results of the validated acoustic model are then used to assess the acoustic emissions of the flight unit and define further acoustic mitigation efforts.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-22103 , 41st International Conference on Environmental Systems; Jul 17, 2011 - Jul 21, 2011; Portland, OR; United States
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  • 9
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    Optimization of Noise Performance of Low-Back Ground Detector Arrays (2010)
    In:  Other Sources
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    Publikationsdatum: 2019-07-19
    Beschreibung: The performance of the 2k x 2k Teledyne H2RG detectors is key to the success of the JWST mission. For broadband imaging, where background limited sensitivity is quickly reached, the key parameter is the quantum efficiency of the detectors, which is, in general, very good. For near infrared spectroscopy and narrow band imaging, we cannot generally reach the back-round limit, so instrument sensitivity is directly dependent on the read noise of the detector. We have initiated a program to analyze the noise characteristics of the H2RG detectors, studying the correlations among the detector outputs and with the reference output, as well as the temporal correlations in a given detector section. Lasing the measured characteristics of the noise correlations, we can determine the optimal coefficients for the removal of correlated noise as a function of frequency. By using available reference sources and adding more frequent references, we have been able to reduce the noise by a factor of two. We find that the detectors have significantly lower noise that observed in prior tests, and can offer significant improvements in the performance of the JWST instruments. We will present the analysis and mitigation techniques, discuss prospects for further improvements with existing detectors, and describe considerations for improvements in next-generation detectors.
    Schlagwort(e): Acoustics
    Materialart: Observational Frontiers of Astronomy for the New Decade; Jun 26, 2010 - Jun 30, 2010; San Diego, CA; United States
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  • 10
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    An Acoustical Comparison of Sub-Scale and Full-Scale Far-Field Measurements for the Reusable Solid Rocket Motor (2010)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Recently, members of the Marshall Space Flight Center (MSFC) Fluid Dynamics Branch and Wyle Labs measured far-field acoustic data during a series of three Reusable Solid Rocket Motor (RSRM) horizontal static tests conducted in Promontory, Utah. The test motors included the Technical Evaluation Motor 13 (TEM-13), Flight Verification Motor 2 (FVM-2), and the Flight Simulation Motor 15 (FSM-15). Similar far-field data were collected during horizontal static tests of sub-scale solid rocket motors at MSFC. Far-field acoustical measurements were taken at multiple angles within a circular array centered about the nozzle exit plane, each positioned at a radial distance of 80 nozzle-exit-diameters from the nozzle. This type of measurement configuration is useful for calculating rocket noise characteristics such as those outlined in the NASA SP-8072 "Acoustic Loads Generated by the Propulsion System." Acoustical scaling comparisons are made between the test motors, with particular interest in the Overall Sound Power, Acoustic Efficiency, Non-dimensional Relative Sound Power Spectrum, and Directivity. Since most empirical data in the NASA SP-8072 methodology is derived from small rockets, this investigation provides an opportunity to check the data collapse between a sub-scale and full-scale rocket motor.
    Schlagwort(e): Acoustics
    Materialart: M10-0181 , 159th ASA Meeting and Noise-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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  • 11
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    Interference-free ultrasound imaging during HIFU therapy, using software tools (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: Disclosed herein is a method for obtaining a composite interference-free ultrasound image when non-imaging ultrasound waves would otherwise interfere with ultrasound imaging. A conventional ultrasound imaging system is used to collect frames of ultrasound image data in the presence of non-imaging ultrasound waves, such as high-intensity focused ultrasound (HIFU). The frames are directed to a processor that analyzes the frames to identify portions of the frame that are interference-free. Interference-free portions of a plurality of different ultrasound image frames are combined to generate a single composite interference-free ultrasound image that is displayed to a user. In this approach, a frequency of the non-imaging ultrasound waves is offset relative to a frequency of the ultrasound imaging waves, such that the interference introduced by the non-imaging ultrasound waves appears in a different portion of the frames.
    Schlagwort(e): Acoustics
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  • 12
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    Finite Element Models and Properties of a Stiffened Floor-Equipped Composite Cylinder (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Finite element models were developed of a floor-equipped, frame and stringer stiffened composite cylinder including a coarse finite element model of the structural components, a coarse finite element model of the acoustic cavities above and below the beam-supported plywood floor, and two dense models consisting of only the structural components. The report summarizes the geometry, the element properties, the material and mechanical properties, the beam cross-section characteristics, the beam element representations and the boundary conditions of the composite cylinder models. The expressions used to calculate the group speeds for the cylinder components are presented.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216192 , L-19814 , LF99-10078
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  • 13
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    Human Response to Low-Intensity Sonic Booms Heard Indoors and Outdoors (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: Test subjects seated inside and outside a house were exposed to low-intensity N-wave sonic booms during a 3-week test period in June 2006- The house was instrumented to measure the booms both inside and out. F-18 aircraft were flown to achieve a variety of boom overpressures from approximately .1 to .6 psf During four test days, seventy-seven test subjects heard the booms while seated inside and outside the house. Using the Magnitude Estimation methodology and artificial reference sounds ; the subjects rated the annoyance of the booms. Since the same subjects heard similar booms both inside and outside the house, comparative ratings of indoor and outdoor annoyance were obtained. For a given metric level, indoor subjects gave higher annoyance scores than outdoor subjects. For a given boom; annoyance scores inside were on average the same as those outside. In a post-test questionnaire, the majority of subjects rated the indoor booms as more annoying than the outdoor ones. These results are discussed in this paper.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216685 , L-19846 , NF1676L-10465
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  • 14
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    Vortex Shedding Inside a Baffled Air Duct (2010)
    In:  CASI
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    Publikationsdatum: 2019-08-13
    Beschreibung: Common in the operation of both segmented and un-segmented large solid rocket motors is the occurrence of vortex shedding within the motor chamber. A portion of the energy within a shed vortex is converted to acoustic energy, potentially driving the longitudinal acoustic modes of the motor in a quasi-discrete fashion. This vortex shedding-acoustic mode excitation event occurs for every Reusable Solid Rocket Motor (RSRM) operation, giving rise to subsequent axial thrust oscillations. In order to better understand this vortex shedding/acoustic mode excitation phenomena, unsteady CFD simulations were run for both a test geometry and the full scale RSRM geometry. This paper covers the results from the subscale geometry runs, which were based on work focusing on the RSRM hydrodynamics. Unsteady CFD simulation parameters, including boundary conditions and post-processing returns, are reviewed. The results were further post-processed to identify active acoustic modes and vortex shedding characteristics. Probable locations for acoustic energy generation, and subsequent acoustic mode excitation, are discussed.
    Schlagwort(e): Acoustics
    Materialart: M10-1085 , 27th Rocket Technology (RNTS); Dec 06, 2010 - Dec 10, 2010; Orlando, FL; United States|36th Explosives Development and Characterization (PEDCS); Dec 06, 2010 - Dec 10, 2010; Orlando, FL; United States|JANNAF Joint Propulsion Committee Meeting; Dec 06, 2010 - Dec 10, 2010; Orlando, FL; United States|40th Structures and Mechanical Behavior (SMBS); Dec 06, 2010 - Dec 10, 2010; Orlando, FL; United States
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  • 15
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    Propulsion Noise Reduction Concepts and Progress (2010)
    In:  CASI
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    Publikationsdatum: 2019-08-13
    Beschreibung: Reducing aircraft noise emissions is an important part of the ongoing efforts to make commercial aviation more environmentally friendly. As a major contributor to the overall noise produced by an aircraft, reducing propulsion noise is a pivotal element of any strategy for developing the quiet aircraft of the future. To that end, the NASA Subsonic Fixed Wing project and the Environmentally Responsible Aviation project have been funding basic and system level research into low-noise propulsion technologies that can meet the challenging noise goals set for the future subsonic transport aircraft. This presentation will provide a brief overview of the current research undertaken by NASA in developing noise reduction technologies for both the ultra high bypass ratio turbofans and open rotor systems.
    Schlagwort(e): Acoustics
    Materialart: E-17590 , Green Aviation Summit; Sep 08, 2010 - Sep 09, 2010; Moffett Field, CA; United States
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  • 16
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    Acoustic-Modal Testing of the Ares I Launch Abort System Attitude Control Motor Valve (2010)
    In:  Other Sources
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    Publikationsdatum: 2019-08-13
    Beschreibung: The Attitude Control Motor (ACM) is being developed for use in the Launch Abort System (LAS) of NASA's Ares I launch vehicle. The ACM consists of a small solid rocket motor and eight actuated pintle valves that directionally allocate.thrust_- 1t.has-been- predicted-that significant unsteady. pressure.fluctuations.will.exist. inside the-valves during operation. The dominant frequencies of these oscillations correspond to the lowest several acoustic natural frequencies of the individual valves. An acoustic finite element model of the fluid volume inside the valve has been critical to the prediction of these frequencies and their associated mode shapes. This work describes an effort to experimentally validate the acoustic finite model of the valve with an acoustic modal test. The modal test involved instrumenting a flight-like valve with six microphones and then exciting the enclosed air with a loudspeaker. The loudspeaker was configured to deliver broadband noise at relatively high sound pressure levels. The aquired microphone signals were post-processed and compared to results generated from the acoustic finite element model. Initial comparisons between the test data and the model results revealed that additional model refinement was necessary. Specifically, the model was updated to implement a complex impedance boundary condition at the entrance to the valve supply tube. This boundary condition models the frequency-dependent impedance that an acoustic wave will encounter as it reaches the end of the supply tube. Upon invoking this boundary condition, significantly improved agreement between the test data and the model was realized.
