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  • Aerodynamics
  • Age, comment; Age, dated; Age, dated standard error; Atlantic meridional overturning circulation; ATLAS; A Trans-Atlantic assessment and deep-water ecosystem-based spatial management plan for Europe; Calendar age; deep water formation; DEPTH, sediment/rock; Fraction modern carbon; Fraction modern carbon, error; Knorr; KNR178; KNR178-48JPC; PC; Piston corer; Sample code/label; Sample ID; sortable silt; subsurface ocean temperatures; Taxon/taxa
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  • 1
    Publication Date: 2011-08-23
    Description: Helicopter rotor aerodynamics is basically the study of unsteady aerodynamic flows in a rotating and translating coordinate system. Current trends in this field are briefly reviewed by examining recent advances in lifting-surface theory, wake modeling, panel methods, and finite-difference models' Examples are used to illustrate selected current methods and some indications of promising future directions are highlighted.
    Keywords: Aerodynamics
    Type: Vertica (ISSN 0360-5450); Volume 11; Nos. 1, 2; 43-63
    Format: text
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  • 2
    Publication Date: 2018-06-06
    Description: New ideas are forthcoming to break existing bottlenecks in using CFD during design. CAD-based automated grid generation. Multi-disciplinary use of embedded, overset grids to eliminate complex gridding problems. Use of time-averaged detached-eddy simulations as norm instead of "steady" RANS to include effects of self-excited unsteadiness. Combined GPU/Core parallel computing to provide over an order of magnitude increase in performance/price ratio. Gas-turbine applications are shown here but these ideas can be used for other Air Force, Navy, and NASA applications.
    Keywords: Aerodynamics
    Type: Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics; 43-60; NASA/CP-2010-216112
    Format: application/pdf
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  • 3
    Publication Date: 2019-07-19
    Description: The second flight of the HYPER-X Program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe integrated scramjet powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets, frequency sweeps, and pull-up/push-over maneuvers performed throughout the X-43A cowl-closed descent phase. The subject flight research maneuvers were conducted in a Mach number range of 6.8 to 0.95 at altitudes from 92,000 ft to sea level. In this flight regime, the dynamic pressure varied from 1300 psf to 400 psf with angle-of-attack ranging from 0 deg to 14 deg. The flight-extracted aerodynamics were compared with pre-flight predictions based on wind tunnel test data. The X-43A flight-derived axial force was found to be 10 to 15 percent higher than prediction. Under-predictions of similar magnitude were observed for the normal force. For Mach numbers greater than 4, the X-43A flight-derived stability and control characteristics resulted in larger than predicted static margins, with the largest discrepancy approximately 5-inches forward along the X(CG) at Mach 6. This would result in less static margin in pitch. The X-43A predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle-of-sideslip.
    Keywords: Aerodynamics
    Type: DFRC-459
    Format: text
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  • 4
    Publication Date: 2019-07-18
    Description: Ongoing research has shown that compressible dynamic stall can be caused by vastly different mechanisms even for small changes in flow conditions. For example, at low Mach numbers (M less than 0.3) and Reynolds numbers (less than 1 x 10(exp 6)), the bursting of the laminar separation bubble induces dynamic stall. At a slightly higher Mach number (M = 0.45) and around the same Reynolds number, shock induced separation can cause dynamic stall. Also, the mechanism changes from that of laminar separation bubble bursting to that due to excessive adverse pressure gradient, with increase of Reynolds number. Complex interactions occurring between the local supersonic flow and the bubble lead to another possible mechanism of dynamic stall. Since all these mechanisms may be encountered by a rotor-blade during a single cycle, there is a strong need to devise a reliable flow control method for use under such dramatically varying conditions. Whereas it is a Ali 'Beneficent challenge, identification of the fact that these mechanisms are all in some way related to the airfoil leading edge adverse pressure gradient, has resulted in an effective method of flow control to be described.
