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  • AERODYNAMICS  (15)
  • 2020-2021
  • 2005-2009
  • 1990-1994  (6)
  • 1985-1989  (9)
  • 1950-1954
  • 1
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    Effects of thrust reversing in ground proximity (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The changes in stability and control characteristics encountered by a thrust reversing aircraft during its final approach, landing, and ground roll are described. These changes include a strong pitch-up accompanied by the loss of horizontal tail and aileron control effectiveness. The magnitude of reverser induced changes in ground effect are much larger than corresponding changes in free air. Some unexpected unsteady motions exhibited in wind tunnel by an aircraft model with reversers operating in ground proximity are also described. The cause of this oscillatory behavior was determined to be an unsteady interaction between the wall jets formed by impingement of reverser jets on the ground and the on-coming free stream. Time histories of rolling moments measured by the wind tunnel balance or support system were removed and frequencies were scaled by Strouhal number to full scale. Corrected time series were used to simulate the motion of a fighter aircraft with thrust reversers in ground effect. The simulation predicted large roll angles and nose down attitude at touchdown. Some phenomena of jet attachment to solid surfaces are discussed and areas for future research are recommended.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center Proceedings of the 1985 NASA Ames Research Center's Ground-Effects Workshop; p 239-288
    Format: application/pdf
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  • 2
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    A Petrov-Galerkin finite element method for the compressible Euler and Navier-Stokes equations (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An overview of a new finite element method for the compressible Euler and Navier-Stokes equations is presented. The discretization is based on entropy variables. The method is developed within the framework of a Petrov-Galerkin formulation. Two perturbations are added to the weighting function; one is a generalization of the SUPG operator and the other is designed to enhance shock capturing capability. The treatment of boundary conditions and the consistent calculation of boundary fluxes are addressed. Results of numerical tests are presented which confirm the robustness and wide applicability of the method.
    Keywords: AERODYNAMICS
    Format: text
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  • 3
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    Application of the Galerkin/least-squares formulation to the analysis of hypersonic flows. I - Flow over a two-dimensional ramp (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An FEM for the compressible Navier-Stokes equations is introduced. The discretization is based on entropy variables. The methodology is developed within the framework of a Galerkin/least-squares formulation to which a discontinuity-capturing operator is added. Results for three test cases selected among those of the Workshop on Hypersonic Flows for Reentry Problems are presented.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 181-200.
    Format: text
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  • 4
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    Application of the Galerkin/least-squares formulation to the analysis of hypersonic flows. II - Flow past a double ellipse (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A finite element method for the compressible Navier-Stokes equations is introduced. The discretization is based on entropy variables. The methodology is developed within the framework of a Galerkin/least-squares formulation to which a discontinuity-capturing operator is added. Results for four test cases selected among those of the Workshop on Hypersonic Flows for Reentry Problems are presented.
    Keywords: AERODYNAMICS
    Type: In: Hypersonic flows for reentry problems. Vol. 2 (A93-42576 17-02); p. 427-450.
    Format: text
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  • 5
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    Summary of low-speed wind tunnel results of several high-speed counterrotation propeller configurations (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The low speed aerodynamic performance characteristics of several advanced counterrotation pusher propeller configurations with cruise design Mach numbers of 0.72 and 0.80 were investigated in the NASA Low Speed Wind Tunnel. The tests were conducted at Mach numbers representative of the takeoff and landing flight regime. The investigation included: (1) the propeller performance characteristics over a range of blade angle settings and rotational speeds at a Mach number of 0.20; (2) the effect on the propeller performance of varying the axial rotor spacing and mismatching the power and rotational speeds on the propeller rotors; and (3) determining the reverse thrust performance characteristics at Mach numbers of 0.0, 0.10, 0.15 and 0.20. The results of the investigation indicated that the overall low speed performance of the counterrotation propeller configurations was reasonable.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-3149
    Format: text
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  • 6
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    Summary of low-speed wind tunnel results of several high-speed counterrotation propeller configurations (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The low speed aerodynamic performance characteristics of several advanced counterrotation pusher propeller configurations with cruise design Mach numbers of 0.72 and 0.80 were investigated in the NASA Low Speed Wind Tunnel. The tests were conducted at Mach numbers representative of the takeoff and landing flight regime. The investigation included: (1) the propeller performance characteristics over a range of blade angle settings and rotational speeds at a Mach number of 0.20; (2) the effect on the propeller performance of varying the axial rotor spacing and mismatching the power and rotational speeds on the propeller rotors; (3) determining the reverse thrust performance characteristics at Mach numbers of 0.0, 0.10, 0.15 and 0.20. The results of the investigation indicated that the overall low speed performance of the counterrotation propeller configurations was reasonable.
    Keywords: AERODYNAMICS
    Type: NASA-TM-100945 , E-4234 , NAS 1.15:100945 , AIAA PAPER 88-3149
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  • 7
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    Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take/off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller mode to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-2583
    Format: text
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  • 8
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    Analytical modeling of circuit aerodynamics in the new NASA Lewis Altitude Wind Tunnel (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modelling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modelling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0380
    Format: text
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  • 9
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    Flow analysis for the nacelle of an advanced ducted propeller at high angle-of-attack and at cruise with boundary layer control (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An axisymmetric panel code and a three dimensional Navier-Stokes code (used as an inviscid Euler code) were verified for low speed, high angle of attack flow conditions. A three dimensional Navier-Stokes code (used as an inviscid code), and an axisymmetric Navier-Stokes code (used as both viscous and inviscid code) were also assessed for high Mach number cruise conditions. The boundary layer calculations were made by using the results from the panel code or Euler calculation. The panel method can predict the internal surface pressure distributions very well if no shock exists. However, only Euler and Navier-Stokes calculations can provide a good prediction of the surface static pressure distribution including the pressure rise across the shock. Because of the high CPU time required for a three dimensional Navier-Stokes calculation, only the axisymmetric Navier-Stokes calculation was considered at cruise conditions. The use of suction and tangential blowing boundary layer control to eliminate the flow separation on the internal surface was demonstrated for low free stream Mach number and high angle of attack cases. The calculation also shows that transition from laminar flow to turbulent flow on the external cowl surface can be delayed by using suction boundary layer control at cruise flow conditions. The results were compared with experimental data where possible.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106371 , AIAA PAPER 94-0391 , E-8181 , NAS 1.15:106371 , Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 10
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    Further development and flight test of an autonomous precision landing system using a parafoil (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA Dryden Flight Research Center and NASA Johnson Space Center are jointly conducting a phased program to determine the feasibility of the autonomous recovery of a spacecraft using a ram-air parafoil system for the final stages of entry from space to a precision landing. The feasibility is being studied using a flight model of a spacecraft in the generic shape of a flattened biconic that weighs approximately 120 lb and is flown under a commercially available ram-air parafoil. Key components of the vehicle include the global positioning system (GPS) guidance for navigation, a flight control computer, an electronic compass, a yaw rate gyro, and an onboard data recorder. A flight test program is being used to develop and refine the vehicle. The primary flight goal is to demonstrate autonomous flight from an altitude of 3,000 m (10,000 ft) with a lateral offset of 1.6 km (1.0 mi) to a precision soft landing. This paper summarizes the progress to date. Much of the navigation system has been tested, including a heading tracker that was developed using parameter estimation techniques and a complementary filter. The autoland portion of the autopilot is still in development. The feasibility of conducting the flare maneuver without servoactuators was investigated as a means of significantly reducing the servoactuator rate and load requirements.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4599 , H-1987 , NAS 1.15:4599 , AIAA PAPER 94-2141 , Biennial Flight Test Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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