    Schlagwort(e): Acoustics
    Materialart: M10-0184 , 4th Spacecraft Propulsion Joint Subcommittee Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|5th Liquid Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|57th JANNAF Joint Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|7th Modeling and Simulation Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States
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  • 17
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    Internal Acoustics of a Pintle Valve with Supercritical Helium Flow (2010)
    In:  Other Sources
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    Publikationsdatum: 2019-08-13
    Beschreibung: Large amplitude flow unsteadiness is a common phenomenon within the high flow rate ducts and valves associated with propulsion systems. Boundary layer noise, shear layers and vortex shedding are a few of the many sources of flow oscillations. The presence of lightly damped acoustic modes can organize and amplify these sources of flow perturbation, causing undesirable loading of internal parts. The present study investigates the self-induced acoustic environment within a pintle valve subject to high Reynolds Number flow of helium gas. Experiments were conducted to measure the internal pressure oscillations of the Ares I Launch Abort System (LAS) Attitude Control Motor (ACM) valve. The AGM consists of a solid propellant gas generator with eight pintle valves attached to the aft end. The pintle valve is designed to deliver variable upstream conditions to an attache( converging diverging nozzle. In order to investigate the full range of operating conditions 28 separate tests were conducted with varying pintle position and upstream pressure. Helium gas was utilized in order to closely mimic the speed of sound of the gas generator exhaust, minimizing required scaling during data analysis. The recordec pressure measurements were interrogated to multiple ends. The development of root mean square (RMS) value! versus Reynolds Number and Pintle position are important to creating bounding unsteady load curves for valve internal parts. Spectral analysis was also performed, helping to identify power spectral densities (PSD) of acoustic natural frequencies and boundary layer noise. An interesting and unexpected result was the identification of an acoustic mode within the valve which does not respond until the valve was over 60% open. Further, the response amplitude around this mode can be as large or larger than those associated with lower frequency modes.
    Schlagwort(e): Acoustics
    Materialart: M10-0185 , 57th JANNAF Joint Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|7th Modeling and Simulation Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|4th Spacecraft Propulsion Joint Subcommittee Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States|5th Liquid Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States
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  • 18
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    Air-coupled acoustic thermography for in-situ evaluation (2010)
    In:  CASI
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    Publikationsdatum: 2019-08-28
    Beschreibung: Acoustic thermography uses a housing configured for thermal, acoustic and infrared radiation shielding. For in-situ applications, the housing has an open side adapted to be sealingly coupled to a surface region of a structure such that an enclosed chamber filled with air is defined. One or more acoustic sources are positioned to direct acoustic waves through the air in the enclosed chamber and towards the surface region. To activate and control each acoustic source, a pulsed signal is applied thereto. An infrared imager focused on the surface region detects a thermal image of the surface region. A data capture device records the thermal image in synchronicity with each pulse of the pulsed signal such that a time series of thermal images is generated. For enhanced sensitivity and/or repeatability, sound and/or vibrations at the surface region can be used in feedback control of the pulsed signal applied to the acoustic sources.
    Schlagwort(e): Acoustics
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  • 19
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    Deconvolution methods and systems for the mapping of acoustic sources from phased microphone arrays (2010)
    In:  CASI
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    Publikationsdatum: 2019-08-28
    Beschreibung: A method and system for mapping acoustic sources determined from a phased microphone array. A plurality of microphones are arranged in an optimized grid pattern including a plurality of grid locations thereof. A linear configuration of N equations and N unknowns can be formed by accounting for a reciprocal influence of one or more beamforming characteristics thereof at varying grid locations among the plurality of grid locations. A full-rank equation derived from the linear configuration of N equations and N unknowns can then be iteratively determined. A full-rank can be attained by the solution requirement of the positivity constraint equivalent to the physical assumption of statically independent noise sources at each N location. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with the phased microphone array in order to compile an output presentation thereof, thereby removing the beamforming characteristics from the resulting output presentation.
    Schlagwort(e): Acoustics
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  • 20
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    Effect of Microjet Injection on Supersonic Jet Noise (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The effect of microjet (jet) injection on the noise from supersonic jets is investigated. Three convergent-divergent (C-D) nozzles and one convergent nozzle, all having the same exit diameters, are used in the study. The jets are injected perpendicular to the primary jet close to the nozzle lip from six equally-spaced ports having a jet-to-primary-jet diameter ratio of 0.0054. Effects in the over-expanded, fully expanded as well as underexpanded flow regimes are explored. Relative to the effect on subsonic jets, larger reductions in the overall sound pressure level (OASPL) are achieved in most supersonic conditions. The largest reductions are typically associated with suppression of screech and transonic tones. For a shock-free, fully expanded case, the OASPL reductions achieved are comparable to that in the subsonic case; the same correlation, found for subsonic jet noise reduction at shallow observation angle, applies.
    Schlagwort(e): Acoustics
    Materialart: E-17967 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    KSC VAB Aeroacoustic Hazard Assessment (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: NASA Kennedy Space Center (KSC) carried out an analysis of the effects of aeroacoustics produced by stationary solid rocket motors in processing areas at KSC. In the current paper, attention is directed toward the acoustic effects of a motor burning within the Vehicle Assembly Building (VAB). The analysis was carried out with support from ASRC Aerospace who modeled transmission effects into surrounding facilities. Calculations were done using semi-analytical models for both aeroacoustics and transmission. From the results it was concluded that acoustic hazards in proximity to the source of ignition and plume can be severe; acoustic hazards in the far-field are significantly lower.
    Schlagwort(e): Acoustics
    Materialart: KSC-2010-112 , DDESB Seminar/DOD; Jul 13, 2010 - Jul 15, 2010; Portland, OR; United States
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  • 22
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    Phased Array Noise Source Localization Measurements of an F404 Nozzle Plume at Both Full and Model Scale (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A 48-microphone planar phased array system was used to acquire jet noise source localization data on both a full-scale F404-GE-F400 engine and on a 1/4th scale model of a F400 series nozzle. The full-scale engine test data show the location of the dominant noise sources in the jet plume as a function of frequency for the engine in both baseline (no chevron) and chevron configurations. Data are presented for the engine operating both with and without afterburners. Based on lessons learned during this test, a set of recommendations are provided regarding how the phased array measurement system could be modified in order to obtain more useful acoustic source localization data on high-performance military engines in the future. The data obtained on the 1/4th scale F400 series nozzle provide useful insights regarding the full-scale engine jet noise source mechanisms, and document some of the differences associated with testing at model-scale versus fullscale.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216366 , GT2010-22601 , E-17302 , Turbo Expo 2010; Jun 14, 2010 - Jun 18, 2010; Glasgow, Scotland; United Kingdom
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  • 23
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    Lift-Off Acoustics Prediction of Clustered Rocket Engines in the Near Field (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This slide presentation presents a method of predicting acoustics during lift-off of the clustered rocket engines in the near field. Included is a definition of the near field, and the use of deflectors and shielding. There is discussion about the use of PAD, a software system designed to calculate the acoustic levels from the lift of of clustered rocket enginee, including updates to extend the calculation to directivity, water suppression, and clustered nozzles.
    Schlagwort(e): Acoustics
    Materialart: KSC-2010-081 , Spacecraft and Launch Vehicle Dynamic Environments Workshop; Jun 08, 2010 - Jun 10, 2010; El Segundo, CA; United States
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    Noise Budget for the X-Ray Microcalorimeter Spectrometer (XMS) Core Array (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: The purpose of this document is to present and archive the noise budget for the XMS detector, in order, at this stage in mission planning, to learn the scale of the requirements placed on the other instrument subsystems. This document mainly concerns the core array, specifically the baseline version that emerged from the trade studies associated with the ESA Phase A study report. Qualitative extension to the Hydra approach to the outer array is included at the end.
    Schlagwort(e): Acoustics
    Materialart: IXO-TN-001141
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  • 25
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    Predictions of Supersonic Jet Mixing and Shock-Associated Noise Compared With Measured Far-Field Data (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: Codes for predicting supersonic jet mixing and broadband shock-associated noise were assessed using a database containing noise measurements of a jet issuing from a convergent nozzle. Two types of codes were used to make predictions. Fast running codes containing empirical models were used to compute both the mixing noise component and the shock-associated noise component of the jet noise spectrum. One Reynolds-averaged, Navier-Stokes-based code was used to compute only the shock-associated noise. To enable the comparisons of the predicted component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise components. Comparisons were made for 1/3-octave spectra and some power spectral densities using data from jets operating at 24 conditions covering essentially 6 fully expanded Mach numbers with 4 total temperature ratios.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216328 , E-17262
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    Developments and Validations of Fully Coupled CFD and Practical Vortex Transport Method for High-Fidelity Wake Modeling in Fixed and Rotary Wing Applications (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A novel Computational Fluid Dynamics (CFD) coupling framework using a conventional Reynolds-Averaged Navier-Stokes (BANS) solver to resolve the near-body flow field and a Particle-based Vorticity Transport Method (PVTM) to predict the evolution of the far field wake is developed, refined, and evaluated for fixed and rotary wing cases. For the rotary wing case, the RANS/PVTM modules are loosely coupled to a Computational Structural Dynamics (CSD) module that provides blade motion and vehicle trim information. The PVTM module is refined by the addition of vortex diffusion, stretching, and reorientation models as well as an efficient memory model. Results from the coupled framework are compared with several experimental data sets (a fixed-wing wind tunnel test and a rotary-wing hover test).
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216697 , NF1676L-10551
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    Research Plans for Improving Understanding of Effects of Very Low-Frequency Noise of Heavy Lift Rotorcraft (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: This report reviews the English-language technical literature on infrasonic and low-frequency noise effects; identifies the most salient effects of noise produced by a future large civil tiltrotor aircraft on crew, passengers, and communities near landing areas; and recommends research needed to improve understanding of the effects of such noise on passengers, crew, and residents of areas near landing pads.