    Keywords: Aerodynamics
    Type: IUTAM Symposium on Mechanics of Passive and Active Flow Control; Sep 07, 1998 - Sep 11, 1998; Goettingen; Germany
    Format: text
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  • 5
    Publication Date: 2019-07-18
    Description: The interaction of an external disturbance with a laminar boundary layer over a flat plate with distributed roughness is investigated using combined experimental and numerical methods. The experiment is modeled with an unsteady boundary layer code using second order backward differencing. The simulation includes the second order scattering from roughness elements at and near the first streamwise station of predicted boundary layer instability. A comparison of experimental measurements of the boundary layer perturbation due to the wake from a vibrating ribbon with the computed first order forced boundary layer perturbation showed excellent agreement. Second order roughness induced eigenfunctions from boundary layer theory are examined and compared with other forms of excitation
    Keywords: Aerodynamics
    Type: 49th Annual Meeting; Nov 24, 1996 - Nov 26, 1996; Syracuse, NY; United States
    Format: text
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  • 6
    Publication Date: 2019-07-13
    Description: An overview of aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign test vehicle is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a helium balloon, then accelerating the TV to Mach 4 and 53 km altitude with a solid rocket motor. Test flights conducted in June of 2014 (SFDT-1) and 2015 (SFDT-2) each successfully delivered a 6 meter diameter decelerator (SIAD-R) to test conditions and several seconds of flight, and were successful in demonstrating the SFDT flight system concept and SIAD-R technology. Aerodynamic models and uncertainties developed for the SFDT campaign are presented, including the methods used to generate them and their implementation within an aerodynamic database (ADB) routine for flight simulations. Pre- and post-flight aerodynamic models are compared against reconstructed flight data and model changes based upon knowledge gained from the flights are discussed. The pre-flight powered phase model is shown to have a significant contribution to off-nominal SFDT trajectory lofting, while coast and SIAD phase models behaved much as predicted.
    Keywords: Aerodynamics
    Type: NF1676L-22595 , 2016 AIAA Aviation Conference; Jun 13, 2016 - Jun 17, 2016; Washington, DC; United States
    Format: application/pdf
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  • 7
    Publication Date: 2019-07-13
    Description: Phase II data results of the Fundamental Inlet Bleed Experiments study at NASA Glenn Research Center are presented which include flow coefficient behavior for 21 bleed hole configurations. The bleed configurations are all round holes with hole diameters ranging from 0.795 to 6.35 mm, hole inclination angles from 20deg to 90deg, and thickness-to-diameter ratios from 0.25 to 2.0. All configurations were tested at a unit Reynolds number of 2.46 10(exp 7)/m and at discrete local Mach numbers of 1.33, 1.62, 1.98, 2.46, and 2.92. Interactions between the design parameters of hole diameter, hole inclination angle, and thickness-to-diameter as well as the interactions between the flow parameters of pressure ratio and Mach number upon the flow coefficient are examined, and a preliminary statistical model is proposed. An existing correlation is also examined with respect to this data.
    Keywords: Aerodynamics
    Type: NASA/TM-2013-217843 , E-18617 , AIAA Paper 2013-0424 , 51st Aerospace Science Conference; Jan 07, 2013 - Jan 10, 2013; Grapevine, TX; United States
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  • 8
    Publication Date: 2019-10-04
    Description: NASAs Advanced Air Transport Technology (AATT) project is investigating boundary layer ingesting (BLI) propulsors for advanced subsonic commercial vehicle concepts to enable the reduction of fuel burn. A multidisciplinary team of researchers from NASA, United Technologies Research Center (UTRC), Virginia Polytechnic University, and the Air Force Arnold Engineering Development Complex developed and tested an embedded BLI inlet and distortion-tolerant fan (BLI2DTF) system in the NASA Glenn Research Center (GRC) 8- foot by 6-foot (8x6) transonic wind tunnel. The test demonstrated the component performance goals necessary for an overall fuel burn reduction of 3 to 5 percent on a large hybrid wing body (HWB) aircraft. Special test equipment, including a raised floor with flow effectors and a bleed system, was developed for use in the 8x6 to produce the appropriate incoming boundary layer representative of an HWB application. Detailed measurements were made to determine the inlet total pressure loss and distortion, fan stage efficiency, and aeromechanic performance including blade vibration stress and displacement response. Results from this test were used as input to a vehicle-level system study performed by the AATT project to assess the impact of BLI on an alternative advanced concept aircraft referred to as the NASA D8 (ND8), which is somewhat similar to the HWB in its integration of the propulsor. This paper will provide an overview of the project timeline, special test equipment needed in the wind tunnel to develop the appropriate incoming boundary layer, and the difficulties in designing a propulsor for the test. The paper will conclude with some representative aerodynamic and aeromechanic data from the test itself and conclude with how this data was used in the ND8 system study.
