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  • 1
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    An Introductory Review to Surface Reconstruction (2020)
    Institute of Physics
    Details
    Publication Date: 2020-07-10
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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    PAPER CURRENT
  • 2
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    An alternative Candida spp. cell wall disruption method using a basic sorbitol lysis buffer and glass beads (2008)
    Elsevier
    Details
    Publication Date: 2008-12-01
    Print ISSN: 0167-7012
    Electronic ISSN: 1872-8359
    Topics: Biology
    Published by Elsevier
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  • 3
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    Unsteady aerodynamic behavior of an airfoil with and without a slat (1993)
    Elsevier
    Details
    Publication Date: 1993-07-01
    Print ISSN: 0045-7930
    Electronic ISSN: 1879-0747
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Elsevier
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  • 4
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    Unsteady aerodynamic behavior of an airfoil with and without a slat (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Unsteady flow behavior and load characteristics of a 2D VR-7 airfoil with and without a leading-edge slat were studied in the water tunnel of the Aeroflightdynamics Directorate, NASA Ames Research Center. Both airfoils were oscillated sinusoidally between 5 and 25 deg at Re = 200,000 to obtain the unsteady lift, drag, and pitching moment data. A fluorescent dye was released from an orifice located at the leading edge of the airfoil for the purpose of visualizing the boundary layer and wake flow. The flowfield and load predictions of an incompressible Navier-Stokes code based on a velocity-vorticity formulation were compared with the test data. The test and predictions both confirm that the slatted VR-7 airfoil delays both static and dynamic stall as compared to the VR-7 airfoil alone.
    Keywords: AERODYNAMICS
    Type: Computers & Fluids (ISSN 0045-7930); 22; 4-5; p. 529-547.
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Effect of wake structure on blade-vortex interaction phenomena: Acoustic prediction and validation (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: During the Higher Harmonic Control Aeroacoustic Rotor Test, extensive measurements of the rotor aerodynamics, the far-field acoustics, the wake geometry, and the blade motion for powered, descent, flight conditions were made. These measurements have been used to validate and improve the prediction of blade-vortex interaction (BVI) noise. The improvements made to the BVI modeling after the evaluation of the test data are discussed. The effects of these improvements on the acoustic-pressure predictions are shown. These improvements include restructuring the wake, modifying the core size, incorporating the measured blade motion into the calculations, and attempting to improve the dynamic blade response. A comparison of four different implementations of the Ffowcs Williams and Hawkings equation is presented. A common set of aerodynamic input has been used for this comparison.
    Keywords: AERODYNAMICS
    Type: NASA-TM-110825 , NAS 1.15:110825 , AD-A294477
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    The effects of vortex modeling on blade-vortex interaction noise prediction (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The use of a blade vortex interaction noise prediction scheme, based on CAMRAD/JA, FPR and RAPP, quantifies the effects of errors and assumptions in the modeling of the helicopter's shed vortex on the acoustic predictions. CAMRAD/JA computes the wake geometry and inflow angles that are used in FPR to solve for the aerodynamic surface pressures. RAPP uses these surface pressures to predict the acoustic pressure. Both CAMRAD/JA and FPR utilize the Biot-Savart Law to determine the influence of the vortical velocities on the blade loading and both codes use an algebraic vortex model for the solid body rotation of the vortex core. Large changes in the specification of the vortex core size do not change the inplane wake geometry calculated by CAMRAD/JA and only slightly affect the out-of-plane wake geometry. However, the aerodynamic surface pressure calculated by FPR changes in both magnitude and character with small changes to the core size used by the FPR calculations. This in turn affects the acoustic predictions. Shifting the CAMRAD/JA wake geometry away from the rotor plane by 1/4 chord produces drastic changes in the acoustic predictions indicating that the prediction of acoustic pressure is extremely sensitive to the miss distance between the vortex and the blade and that this distance must be calculated as accurately as possible for acceptable noise predictions. The inclusion or exclusion of a vortex in the FPR-RAPP calculation allows for the determination of the relative importance of that vortex as a BVI noise source.
    Keywords: ACOUSTICS
    Type: NASA-TM-110823 , NAS 1.15:110823 , AD-A294466
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  • 7
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    Prediction and measurement of blade-vortex interaction loading (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An extensive quantity of airload measurements was obtained for a pressure-instrumented model of the BO-105 main rotor for a large number of higher-harmonic control (HHC) settings at Duits-Nederlandse Wind Tunnel (DNW). The wake geometry, vortex strength, and vortex core size were also measured through a laser light sheet technique and LDV. These results are used to verify the BVI airload prediction methodologies developed by AFDD, DLR, NASA Langley, and ONERA. The comparisons show that an accurate prediction of the blade motion and the wake geometry is the most important aspect of the BVI airload predictions.
    Keywords: AERODYNAMICS
    Type: NASA-TM-110824 , NAS 1.15:110824 , AD-A294468
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Characteristics of deformable leading edge for high performance helicopter rotor (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The deformable leading edge (DLE) concept to improve the blade capability in lift, drag and pitching moments has been investigated for the purpose of meeting new rotor maneuverability and susceptibility requirements. The advantages and disadvantages of this concept have been carefully examined with limited computational and experimental results. This work showed that this concept achieves a substantial improvement in lift capability and also reduces the drag and pitching moment at the same time. Effects of various parameters, such as Reynolds number, reduced frequency, mean angle of oscillation, and airfoil shape, on the performance of these airfoils were also investigated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-3526 , AD-A268648 , In: AIAA Applied Aerodynamics Conference, 11th, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 2 (A93-47201 19-02); p. 968-988.
    Format: text
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  • 9
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    Geometric analysis of wing sections (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes a new geometric analysis procedure for wing sections. This procedure is based on the normal mode analysis for continuous functions. A set of special shape functions is introduced to represent the geometry of the wing section. The generators of the NACA 4-digit airfoils were included in this set of shape functions. It is found that the supercritical wing section, Korn airfoil, could be well represented by a set of ten shape functions. Preliminary results showed that the number of parameters to define a wing section could be greatly reduced to about ten. Hence, the present research clearly advances the airfoil design technology by reducing the number of design variables.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-110346 , A-950049 , NAS 1.15:110346
    Format: application/pdf
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  • 10
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    Performance and Flowfield Measurements on a 10-inch Ducted Rotor VTOL UAV (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: A ducted fan VTOL UAV with a 10-inch diameter rotor was tested in the US Army 7-by 10-Foot Wind Tunnel. The test conditions covered a range of angle of attack from 0 to 110 degrees to the freestream. The tunnel velocity was varied from 0 (simulating a hover condition) to 128 ft/sec in propeller mode. A six-component internal balance measured the aerodynamic loads for a range of model configurations. including the isolated rotor, the isolated duct, and the full configuration of the duct and rotor. For some conditions, hotwire velocity surveys were conducted along the inner and outer surface of the duct and across the downstream wake. In addition, fluorescent oil flow visualization allowed the flow separation patterns inside and outside of the duct to be mapped for a few test conditions. Two different duct shapes were tested to determine the performance effects of leading edge radius. For each duct, a range of rotor tip gap from 1%R to 4.5%R was tested to determine the performance penalty in hover and axial flight. Measured results are presented in terms of hover performance, hover performance in a crosswind, and high angle of attack performance in propeller mode. In each case, the effects of both tip gap and duct leading edge radius are illustrated using measurements. Some of the hover performance issues were also studied using a simple analytical method, and the results agreed with the measurements.
    Keywords: Aircraft Design, Testing and Performance
    Format: application/pdf
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