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216203 , NF1676L-10216
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    Comparison of Comet Enflow and VA One Acoustic-to-Structure Power Flow Predictions (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Comet Enflow is a commercially available, high frequency vibroacoustic analysis software based on the Energy Finite Element Analysis (EFEA). In this method the same finite element mesh used for structural and acoustic analysis can be employed for the high frequency solutions. Comet Enflow is being validated for a floor-equipped composite cylinder by comparing the EFEA vibroacoustic response predictions with Statistical Energy Analysis (SEA) results from the commercial software program VA One from ESI Group. Early in this program a number of discrepancies became apparent in the Enflow predicted response for the power flow from an acoustic space to a structural subsystem. The power flow anomalies were studied for a simple cubic, a rectangular and a cylindrical structural model connected to an acoustic cavity. The current investigation focuses on three specific discrepancies between the Comet Enflow and the VA One predictions: the Enflow power transmission coefficient relative to the VA One coupling loss factor; the importance of the accuracy of the acoustic modal density formulation used within Enflow; and the recommended use of fast solvers in Comet Enflow. The frequency region of interest for this study covers the one-third octave bands with center frequencies from 16 Hz to 4000 Hz.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216191 , L-19820 , LF99-9940
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    Open Rotor Noise Prediction at NASA Langley - Capabilities, Research and Development (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: The high fuel prices of recent years have caused the operating cost of the airlines to soar. In an effort to bring down the fuel consumption, the major aircraft engine manufacturers are now taking a fresh look at open rotors for the propulsion of future airliners. Open rotors, also known as propfans or unducted fans, can offer up to 30 per cent improvement in efficiency compared to high bypass engines of 1980 vintage currently in use in most civilian aircraft. NASA Langley researchers have contributed significantly to the development of aeroacoustic technology of open rotors. This report discusses the current noise prediction technology at Langley and reviews the input data requirements, strengths and limitations of each method as well as the associated problems in need of attention by the researchers. We present a brief history of research on the aeroacoustics of rotating blade machinery at Langley Research Center. We then discuss the available noise prediction codes for open rotors developed at NASA Langley and their capabilities. In particular, we present the two useful formulations used for the computation of noise from subsonic and supersonic surfaces. Here we discuss the open rotor noise prediction codes ASSPIN and one based on Ffowcs Williams-Hawkings equation with penetrable data surface (FW - Hpds). The scattering of sound from surfaces near the rotor are calculated using the fast scattering code (FSC) which is also discussed in this report. Plans for further improvements of these codes are given.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216178 , L-19770 , LF99-9570
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    Acoustics Critical Readiness Review (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: This presentation reviews the status of the acoustic equipment from the medical operations perspective. Included is information about the acoustic dosimeters, sound level meter, and headphones that are planned for use while on orbit. Finally there is information about on-orbit hearing assessments.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-19881
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    Landing Gear Components Noise Study - PIV and Hot-Wire Measurements (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: PIV and hot-wire measurements of the wake flow from rods and bars are presented. The test models include rods of different diameters and cross sections and a rod juxtaposed to a plate. The latter is representative of the latch door that is attached to an aircraft landing gear when the gear is deployed, while the single and multiple rod configurations tested are representative of some of the various struts and cables configuration present on an aircraft landing gear. The test set up is described and the flow measurements are presented. The effect of model surface treatment and freestream turbulence on the spanwise coherence of the vortex shedding is studied for several rod and bar configurations.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216209 , L-19839 , NF1676L-10288
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    Aeromechanics and Aeroacoustics Predictions of the Boeing-SMART Rotor Using Coupled-CFD/CSD Analyses (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This paper will highlight helicopter aeromechanics and aeroacoustics prediction capabilities developed by Georgia Institute of Technology, the Pennsylvania State University, and Northern Arizona University under the Helicopter Quieting Program (HQP) sponsored by the Tactical Technology Office of the Defense Advanced Research Projects Agency (DARPA). First initiated in 2004, the goal of the HQP was to develop high fidelity, state-of-the-art computational tools for designing advanced helicopter rotors with reduced acoustic perceptibility and enhanced performance. A critical step towards achieving this objective is the development of rotorcraft prediction codes capable of assessing a wide range of helicopter configurations and operations for future rotorcraft designs. This includes novel next-generation rotor systems that incorporate innovative passive and/or active elements to meet future challenging military performance and survivability goals.
    Schlagwort(e): Acoustics
    Materialart: ARC-E-DAA-TN910 , AHS 66th Annual Forum and Technology Display; May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
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    Emergent Adaptive Noise Reduction from Communal Cooperation of Sensor Grid (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: In the last decade, the realization of small, inexpensive, and powerful devices with sensors, computers, and wireless communication has promised the development of massive sized sensor networks with dense deployments over large areas capable of high fidelity situational assessments. However, most management models have been based on centralized control and research has concentrated on methods for passing data from sensor devices to the central controller. Most implementations have been small but, as it is not scalable, this methodology is insufficient for massive deployments. Here, a specific application of a large sensor network for adaptive noise reduction demonstrates a new paradigm where communities of sensor/computer devices assess local conditions and make local decisions from which emerges a global behaviour. This approach obviates many of the problems of centralized control as it is not prone to single point of failure and is more scalable, efficient, robust, and fault tolerant
    Schlagwort(e): Acoustics
    Materialart: NF1676L-10827 , Fusion 2010; Jul 26, 2010 - Jul 29, 2010; Edinburgh; United Kingdom
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    Effects of Flow Profile on Educed Acoustic Liner Impedance (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: This paper presents results of an investigation of the effects of shear flow profile on impedance eduction processes employed at NASA Langley. Uniform and 1-D shear-flow propagation models are used to educe the acoustic impedance of three test liners based on aeroacoustic data acquired in the Langley Grazing Flow Impedance Tube, at source levels of 130, 140 and 150 dB, and at centerline Mach numbers of 0.0, 0.3 and 0.5. A ceramic tubular, calibration liner is used to evaluate the propagation models, as this liner is expected to be insensitive to SPL, grazing flow Mach number, and flow profile effects. The propagation models are then used to investigate the effects of shear flow profile on acoustic impedances educed for two conventional perforate-over-honeycomb liners. Results achieved with the uniform-flow models follow expected trends, but those educed with the 1-D shear-flow model do not, even for the calibration liner. However, when the flow profile used with the shear-flow model is varied to increase the Mach number gradient near the wall, results computed with the shear-flow model are well matched to those achieved with the uniform-flow model. This indicates the effects of flow profile on educed acoustic liner impedance are small, but more detailed investigations of the flow field throughout the duct are needed to better understand these effects.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-3763 , LF1676L-10815 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Explanation of Anomalous Behavior Observed in Impedance Eduction Techniques Using Measured Data (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Several enhancements that improve the accuracy and robustness of an impedance eduction technique that use an automatic optimizer are presented. These enhancements are then used to launch an intensive investigation into the cause of anomalous behavior that occurs for a small number of test conditions. This anomalous behavior is investigated for both a hardwall insert and a conventional liner. The primary conclusions of the study are that: (1) for the hard wall insert, the anomalies are due to narrow peaks in the objective function, (2) For the conventional liner, the anomalies are due to the presence of an extremely flat objective function, and (3) the anomalies appear to be triggered by inconsistencies between the duct propagation model and the measured data. At high frequencies, the duct propagation model may need to include the effects of higher-order duct modes, whereas at low frequencies, the effects of the mean boundary layer may have to be included.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9679 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    DAMAS Processing for a Phased Array Study in the NASA Langley Jet Noise Laboratory (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: A jet noise measurement study was conducted using a phased microphone array system for a range of jet nozzle configurations and flow conditions. The test effort included convergent and convergent/divergent single flow nozzles, as well as conventional and chevron dual-flow core and fan configurations. Cold jets were tested with and without wind tunnel co-flow, whereas, hot jets were tested only with co-flow. The intent of the measurement effort was to allow evaluation of new phased array technologies for their ability to separate and quantify distributions of jet noise sources. In the present paper, the array post-processing method focused upon is DAMAS (Deconvolution Approach for the Mapping of Acoustic Sources) for the quantitative determination of spatial distributions of noise sources. Jet noise is highly complex with stationary and convecting noise sources, convecting flows that are the sources themselves, and shock-related and screech noise for supersonic flow. The analysis presented in this paper addresses some processing details with DAMAS, for the array positioned at 90 (normal) to the jet. The paper demonstrates the applicability of DAMAS and how it indicates when strong coherence is present. Also, a new approach to calibrating the array focus and position is introduced and demonstrated.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-3780 , NF1676L-9668 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Validation of a New Procedure for Impedance Eduction in Flow (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: A new impedance eduction procedure is validated by comparing the educed impedance spectrum to that of an older but well-tested eduction procedure. The older procedure requires the installation of a microphone array in the liner test section but the new procedure removes this requirement. A 12.7-mm stainless steel plate and a conventional liner consisting of a perforated plate bonded to a honeycomb core are tested. Test data is acquired from a grazing flow, impedance tube facility for a range of source frequencies and mean flow Mach numbers for which only plane waves are cut on. For the stainless steel plate, the educed admittance spectrum using the new procedure shows an improvement over that of the old procedure. This improvement shows up primarily in the educed conductance spectrum. Both eduction procedures show discrepancies in educed admittance in the mid-frequency range. Indications are that this discrepancy is triggered by an inconsistency between the measured eduction data (that contains boundary layer effects) and the two eduction models (for which the boundary layer is neglected). For the conventional liner, both eduction procedures are in very good agreement with each other. Small discrepancies occur for one or two frequencies in the mid-frequency range and for frequencies beyond the cut on frequency of higher-order duct modes. This discrepancy in the midfrequency range occurs because an automated optimizer is used to educe the impedance and the objective function used by the optimizer is extremely flat and therefore sensitive to initial starting values. The discrepancies at frequencies beyond the cut on frequency of higher order duct modes are due to the assumption of only plane waves in the impedance eduction model, although higher order modes are propagating in the impedance tube facility.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9678 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm, Sweden; Sweden