    Keywords: Aerodynamics
    Type: ISABE-2019-24264 , GRC-E-DAA-TN72111 , International Society for Air Breathing Engines (ISABE) Conference; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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  • 9
    Publication Date: 2019-10-29
    Description: _NASA's Advanced Air Transport Technology (AATT) project is investigating boundary layer ingesting (BLI) propulsors for advanced subsonic commercial vehicle concepts to enable the reduction of fuel burn. A multidisciplinary team of researchers from NASA, United Technologies Research Center (UTRC), Virginia Polytechnic University, and the Air Force Arnold Engineering Development Complex developed and tested an embedded BLI inlet and distortion-tolerant fan (BLI2DTF) system in the NASA Glenn Research Center (GRC) 8-foot by 6-foot (8x6) transonic wind tunnel. The test demonstrated the component performance goals necessary for an overall fuel burn reduction of 3 to 5 percent on a large hybrid wing body (HWB) aircraft. Special test equipment, including a raised floor with flow effectors and a bleed system, was developed for use in the 8x6 to produce the appropriate incoming boundary layer representative of an HWB application. Detailed measurements were made to determine the inlet total pressure loss and distortion, fan stage efficiency, and aeromechanic performance including blade vibration stress and displacement response. Results from this test were used as input to a vehicle-level system study performed by the AATT project to assess the impact of BLI on an alternative advanced concept aircraft referred to as the NASA D8 (ND8), which is somewhat similar to the HWB in its integration of the propulsor. This paper will provide an overview of the project timeline, special test equipment needed in the wind tunnel to develop the appropriate incoming boundary layer, and the difficulties in designing a propulsor for the test. The paper will conclude with some representative aerodynamic and aeromechanic data from the test itself and conclude with how this data was used in the ND8 system study.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN73213 , International Society for Air Breathing Engines (ISABE) Conference; Sep 22, 2019 - Sep 27, 2019; Canberra; Australia
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  • 10
    Publication Date: 2019-07-13
    Description: Phase I data results of the Fundamental Inlet Bleed Experiments project at NASA Glenn Research Center (GRC) are presented which include flow coefficient results for two single-hole boundary-layer bleed configurations. The bleed configurations tested are round holes at inclination angles of 90deg and 20deg both having length-to-diameter ratios of 2.0. Results were obtained at freestream Mach numbers of 1.33, 1.62, 1.98, 2.46, and 2.92 and unit Reynolds numbers of 0.984, 1.89, and 2.46 10(exp 7)/m. Approach boundary-layer data are presented for each flow condition and the flow coefficient results are compared to existing multi-hole data obtained under similar conditions. For the 90deg hole, the single and multi-hole distributions agree fairly well with the exception that under supercritical operation, the multi-hole data chokes at higher flow coefficient levels. This behavior is also observed for the 20deg hole but to a lesser extent. The 20deg hole also shows a markedly different characteristic at subcritical operation. Also presented are preliminary results of a Computational Fluid Dynamics (CFD) analysis of both configurations at the Mach 1.33 and a unit Reynolds number of 2.46 10(exp 7)/m. Comparison of the results shows the agreement to be very good.
    Keywords: Aerodynamics
    Type: NASA/TM-2012-217620 , E-18208 , AIAA Paper 2012-0272 , 50th Aerospace Sciences Meeting; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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