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    Prediction of Landing Gear Noise Reduction and Comparison to Measurements (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Noise continues to be an ongoing problem for existing aircraft in flight and is projected to be a concern for next generation designs. During landing, when the engines are operating at reduced power, the noise from the airframe, of which landing gear noise is an important part, is equal to the engine noise. There are several methods of predicting landing gear noise, but none have been applied to predict the change in noise due to a change in landing gear design. The current effort uses the Landing Gear Model and Acoustic Prediction (LGMAP) code, developed at The Pennsylvania State University to predict the noise from landing gear. These predictions include the influence of noise reduction concepts on the landing gear noise. LGMAP is compared to wind tunnel experiments of a 6.3%-scale Boeing 777 main gear performed in the Quiet Flow Facility (QFF) at NASA Langley. The geometries tested in the QFF include the landing gear with and without a toboggan fairing and the door. It is shown that LGMAP is able to predict the noise directives and spectra from the model-scale test for the baseline configuration as accurately as current gear prediction methods. However, LGMAP is also able to predict the difference in noise caused by the toboggan fairing and by removing the landing gear door. LGMAP is also compared to far-field ground-based flush-mounted microphone measurements from the 2005 Quiet Technology Demonstrator 2 (QTD 2) flight test. These comparisons include a Boeing 777-300ER with and without a toboggan fairing that demonstrate that LGMAP can be applied to full-scale flyover measurements. LGMAP predictions of the noise generated by the nose gear on the main gear measurements are also shown.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9665 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Hybrid Wing Body Aircraft System Noise Assessment with Propulsion Airframe Aeroacoustic Experiments (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: A system noise assessment of a hybrid wing body configuration was performed using NASA s best available aircraft models, engine model, and system noise assessment method. A propulsion airframe aeroacoustic effects experimental database for key noise sources and interaction effects was used to provide data directly in the noise assessment where prediction methods are inadequate. NASA engine and aircraft system models were created to define the hybrid wing body aircraft concept as a twin engine aircraft with a 7500 nautical mile mission. The engines were modeled as existing technology high bypass ratio turbofans. The baseline hybrid wing body aircraft was assessed at 22 dB cumulative below the FAA Stage 4 certification level. To determine the potential for noise reduction with relatively near term technologies, seven other configurations were assessed beginning with moving the engines two fan nozzle diameters upstream of the trailing edge and then adding technologies for reduction of the highest noise sources. Aft radiated noise was expected to be the most challenging to reduce and, therefore, the experimental database focused on jet nozzle and pylon configurations that could reduce jet noise through a combination of source reduction and shielding effectiveness. The best configuration for reduction of jet noise used state-of-the-art technology chevrons with a pylon above the engine in the crown position. This configuration resulted in jet source noise reduction, favorable azimuthal directivity, and noise source relocation upstream where it is more effectively shielded by the limited airframe surface, and additional fan noise attenuation from acoustic liner on the crown pylon internal surfaces. Vertical and elevon surfaces were also assessed to add shielding area. The elevon deflection above the trailing edge showed some small additional noise reduction whereas vertical surfaces resulted in a slight noise increase. With the effects of the configurations from the database included, the best available noise reduction was 40 dB cumulative. Projected effects from additional technologies were assessed for an advanced noise reduction configuration including landing gear fairings and advanced pylon and chevron nozzles. Incorporating the three additional technology improvements, an aircraft noise is projected of 42.4 dB cumulative below the Stage 4 level.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-3913 , NF1676L-9661 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Acoustic Measurements for Small Solid Rocket Motors (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Models have been developed to predict large solid rocket motor acoustic loads based on the scaling of small solid rocket motors. MSFC has measured several small solid rocket motors in horizontal and launch configurations to anchor these models. Solid Rocket Test Motor (SRTM) has ballistics similar to the Reusable Solid Rocket Motor (RSRM) therefore a good choice for acoustic scaling. Acoustic measurements were collected during the test firing of the Insulation Configuration Extended Length (ICXL) 7,6, and 8 (in firing order) in order to compare to RSRM horizontal firing data. The scope of this presentation includes: Acoustic test procedures and instrumentation implemented during the three SRTM firings and Data analysis method and general trends observed in the data.
    Schlagwort(e): Acoustics
    Materialart: 159th ASA Meeting and Noise-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Rocket Motor Microphone Investigation (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: At ATK's facility in Utah, large full-scale solid rocket motors are tested. The largest is a five-segment version of the reusable solid rocket motor, which is for use on the Ares I launch vehicle. As a continuous improvement project, ATK and BYU investigated the use of microphones on these static tests, the vibration and temperature to which the instruments are subjected, and in particular the use of vent tubes and the effects these vents have at low frequencies.
    Schlagwort(e): Acoustics
    Materialart: M10-0485 , 159th Meeting of the Acoustical Society of America and NOISE-CON 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Direct CFD Predictions of Low Frequency Sounds Generated by a Helicopter Main Rotor (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The use of CFD to directly predict helicopter main rotor noise is shown to be quite promising as an alternative mean for low frequency source noise evaluation. Results using existing state-of-the-art grid structures and finite-difference schemes demonstrated that small perturbation pressures, associated with acoustics radiation, can be extracted with some degree of fidelity. Accuracy of the predictions are demonstrated via comparing to predictions from conventional acoustic analogy-based models, and with measurements obtained from wind tunnel and flight tests for the MD-902 helicopter at several operating conditions. Findings show that the direct CFD approach is quite successfully in yielding low frequency results due to thickness and steady loading noise mechanisms. Mid-to-high frequency contents, due to blade-vortex interactions, are not predicted due to CFD modeling and grid constraints.
    Schlagwort(e): Acoustics
    Materialart: ARC-E-DAA-TN1528 , 2010 American Helicopter Society 66th Annual Forum; May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
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    Acoustic Calibration of the Exterior Effects Room at the NASA Langley Research Center (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The Exterior Effects Room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional audio and visual environment. The 3D audio system consists of 27 mid and high frequency satellite speakers and 4 subwoofers, driven by a real-time audio server running an implementation of Vector Base Amplitude Panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, baffled/unbaffled), and cross-over filtering.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9844 , Joint 159th Meeting of the Acoustical Society of America and Noise-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Toward Establishing a Realistic Benchmark for Airframe Noise Research: Issues and Challenges (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The availability of realistic benchmark configurations is essential to enable the validation of current Computational Aeroacoustic (CAA) methodologies and to further the development of new ideas and concepts that will foster the technologies of the next generation of CAA tools. The selection of a real-world configuration, the subsequent design and fabrication of an appropriate model for testing, and the acquisition of the necessarily comprehensive aeroacoustic data base are critical steps that demand great care and attention. In this paper, a brief account of the nose landing-gear configuration, being proposed jointly by NASA and the Gulfstream Aerospace Company as an airframe noise benchmark, is provided. The underlying thought processes and the resulting building block steps that were taken during the development of this benchmark case are given. Resolution of critical, yet conflicting issues is discussed - the desire to maintain geometric fidelity versus model modifications required to accommodate instrumentation; balancing model scale size versus Reynolds number effects; and time, cost, and facility availability versus important parameters like surface finish and installation effects. The decisions taken during the experimental phase of a study can significantly affect the ability of a CAA calculation to reproduce the prevalent flow conditions and associated measurements. For the nose landing gear, the most critical of such issues are highlighted and the compromises made to resolve them are discussed. The results of these compromises will be summarized by examining the positive attributes and shortcomings of this particular benchmark case.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-10008 , IUTAM Symposium on Computational Aero-Acoustics for Aircraft Noise Prediction; Mar 29, 2010 - Mar 31, 2010; Southampton; United Kingdom
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    An Analytical Assessment of NASA's N(+)1 Subsonic Fixed Wing Project Noise Goal (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The Subsonic Fixed Wing Project of NASA s Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called "N+1" aircraft--designated in NASA vernacular as such since they will follow the current, in-service, "N" airplanes--are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are empirically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216085 , AIAA Paper 2009-3144 , E-17129 , 15th AIAA/CEAS Aeronautics Conference (30th AIAA Aeronautics Conference); May 11, 2009 - May 13, 2009; Miami, FL; United States
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    The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.
    Schlagwort(e): Acoustics
    Materialart: RASD2010-026 , NF1676L-10149 , 10th International Conference on Recent Advances in Structural Dynamics (RASD 2010); Jul 12, 2010 - Jul 14, 2010; Southampton; United Kingdom
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    A Study of Acoustic Reflections in Full-Scale Rotor Low Frequency Noise Measurements Acquired in Wind Tunnels (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Difficulties in obtaining full-scale rotor low frequency noise measurements in wind tunnels are addressed via residual sound reflections due to non-ideal anechoic wall treatments. Examples illustrated with the Boeing-SMART rotor test in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel facility demonstrated that these reflections introduced distortions in the measured acoustic time histories that are not representative of free-field rotor noise radiation. A simplified reflection analysis, based on the method of images, is used to examine the sound measurement quality in such "less-than-anechoic" environment. Predictions of reflection-adjusted acoustic time histories are qualitatively shown to account for some of the spurious fluctuations observed in wind tunnel noise measurements
    Schlagwort(e): Acoustics
    Materialart: ARC-E-DAA-TN1156 , American Helicopter Society Specialists'' Conference on Aeromechanics; Jan 20, 2010 - Jan 22, 2010; San Francisco, CA; United States
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    The Prediction of Broadband Shock-Associated Noise from Dualstream and Rectangular Jets Using RANS CFD (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Supersonic jets operating off-design produce broadband shock-associated noise. Broadband shock-associated noise is characterized by multiple broadband peaks in the far-field and is often the dominant source of noise towards the sideline and upstream direction relative to the jet axis. It is due to large scale coherent turbulence structures in the jet shear layers interacting with the shock cell structure. A broadband shock-associated noise model recently developed by the authors predicts this noise component from solutions to the Reynolds averaged Navier-Stokes equations using a two-equation turbulence model. The broadband shock-associated noise model is applied to dualstream and rectangular nozzles operating supersonically, heated, and off-design. The dualstream jet broadband shock-associated noise predictions are conducted for cases when the core jet is supersonic and the fan jet is subsonic, the core jet is subsonic and the fan jet is supersonic, and when both jet streams operate supersonically. Rectangular jet predictions are shown for a convergent-divergent nozzle operating both over- and under-expanded for cold and heated conditions. The original model implementation has been heavily modified to make accurate predictions for the dualstream jets. It is also argued that for over-expanded jets the oblique shock wave attached to the nozzle lip contributes little to broadband shock-associated noise. All predictions are compared with experiments.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9666 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Propulsion Airframe Aeroacoustic Integration Effects for a Hybrid Wing Body Aircraft Configuration (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: An extensive experimental investigation was performed to study the propulsion airframe aeroacoustic effects of a high bypass ratio engine for a hybrid wing body aircraft configuration where the engine is installed above the wing. The objective was to provide an understanding of the jet noise shielding effectiveness as a function of engine gas condition and location as well as nozzle configuration. A 4.7% scale nozzle of a bypass ratio seven engine was run at characteristic cycle points under static and forward flight conditions. The effect of the pylon and its orientation on jet noise was also studied as a function of bypass ratio and cycle condition. The addition of a pylon yielded significant spectral changes lowering jet noise by up to 4dB at high polar angles and increasing it by 2 to 3dB at forward angles. In order to assess jet noise shielding, a planform representation of the airframe model, also at 4.7% scale was traversed relative to the jet nozzle from downstream to several diameters upstream of the wing trailing edge. Installations at two fan diameters upstream of the wing trailing edge provided only limited shielding in the forward arc at high frequencies for both the axisymmetric and a conventional round nozzle with pylon. This was consistent with phased array measurements suggesting that the high frequency sources are predominantly located near the nozzle exit and, consequently, are amenable to shielding. The mid to low frequencies sources were observed further downstream and shielding was insignificant. Chevrons were designed and used to impact the distribution of sources with the more aggressive design showing a significant upstream migration of the sources in the mid frequency range. Furthermore, the chevrons reduced the low frequency source levels and the typical high frequency increase due to the application of chevron nozzles was successfully shielded. The pylon was further modified with a technology that injects air through the shelf of the pylon which was effective in reducing low frequency noise and moving jet noise sources closer to the nozzle exit. In general, shielding effectiveness varied as a function of cycle condition with the cutback condition producing higher shielding compared to sideline power. The configuration with a more strongly immersed chevron and a pylon oriented opposite to the microphones produced the largest reduction in jet noise. In addition to the jet noise source, the shielding of a broadband point noise source was documented with up to 20 dB of noise reduction at directivity angles directly under the shielding surface.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9660 , AIAA 2010-3912 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Bruel and Kjaer 4944 Microphone Grid Frequency Response Function System Identification (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Br el & Kjaer (B&K) 4944B pressure field microphone was judiciously selected to measure acoustic environments, 400Hz 50kHz, in close proximity of the nozzle during multiple firings of solid propellant rocket motors. It is well known that protective grids can affect the frequency response of microphones. B&K recommends operation of the B&K 4944B without a protective grid when recording measurements above 10 to 15 kHz.
    Schlagwort(e): Acoustics
    Materialart: M10-0462 , 159th Meeting of the Acoustical Society of America; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Phased Array Noise Source Localization Measurements Made on a Williams International FJ44 Engine (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: A 48-microphone planar phased array system was used to acquire noise source localization data on a full-scale Williams International FJ44 turbofan engine. Data were acquired with the array at three different locations relative to the engine, two on the side and one in front of the engine. At the two side locations the planar microphone array was parallel to the engine centerline; at the front location the array was perpendicular to the engine centerline. At each of the three locations, data were acquired at eleven different engine operating conditions ranging from engine idle to maximum (take off) speed. Data obtained with the array off to the side of the engine were spatially filtered to separate the inlet and nozzle noise. Tones occurring in the inlet and nozzle spectra were traced to the low and high speed spools within the engine. The phased array data indicate that the Inflow Control Device (ICD) used during this test was not acoustically transparent; instead, some of the noise emanating from the inlet reflected off of the inlet lip of the ICD. This reflection is a source of error for far field noise measurements made during the test. The data also indicate that a total temperature rake in the inlet of the engine is a source of fan noise.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216228 , AIAA Paper 2009-3183 , E-17215 , 30th AIAA Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States|15th Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States
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    A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semi-Empirical Modeling (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: A new physics-based parameter identification method for rotor harmonic noise sources is developed using an acoustic inverse simulation technique. This new method allows for the identification of individual rotor harmonic noise sources and allows them to be characterized in terms of their individual non-dimensional governing parameters. This new method is applied to both wind tunnel measurements and ground noise measurements of two-bladed rotors. The method is shown to match the parametric trends of main rotor Blade-Vortex Interaction (BVI) noise, allowing accurate estimates of BVI noise to be made for operating conditions based on a small number of measurements taken at different operating conditions.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9562 , AHS International 66th Annual Forum and Technology Display; May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
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    Acoustic Performance of Novel Fan Noise Reduction Technologies for a High Bypass Model Turbofan at Simulated Flights Conditions (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Two novel fan noise reduction technologies, over the rotor acoustic treatment and soft stator vane technologies, were tested in an ultra-high bypass ratio turbofan model in the NASA Glenn Research Center s 9- by 15-Foot Low-Speed Wind Tunnel. The performance of these technologies was compared to that of the baseline fan configuration, which did not have these technologies. Sideline acoustic data and hot film flow data were acquired and are used to determine the effectiveness of the various treatments. The material used for the over the rotor treatment was foam metal and two different types were used. The soft stator vanes had several internal cavities tuned to target certain frequencies. In order to accommodate the cavities it was necessary to use a cut-on stator to demonstrate the soft vane concept.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-215841 , AIAA Paper 2009-3140 , E-17102 , 30th Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States|15th Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States
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    Improved Phased Array Imaging of a Model Jet (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: An advanced phased array system, OptiNav Array 48, and a new deconvolution algorithm, TIDY, have been used to make octave band images of supersonic and subsonic jet noise produced by the NASA Glenn Small Hot Jet Acoustic Rig (SHJAR). The results are much more detailed than previous jet noise images. Shock cell structures and the production of screech in an underexpanded supersonic jet are observed directly. Some trends are similar to observations using spherical and elliptic mirrors that partially informed the two-source model of jet noise, but the radial distribution of high frequency noise near the nozzle appears to differ from expectations of this model. The beamforming approach has been validated by agreement between the integrated image results and the conventional microphone data.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216227 , AIAA Paper 2009-3186 , E-17214 , 15th Aeroacoustics Conference (30th Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States
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    International Space Station Crew Quarters Ventilation and Acoustic Design Implementation (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The International Space Station (ISS) United States Operational Segment has four permanent rack sized ISS Crew Quarters (CQs) providing a private crew member space. The CQs use Node 2 cabin air for ventilation/thermal cooling, as opposed to conditioned ducted air-from the ISS Common Cabin Air Assembly (CCAA) or the ISS fluid cooling loop. Consequently, CQ can only increase the air flow rate to reduce the temperature delta between the cabin and the CQ interior. However, increasing airflow causes increased acoustic noise so efficient airflow distribution is an important design parameter. The CQ utilized a two fan push-pull configuration to ensure fresh air at the crew member's head position and reduce acoustic exposure. The CQ ventilation ducts are conduits to the louder Node 2 cabin aisle way which required significant acoustic mitigation controls. The CQ interior needs to be below noise criteria curve 40 (NC-40). The design implementation of the CQ ventilation system and acoustic mitigation are very inter-related and require consideration of crew comfort balanced with use of interior habitable volume, accommodation of fan failures, and possible crew uses that impact ventilation and acoustic performance. Each CQ required 13% of its total volume and approximately 6% of its total mass to reduce acoustic noise. This paper illustrates the types of model analysis, assumptions, vehicle interactions, and trade-offs required for CQ ventilation and acoustics. Additionally, on-orbit ventilation system performance and initial crew feedback is presented. This approach is applicable to any private enclosed space that the crew will occupy.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-20185 , International Conference on Environmental Systems; Jul 11, 2010 - Jul 15, 2010; Barcelona; Spain
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    Impact of Damping Uncertainty on SEA Model Response Variance (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Statistical Energy Analysis (SEA) is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently, techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainties in the system properties. In the present paper uncertainty in the damping loss factor is propagated through SEA to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a floor-equipped cylindrical test article that resembles an aircraft fuselage. Realistic bounds on the damping loss factor are determined from measurements acquired on the sidewall of the test article. The analysis demonstrates that uncertainties in damping have the potential to significantly impact the mean and variance of the predicted response.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9640 , Joint 159th Meeting of the Acoustical Society of America and Noise-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Validation of a Polyimide Foam Model for Use in Transmission Loss Applications (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The work described in this paper was focused on the use of a new polyimide foam in a double wall sound transmission loss application. Recall that polyimide foams are functionally attractive, compared to polyurethane foams, for example, owing to their fire resistance. The foam considered here was found to have a flow resistivity that was too high for conventional acoustical applications, and as a result, it was processed by partial crushing to lower the flow resistivity into an acceptable range. Procedures for measuring the flow resistivity and Young s modulus of the material have been described, as was an inverse characterization procedure for estimating the remaining Biot parameters based on standing wave tube measurements of transmission loss and absorption coefficient. The inverse characterization was performed using a finite element model implementation of the Biot poro-elastic material theory. Those parameters were then used to predict the sound transmission loss of a double panel system lined with polyimide foam, and the predictions were compared with full-scale transmission loss measurements. The agreement between the two was reasonable, especially in the high and low frequency limits; however, it was found that the SEA model resulted in an under-prediction of the transmission loss in the mid-frequency range. Nonetheless, it was concluded that the performance of polyimide foam could be predicted using conventional poro-elastic material models and that polyimide foam may offer an attractive alternative to other double wall linings in certain situations: e.g., when fire resistance is a key issue. Future work will concentrate on reducing the density of the foam to values similar to those used in current aircraft sidewall treatments, and developing procedures to improve the performance of the foam in transmission loss applications.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-10083 , Joint 159th Meeting of the Acoustical Society of America and Noise-Con 2010; Apr 19, 2010 - Apr 23, 2010; Baltimore, MD; United States
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    Simulation of Turbine Tone Noise Generation Using a Turbomachinery Aerodynamics Solver (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: As turbofan engine bypass ratios continue to increase, the contribution of the turbine to the engine noise signature is receiving more attention. Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. As proof-of-concept for this approach, two highly detailed numerical simulations of the unsteady flow field inside the first stage of a modern high-pressure turbine were carried out. The simulations were computed using TURBO, which is an unsteady Reynolds-Averaged Navier-Stokes code capable of multi-stage simulations. Spectral and modal analysis of the unsteady pressure data from the numerical simulation of the turbine stage show a circumferential modal distribution that is consistent with the Tyler-Sofrin rule. Within the high-pressure turbine, the interaction of velocity, pressure and temperature fluctuations with the downstream blade rows are all possible tone noise source mechanisms. We have taken the initial step in determining the source strength hierarchy by artificially reducing the level of temperature fluctuations in the turbine flowfield. This was accomplished by changing the vane cooling flow temperature in order to mitigate the vane thermal wake in the second of the two simulations. The results indicated that, despite a dramatic change in the vane cooling flow, the computed modal levels changed very little indicating that the contribution of temperature fluctuations to the overall pressure field is rather small compared with the viscous and potential field interaction mechanisms.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216230 , AIAA Paper 2009-3282 , E-17217 , 15th Aeroacoustics Conference (30th Aeroacoustics Conference; May 11, 2009 - May 13, 2009; Miami, FL; United States
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    Jet Noise Reduction by Microjets - A Parametric Study (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The effect of injecting tiny secondary jets (microjets ) on the radiated noise from a subsonic primary jet is studied experimentally. The microjets are injected on to the primary jet near the nozzle exit with variable port geometry, working fluid and driving pressure. A clear noise reduction is observed that improves with increasing jet pressure. It is found that smaller diameter ports with higher driving pressure, but involving less thrust and mass fraction, can produce better noise reduction. A collection of data from the present as well as past experiments is examined in an attempt to correlate the noise reduction with the operating parameters. The results indicate that turbulent mixing noise reduction, as monitored by OASPL at a shallow angle, correlates with the ratio of jet to primary jet driving pressures normalized by the ratio of corresponding diameters (p d /pjD). With gaseous injection, the spectral amplitudes decrease at lower frequencies while an increase is noted at higher frequencies. It is apparent that this amplitude crossover is at least partly due to shock-associated noise from the underexpanded jets themselves. Such crossover is not seen with water injection since the flow in that case is incompressible and there is no shock-associated noise. Centerline velocity data show that larger noise reduction is accompanied by faster jet decay as well as significant reduction in turbulence intensities. While a physical understanding of the dependence of noise reduction on p d /pjD remains unclear, given this correlation, an analysis explains the observed dependence of the effect on various other parameters.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-215846 , AIAA Paper 2009-3129 , E-17112 , 15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference); May 11, 2009 - May 13, 2009; Miami, FL; United States
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    Broadband Fan Noise Prediction System for Turbofan Engines (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the third volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User s Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by validation studies that were done on three fan rigs. It concludes with recommended improvements and additional studies for BFaNS.
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216898/VOL3 , E-17477-3
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    Broadband Fan Noise Prediction System for Turbofan Engines (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the second volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User s Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by step-by-step instructions for installing and running BFaNS. It concludes with technical documentation of the BFaNS computer program.
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216898/VOL2 , E-17477-2
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    Broadband Fan Noise Prediction System for Turbofan Engines (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the first volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User's Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by step-by-step instructions for installing and running Setup_BFaNS. It concludes with technical documentation of the Setup_BFaNS computer program.
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216898/VOL1 , E-17477-1
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    Aerodynamic Design and Computational Analysis of a Spacecraft Cabin Ventilation Fan (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Quieter working environments for astronauts are needed if future long-duration space exploration missions are to be safe and productive. Ventilation and payload cooling fans are known to be dominant sources of noise, with the International Space Station being a good case in point. To address this issue in a cost-effective way, early attention to fan design, selection, and installation has been recommended. Toward that end, NASA has begun to investigate the potential for small-fan noise reduction through improvements in fan aerodynamic design. Using tools and methodologies similar to those employed by the aircraft engine industry, most notably computational fluid dynamics (CFD) codes, the aerodynamic design of a new cabin ventilation fan has been developed, and its aerodynamic performance has been predicted and analyzed. The design, intended to serve as a baseline for future work, is discussed along with selected CFD results
    Schlagwort(e): Acoustics
    Materialart: NASA/CR-2010-216329 , E-17263
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    Frequency coded sensors incorporating tapers (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.
    Schlagwort(e): Acoustics
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    Supersonics Project - Airport Noise Tech Challenge (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The Airport Noise Tech Challenge research effort under the Supersonics Project is reviewed. While the goal of "Improved supersonic jet noise models validated on innovative nozzle concepts" remains the same, the success of the research effort has caused the thrust of the research to be modified going forward in time. The main activities from FY06-10 focused on development and validation of jet noise prediction codes. This required innovative diagnostic techniques to be developed and deployed, extensive jet noise and flow databases to be created, and computational tools to be developed and validated. Furthermore, in FY09-10 systems studies commissioned by the Supersonics Project showed that viable supersonic aircraft were within reach using variable cycle engine architectures if exhaust nozzle technology could provide 3-5dB of suppression. The Project then began to focus on integrating the technologies being developed in its Tech Challenge areas to bring about successful system designs. Consequently, the Airport Noise Tech Challenge area has shifted efforts from developing jet noise prediction codes to using them to develop low-noise nozzle concepts for integration into supersonic aircraft. The new plan of research is briefly presented by technology and timelines.
    Schlagwort(e): Acoustics
    Materialart: E-17637
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    High-Temperature Surface-Acoustic-Wave Transducer (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.
    Schlagwort(e): Acoustics
    Materialart: LEW-18547-1 , NASA Tech Briefs, October 2010; 8
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    Dispersion of Sound in Dilute Suspensions with Nonlinear Particle Relaxation (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of Omega(Tau)(sub d), where Omega is the circular frequency, and Tau(sub d) is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction
    Schlagwort(e): Acoustics
    Materialart: KSC-2010-005
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    Notes on SAW Tag Interrogation Techniques (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: We consider the problem of interrogating a single SAW RFID tag with a known ID and known range in the presence of multiple interfering tags under the following assumptions: (1) The RF propagation environment is well approximated as a simple delay channel with geometric power-decay constant alpha 〉/= 2. (2) The interfering tag IDs are unknown but well approximated as independent, identically distributed random samples from a probability distribution of tag ID waveforms with known second-order properties, and the tag of interest is drawn independently from the same distribution. (3) The ranges of the interfering tags are unknown but well approximated as independent, identically distributed realizations of a random variable rho with a known probability distribution f(sub rho) , and the tag ranges are independent of the tag ID waveforms. In particular, we model the tag waveforms as random impulse responses from a wide-sense-stationary, uncorrelated-scattering (WSSUS) fading channel with known bandwidth and scattering function. A brief discussion of the properties of such channels and the notation used to describe them in this document is given in the Appendix. Under these assumptions, we derive the expression for the output signal-to-noise ratio (SNR) for an arbitrary combination of transmitted interrogation signal and linear receiver filter. Based on this expression, we derive the optimal interrogator configuration (i.e., transmitted signal/receiver filter combination) in the two extreme noise/interference regimes, i.e., noise-limited and interference-limited, under the additional assumption that the coherence bandwidth of the tags is much smaller than the total tag bandwidth. Finally, we evaluate the performance of both optimal interrogators over a broad range of operating scenarios using both numerical simulation based on the assumed model and Monte Carlo simulation based on a small sample of measured tag waveforms. The performance evaluation results not only provide guidelines for proper interrogator design, but also provide some insight on the validity of the assumed signal model. It should be noted that the assumption that the impulse response of the tag of interest is known precisely implies that the temperature and range of the tag are also known precisely, which is generally not the case in practice. However, analyzing interrogator performance under this simplifying assumption is much more straightforward and still provides a great deal of insight into the nature of the problem.
    Schlagwort(e): Acoustics
    Materialart: JSC-CN-20378
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    Leak detection using structure-borne noise (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: A method for detection and location of air leaks in a pressure vessel, such as a spacecraft, includes sensing structure-borne ultrasound waveforms associated with turbulence caused by a leak from a plurality of sensors and cross correlating the waveforms to determine existence and location of the leak. Different configurations of sensors and corresponding methods can be used. An apparatus for performing the methods is also provided.
    Schlagwort(e): Acoustics
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    Acoustic Emission Measurement with Fiber Bragg Gratings for Structure Health Monitoring (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: Structural Health monitoring (SHM) is a way of detecting and assessing damage to large scale structures. Sensors used in SHM for aerospace structures provide real time data on new and propagating damage. One type of sensor that is typically used is an acoustic emission (AE) sensor that detects the acoustic emissions given off from a material cracking or breaking. The use of fiber Bragg grating (FBG) sensors to provide acoustic emission data for damage detection is studied. In this research, FBG sensors are used to detect acoustic emissions of a material during a tensile test. FBG sensors were placed as a strain sensor (oriented parallel to applied force) and as an AE sensor (oriented perpendicular to applied force). A traditional AE transducer was used to collect AE data to compare with the FBG data. Preliminary results show that AE with FBGs can be a viable alternative to traditional AE sensors.
    Schlagwort(e): Acoustics
    Materialart: M09-0682 , 2010 SPIE Smart Structure/NDE; Mar 07, 2010 - Mar 11, 2010; San Diego, CA; United States
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    The Effect of Cross Flow on Slat Noise (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: This paper continues the computational examination (AIAA Journal, Vol. 45, No. 9, 2007, pp. 2174-2186) of the unsteady flow within the slat cove region of a multi-element high-lift airfoil configuration. Two simulations have been performed to examine the effect of cross flow on the near-field fluctuations and far-field acoustics. The cross flow was imposed by changing the free-stream velocity vector and modifying the Reynolds number. The cross flow does appear to alter the dynamics in the cove region, but the impact on the noise seems to be more dependent on the flow conditions. However, separating out the true effects of the cross flow from those of the Mach and Reynolds number would require additional calculations to isolate those effects.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-3835 , NF1676L-9686 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Assessment of Hybrid RANS/LES Turbulence Models for Aeroacoustics Applications (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Predicting the noise from aircraft with exposed landing gear remains a challenging problem for the aeroacoustics community. Although computational fluid dynamics (CFD) has shown promise as a technique that could produce high-fidelity flow solutions, generating grids that can resolve the pertinent physics around complex configurations can be very challenging. Structured grids are often impractical for such configurations. Unstructured grids offer a path forward for simulating complex configurations. However, few unstructured grid codes have been thoroughly tested for unsteady flow problems in the manner needed for aeroacoustic prediction. A widely used unstructured grid code, FUN3D, is examined for resolving the near field in unsteady flow problems. Although the ultimate goal is to compute the flow around complex geometries such as the landing gear, simpler problems that include some of the relevant physics, and are easily amenable to the structured grid approaches are used for testing the unstructured grid approach. The test cases chosen for this study correspond to the experimental work on single and tandem cylinders conducted in the Basic Aerodynamic Research Tunnel (BART) and the Quiet Flow Facility (QFF) at NASA Langley Research Center. These configurations offer an excellent opportunity to assess the performance of hybrid RANS/LES turbulence models that transition from RANS in unresolved regions near solid bodies to LES in the outer flow field. Several of these models have been implemented and tested in both structured and unstructured grid codes to evaluate their dependence on the solver and mesh type. Comparison of FUN3D solutions with experimental data and numerical solutions from a structured grid flow solver are found to be encouraging.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-4001 , NF1676L-9685 , AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Modeling of a Surface Acoustic Wave Strain Sensor (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: NASA Langley Research Center is investigating Surface Acoustic Wave (SAW) sensor technology for harsh environments aimed at aerospace applications. To aid in development of sensors a model of a SAW strain sensor has been developed. The new model extends the modified matrix method to include the response of Orthogonal Frequency Coded (OFC) reflectors and the response of SAW devices to strain. These results show that the model accurately captures the strain response of a SAW sensor on a Langasite substrate. The results of the model of a SAW Strain Sensor on Langasite are presented
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9973 , NanoTech Conference and Expo 2010: Modeling and Simulation of Microsystems; Jun 21, 2010 - Jun 25, 2010; Anaheim, CA; United States
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    On Acoustic Source Specification for Rotor-Stator Interaction Noise Prediction (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This paper describes the use of measured source data to assess the effects of acoustic source specification on rotor-stator interaction noise predictions. Specifically, the acoustic propagation and radiation portions of a recently developed coupled computational approach are used to predict tonal rotor-stator interaction noise from a benchmark configuration. In addition to the use of full measured data, randomization of source mode relative phases is also considered for specification of the acoustic source within the computational approach. Comparisons with sideline noise measurements are performed to investigate the effects of various source descriptions on both inlet and exhaust predictions. The inclusion of additional modal source content is shown to have a much greater influence on the inlet results. Reasonable agreement between predicted and measured levels is achieved for the inlet, as well as the exhaust when shear layer effects are taken into account. For the number of trials considered, phase randomized predictions follow statistical distributions similar to those found in previous statistical source investigations. The shape of the predicted directivity pattern relative to measurements also improved with phase randomization, having predicted levels generally within one standard deviation of the measured levels.
    Schlagwort(e): Acoustics
    Materialart: AIAA Paper 2010-3713 , NF1676L-9687 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Quiet, Efficient Fans for Spaceflight: An Overview of NASA's Technology Development Plan (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A Technology Development Plan to improve the aerodynamic and acoustic performance of spaceflight fans has been submitted to NASA s Exploration Technology Development Program. The plan describes a research program intended to make broader use of the technology developed at NASA Glenn to increase the efficiency and reduce the noise of aircraft engine fans. The goal is to develop a set of well-characterized government-owned fans nominally suited for spacecraft ventilation and cooling systems. NASA s Exploration Life Support community will identify design point conditions for the fans in this study. Computational Fluid Dynamics codes will be used in the design and analysis process. The fans will be built and used in a series of tests. Data from aerodynamic and acoustic performance tests will be used to validate performance predictions. These performance maps will also be entered into a database to help spaceflight fan system developers make informed design choices. Velocity measurements downstream of fan rotor blades and stator vanes will also be collected and used for code validation. Details of the fan design, analysis, and testing will be publicly reported. With access to fan geometry and test data, the small fan industry can independently evaluate design and analysis methods and work towards improvement.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216238 , NC10-075 , E-17225 , NOISE-CON 2010; Apr 19, 2010 - Apr 21, 2010; Baltimore, MD; United States
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    A Computational Study of BVI Noise Reduction Using Active Twist Control (2010)
    In:  Other Sources
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    Publikationsdatum: 2019-07-13
    Beschreibung: The results of a computational study examining the effects of active-twist control on blade-vortex interaction (BVI) noise using the Apache Active Twist Rotor are presented. The primary goal of this activity is to reduce BVI noise during a low-speed descent flight condition using active-twist control. Rotor aeroelastic behavior was modeled using the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics code and the rotor noise was predicted using the acoustics code PSU-WOPWOP. The accuracy of the analysis was validated through comparisons with experimental acoustic data for the first generation Active Twist Rotor at an advance ratio of mu=0.14. The application of active-twist to the main rotor blade system consisted of harmonic actuation frequencies ranging from 2P to 5P, control phase angles from 0' to 360 , and tip-twist amplitudes ranging from 0.5 to 4.0 . The acoustic analysis was conducted for a single low-speed flight condition of advance ratio =0.14 and shaft angle-of-attack, c^=+6 , with BVI noise levels predicted on a flat plane of observers located 1.1 rotor diameters beneath the rotor. The results indicated reductions of up to 11dB in BVI noise using 1.25 tip-twist amplitude with negligible effects on 4P vertical hub shear.
    Schlagwort(e): Acoustics
    Materialart: NF1676L-9435 , American Helicopter Society 66th Annual Forum and Technology Display; May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
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    An Experimental Study of Fan Inflow Distortion Tone Noise (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: The tone noise generated when a fan ingests circumferentially distorted flow was studied by an experiment conducted with the Advanced Noise Control Fan at the NASA Glenn Research Center. The inflow was distorted by inserting cylindrical rods radially into the duct. The rods were arranged in circumferentially irregular patterns in three of the five configurations tested. Rods were held in place using a mounting ring with 30 equally spaced holes placed at an axial location one rotor chordlength upstream of the fan. Acoustic pressure was measured in the inlet and exhaust duct of the fan using the Rotating Rake fan tone measurement system. Sound power levels, calculated from the measured data, were plotted as a function of circumferential mode. An analytic description of the unsteady pressure distribution at the interaction plane between the stationary rods and the fan rotor is presented in a form suitable for representing the circumferentially irregularly placed rods. Terms in the analytical description for sound power were proven to be useful in determining the dominant circumferential modes measured in the experiment and the differences in mode power level between the configurations tested. Insight gained through this work will be useful in the development of tools to compute fan inflow distortion tone noise.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-215844 , AIAA Paper 2009-3290 , E-17106 , 15th Aeroacoustics Conference (30th Aeroacoustics Conference); May 11, 2009 - May 13, 2009; Miami, FL; United States
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    Jet Noise Scaling in Dual Stream Nozzles (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Power spectral laws in dual stream jets are studied by considering such flows a superposition of appropriate single-stream coaxial jets. Noise generation in each mixing region is modeled using spectral power laws developed earlier for single stream jets as a function of jet temperature and observer angle. Similarity arguments indicate that jet noise in dual stream nozzles may be considered as a composite of four single stream jets representing primary/secondary, secondary/ambient, transition, and fully mixed zones. Frequency filter are designed to highlight spectral contribution from each jet. Predictions are provided at an area ratio of 2.0--bypass ratio from 0.80 to 3.40, and are compared with measurements within a wide range of velocity and temperature ratios. These models suggest that the low frequency noise in unheated jets is dominated by the fully mixed region at all velocity ratios, while the high frequency noise is dominated by the secondary when the velocity ratio is larger than 0.80. Transition and fully mixed jets equally dominate the low frequency noise in heated jets. At velocity ratios less than 0.50, the high frequency noise from primary/bypass becomes a significant contributing factor similar to that in the secondary/ambient jet.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216887 , AIAA Paper 2010-3968 , E-17466 , 16th Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
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    Update on Supersonic Jet Noise Research at NASA (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: An update on jet noise research conducted in the Fundamental Aeronautics and Integrated Systems Research Programs was presented. Highlighted research projects included those focused on the development of prediction tools, diagnostic tools, and noise reduction concepts.
    Schlagwort(e): Acoustics
    Materialart: E-17588 , TETS 2010 (Turbine Engine Technology Symposium): Energy Efficient, Mission Capable; Sep 13, 2010 - Sep 16, 2010; Dayton, OH; United States
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    NASA Open Rotor Noise Research (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Owing to their inherent fuel burn efficiency advantage compared with the current generation high bypass ratio turbofan engines, there is resurgent interest in developing open rotor propulsion systems for powering the next generation commercial aircraft. However, to make open rotor systems truly competitive, they must be made to be acoustically acceptable too. To address this challenge, NASA in collaboration with industry is exploring the design space for low-noise open rotor propulsion systems. The focus is on the system level assessment of the open rotors compared with other candidate concepts like the ultra high bypass ratio cycle engines. To that end there is an extensive research effort at NASA focused on component testing and diagnostics of the open rotor acoustic performance as well as assessment and improvement of open rotor noise prediction tools. In this presentation and overview of the current NASA research on open rotor noise will be provided. Two NASA projects, the Environmentally Responsible Aviation Project and the Subsonic Fixed Wing Project, have been funding this research effort.
    Schlagwort(e): Acoustics
    Materialart: E-17589 , 14th CEAS-ASC Workshop; Oct 07, 2010 - Oct 08, 2010; Warsaw; Poland|5th Scientific Workshop of X3-Noise Aeroacoustics of High-Speed Aircraft Propellers and Open Rotors; Oct 07, 2010 - Oct 08, 2010; Warsaw; Poland
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    Drive Rig Mufflers for Model Scale Engine Acoustic Testing (2010)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Testing of air breathing propulsion systems in the 9x15 foot wind tunnel at NASA Glenn Research Center depends on compressed air turbines for power. The drive rig turbines exhaust directly to the wind tunnel test section, and have been found to produce significant unwanted noise that reduces the quality of the acoustic measurements of the model being tested. In order to mitigate this acoustic contamination, a muffler can be attached downstream of the drive rig turbine. The modern engine designs currently being tested produce much less noise than traditional engines, and consequently a lower noise floor is required of the facility. An acoustic test of a muffler designed to mitigate this extraneous noise is presented, and a noise reduction of 8 dB between 700 Hz and 20 kHz was documented, significantly improving the quality of acoustic measurements in the facility.
    Schlagwort(e): Acoustics
    Materialart: E-17577 , Acoustic Technical Working Group Meeting; Oct 21, 2010 - Oct 22, 2010; Hampton, VA; United States
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    Open Rotor Test Status (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Testing of low noise, counter-rotating open rotor propulsion concepts has been ongoing at Glenn Research Center in collaboration with General Electric Company. The presentation is an overview of the testing that has been completed to date and previews the upcoming test entries. The NASA Environmentally Responsible Aviation Project Diagnostics entry is the most recent to finish. That test entry included acoustic phased array, pressure sensitive paint, particle image velocimetry, pylon installed measurements and acoustic shielding measurements. A preview of the data to be acquired in the 8x6 high-speed wind tunnel is also included.
    Schlagwort(e): Acoustics
    Materialart: E-17576 , Acoustics Technical Working Group meeting; Oct 21, 2010 - Oct 22, 2010; Cleveland, OH; United States
    Format: application/pdf
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  • 83
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    Fan and Open-Rotor Noise (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This presentation is a technical progress report and near term outlook for work on fan (in-duct) and open-rotor (high speed propeller) noise funded by NASA's Fundamental Aeronautics Program, Subsonic Fixed Wing (SFW) Project and the Integrated Systems Research Program, Environmentally Responsible Aircraft Project. Sections of the presentation cover: the system level metrics are outlined for the SFW timeframes (2015, 2020 1 2025); the Ultra-High Bypass ratio technology development roadmap; a feasibility study for a low technology readiness level fan test rig; the development plan for a turbomachinery oriented computational aero-acoustics code; and systems analysis work on open-rotor modeling.
    Schlagwort(e): Acoustics
    Materialart: E-17573 , Acoustics Technical Work Group Meeting; Oct 21, 2010 - Oct 22, 2010; Hampton, VA; United States
    Format: application/pdf
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  • 84
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    Core-Noise (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This presentation is a technical progress report and near-term outlook for NASA-internal and NASA-sponsored external work on core (combustor and turbine) noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system level noise metrics for the 2015, 2020, and 2025 timeframes; the emerging importance of core noise and its relevance to the SFW Reduced-Noise-Aircraft Technical Challenge; the current research activities in the core-noise area, with some additional details given about the development of a high-fidelity combustion-noise prediction capability; the need for a core-noise diagnostic capability to generate benchmark data for validation of both high-fidelity work and improved models, as well as testing of future noise-reduction technologies; relevant existing core-noise tests using real engines and auxiliary power units; and examples of possible scenarios for a future diagnostic facility. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The SFW Reduced-Noise-Aircraft Technical Challenge aims to enable concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. This reduction of aircraft noise is critical for enabling the anticipated large increase in future air traffic. Noise generated in the jet engine core, by sources such as the compressor, combustor, and turbine, can be a significant contribution to the overall noise signature at low-power conditions, typical of approach flight. At high engine power during takeoff, jet and fan noise have traditionally dominated over core noise. However, current design trends and expected technological advances in engine-cycle design as well as noise-reduction methods are likely to reduce non-core noise even at engine-power points higher than approach. In addition, future low-emission combustor designs could increase the combustion-noise component. The trend towards high-power-density cores also means that the noise generated in the low-pressure turbine will likely increase. Consequently, the combined result from these emerging changes will be to elevate the overall importance of turbomachinery core noise, which will need to be addressed in order to meet future noise goals.
    Schlagwort(e): Acoustics
    Materialart: E-17572 , Acoustics Technical Working Group; Oct 21, 2010 - Oct 22, 2010; Hampton, VA; United States
    Format: application/pdf
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  • 85
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    On the Scaling of Small, Heat Simulated Jet Noise Measurements to Moderate Size Exhaust Jets (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Modern military aircraft jet engines are designed with variable geometry nozzles to provide optimum thrust in different operating conditions, depending on the flight envelope. However, the acoustic measurements for such nozzles are scarce, due to the cost involved in making full scale measurements and the lack of details about the exact geometry of these nozzles. Thus the present effort at The Pennsylvania State University and the NASA Glenn Research Center- in partnership with GE Aviation is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles. An equally important objective is to validate methodology for using data obtained from small and moderate scale experiments to reliably predict the most important components of full scale engine noise. The experimental results presented show reasonable agreement between small scale and moderate scale jet acoustic data, as well as between heated jets and heat-simulated ones. Unresolved issues however are identified that are currently receiving our attention, in particular the effect of the small bypass ratio airflow. Future activities will identify and test promising noise reduction techniques in an effort to predict how well such concepts will work with full scale engines in flight conditions.
    Schlagwort(e): Acoustics
    Materialart: E-17520 , 16th AIAA/CEAS Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
    Format: application/pdf
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  • 86
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    Data Quality Assurance for Supersonic Jet Noise Measurements (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The noise created by a supersonic aircraft is a primary concern in the design of future high-speed planes. The jet noise reduction technologies required on these aircraft will be developed using scale-models mounted to experimental jet rigs designed to simulate the exhaust gases from a full-scale jet engine. The jet noise data collected in these experiments must accurately predict the noise levels produced by the full-scale hardware in order to be a useful development tool. A methodology has been adopted at the NASA Glenn Research Center s Aero-Acoustic Propulsion Laboratory to insure the quality of the supersonic jet noise data acquired from the facility s High Flow Jet Exit Rig so that it can be used to develop future nozzle technologies that reduce supersonic jet noise. The methodology relies on mitigating extraneous noise sources, examining the impact of measurement location on the acoustic results, and investigating the facility independence of the measurements. The methodology is documented here as a basis for validating future improvements and its limitations are noted so that they do not affect the data analysis. Maintaining a high quality jet noise laboratory is an ongoing process. By carefully examining the data produced and continually following this methodology, data quality can be maintained and improved over time.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216767 , GT2010-22545 , E-17392 , Turbo Expo 2010; Jun 14, 2010 - Jun 18, 2010; Glasgow, Scotland; United Kingdom
    Format: application/pdf
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    The Effect of Nondeterministic Parameters on Shock-Associated Noise Prediction Modeling (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Engineering applications for aircraft noise prediction contain models for physical phenomenon that enable solutions to be computed quickly. These models contain parameters that have an uncertainty not accounted for in the solution. To include uncertainty in the solution, nondeterministic computational methods are applied. Using prediction models for supersonic jet broadband shock-associated noise, fixed model parameters are replaced by probability distributions to illustrate one of these methods. The results show the impact of using nondeterministic parameters both on estimating the model output uncertainty and on the model spectral level prediction. In addition, a global sensitivity analysis is used to determine the influence of the model parameters on the output, and to identify the parameters with the least influence on model output.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216801 , AIAA Paper 2010-3841 , E-17432 , 16th Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
    Format: application/pdf
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    Evaluating the Acoustic Effect of Over-the-Rotor Foam-Metal Liner Installed on a Low Speed Fan Using Virtual Rotating Microphone Imaging (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: An in-duct beamforming technique for imaging rotating broadband fan sources has been used to evaluate the acoustic characteristics of a Foam-Metal Liner installed over-the-rotor of a low-speed fan. The NASA Glenn Research Center s Advanced Noise Control Fan was used as a test bed. A duct wall-mounted phased array consisting of several rings of microphones was employed. The data are mathematically resampled in the fan rotating reference frame and subsequently used in a conventional beamforming technique. The steering vectors for the beamforming technique are derived from annular duct modes, so that effects of reflections from the duct walls are reduced.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216800 , AIAA Paper 2010-3800 , E-17431 , 16th Aeroacoustics Conference; Jun 07, 2010 - Jun 09, 2010; Stockholm; Sweden
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 89
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    Effect of Turbulence Modeling on an Excited Jet (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The flow dynamics in a high-speed jet are dominated by unsteady turbulent flow structures in the plume. Jet excitation seeks to control these flow structures through the natural instabilities present in the initial shear layer of the jet. Understanding and optimizing the excitation input, for jet noise reduction or plume mixing enhancement, requires many trials that may be done experimentally or computationally at a significant cost savings. Numerical simulations, which model various parts of the unsteady dynamics to reduce the computational expense of the simulation, must adequately capture the unsteady flow dynamics in the excited jet for the results are to be used. Four CFD methods are considered for use in an excited jet problem, including two turbulence models with an Unsteady Reynolds Averaged Navier-Stokes (URANS) solver, one Large Eddy Simulation (LES) solver, and one URANS/LES hybrid method. Each method is used to simulate a simplified excited jet and the results are evaluated based on the flow data, computation time, and numerical stability. The knowledge gained about the effect of turbulence modeling and CFD methods from these basic simulations will guide and assist future three-dimensional (3-D) simulations that will be used to understand and optimize a realistic excited jet for a particular application.
    Schlagwort(e): Acoustics
    Materialart: NASA/TM-2010-216768 , AIAA Paper 2009-3191 , E-17393 , 15th Aeroacoustics Conference (30th AIAA Aeroacoustics Conference); May 11, 2009 - May 13, 2009; Miami, FL; United States
    Format: application/pdf
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