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  • 11
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    On the stability of swept wing laminar boundary layers including curvature effects (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A linear stability analysis that encompasses curvature effects has been conducted in wind tunnel experiments on a swept NACA 64(2)-A015 wing, and published transition-onset results have been correlated with computed N-factor values. A strong stabilizing influence is noted upon the growth of the crossflow disturbance, when the flow is accelerated in regions of high body curvature. The maximum amplified crossflow disturbances were in all cases travelling waves; when TS waves reached their maximum, the N-factors at transition lay in the 9.9-13.8 range. Stabilization due to curvature effects was less pronounced in cases where acceleration occurred over a large portion of chord.
    Keywords: AERODYNAMICS
    Type: IUTAM Symposium on Laminar-Turbulent Transition; Sept. 11-15, 1989; Toulouse; France
    Format: text
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    NASA TECHNICAL REPORTS
  • 12
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    Correlation of boundary layer stability analysis with flight transition data (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Recently, NASA completed a boundary-layer transition flight test on an F-14 aircraft which has variable-sweep capability. Transition data were acquired for a wide variety of sweep angles, pressure distributions, Mach numbers, and Reynolds numbers. In this paper, the F-14 flight test is briefly described and N-factor correlations with measured transition locations are presented for one of two gloves flown on the F-14 wing in the flight program; a thin foam and fiberglass glove which provided a smooth sailplane finish on the basic F-14, modified NACA 6-series airfoil. For these correlations, an improved linear boundary-layer stability theory was utilized that accounts for compressibility and surface and streamline curvature effects for the flow past swept wings.
    Keywords: AERODYNAMICS
    Type: IUTAM Symposium on Laminar-Turbulent Transition; Sept. 11-15, 1989; Toulouse; France
    Format: text
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    NASA TECHNICAL REPORTS
  • 13
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    Prediction of forces and moments for flight vehicle control effectors. Part 1: Validation of methods for predicting hypersonic vehicle controls forces and moments (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Many types of hypersonic aircraft configurations are currently being studied for feasibility of future development. Since the control of the hypersonic configurations throughout the speed range has a major impact on acceptable designs, it must be considered in the conceptual design stage. The ability of the aerodynamic analysis methods contained in an industry standard conceptual design system, APAS II, to estimate the forces and moments generated through control surface deflections from low subsonic to high hypersonic speeds is considered. Predicted control forces and moments generated by various control effectors are compared with previously published wind tunnel and flight test data for three configurations: the North American X-15, the Space Shuttle Orbiter, and a hypersonic research airplane concept. Qualitative summaries of the results are given for each longitudinal force and moment and each control derivative in the various speed ranges. Results show that all predictions of longitudinal stability and control derivatives are acceptable for use at the conceptual design stage. Results for most lateral/directional control derivatives are acceptable for conceptual design purposes; however, predictions at supersonic Mach numbers for the change in yawing moment due to aileron deflection and the change in rolling moment due to rudder deflection are found to be unacceptable. Including shielding effects in the analysis is shown to have little effect on lift and pitching moment predictions while improving drag predictions.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186571 , NAS 1.26:186571
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 14
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    Euler and Potential Experiment/CFD Correlations for a Transport and Two Delta-Wing Configurations (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A selection of successes and failures of Computational Fluid Dynamics (CFD) is discussed. Experiment/CFD correlations involving full potential and Euler computations of the aerodynamic characteristics of four commercial transport wings and two low aspect ratio, delta wing configurations are shown. The examples consist of experiment/CFD comparisons for aerodynamic forces, moments, and pressures. Navier-Stokes equations are not considered.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102208 , A-89197 , NAS 1.15:102208
    Format: application/pdf
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  • 15
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    Prediction of forces and moments for flight vehicle control effectors. Part 2: An analysis of delta wing aerodynamic control effectiveness in ground effect (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Many types of hypersonic aircraft configurations are currently being studied for feasibility of future development. Since the control of the hypersonic configurations throughout the speed range has a major impact on acceptable designs, it must be considered in the conceptual design stage. Here, an investigation of the aerodynamic control effectiveness of highly swept delta planforms operating in ground effect is presented. A vortex-lattice computer program incorporating a free wake is developed as a tool to calculate aerodynamic stability and control derivatives. Data generated using this program are compared to experimental data and to data from other vortex-lattice programs. Results show that an elevon deflection produces greater increments in C sub L and C sub M in ground effect than the same deflection produces out of ground effect and that the free wake is indeed necessary for good predictions near the ground.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186572 , NAS 1.26:186572
    Format: application/pdf
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  • 16
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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
    Format: application/pdf
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  • 17
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    Computation of crossing shock/turbulent boundary layer interaction at Mach 8.3 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A three-dimensional (3D) hypersonic crossing shock wave/turbulent boundary-layer interaction is examined numerically at Mach 8.3. The test geometry consists of a pair of opposing sharp fins of angle alpha = 15 deg, mounted on a flat plate. Two theoretical models are evaluated. The full (3D) Reynolds-averaged Navier-Stokes equations are solved using the Baldwin-Lomax and the Rodi (modified k-epsilon) turbulence models. Computed results for both cases show good agreement with experiment for flat plate surface pressure and for flowfield profiles of pitot pressure and yaw angle, indicating that the flowfield is primarily rotational and inviscid. Fair to poor agreement is obtained for surface heat transfer, indicating a need for more accurate turbulence models. The overall flowfield structure is similar to that observed in previous crossing shock interaction studies.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 31; 8; p. 1369-1376.
    Format: text
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  • 18
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    Effect of a rotating propeller on the separation angle of attack and distortion in ducted propeller inlets (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The present study represents an extension of an earlier wind tunnel experiment performed with the P&W 17-in. Advanced Ducted Propeller (ADP) Simulator operating at Mach 0.2. In order to study the effects of a rotating propeller on the inlet flow, data were obtained in the UTRC 10- by 15-Foot Large Subsonic Wind Tunnel with the same hardware and instrumentation, but with the propeller removed. These new tests were performed over a range of flow rates which duplicated flow rates in the powered simulator program. The flow through the inlet was provided by a remotely located vacuum source. A comparison of the results of this flow-through study with the previous data from the powered simulator indicated that in the conventional inlet the propeller produced an increase in the separation angle of attack between 4.0 deg at a specific flow of 22.4 lb/sec-sq ft to 2.7 deg at a higher specific flow of 33.8 lb/sec-sq ft. A similar effect on separation angle of attack was obtained by using stationary blockage rather than a propeller.
    Keywords: AERODYNAMICS
    Type: NASA-TM-105935 , E-7451 , NAS 1.15:105935 , AIAA PAPER 93-0017 , Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States
    Format: application/pdf
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  • 19
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    Evaluation of panel code predictions with experimental results of inlet performance for a 17-inch ducted prop/fab simulator operating at Mach 0.2 (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An axisymmetric panel code was used to evaluate a series of ducted propeller inlets. The inlets were tested in the Lewis 9 by 15 Foot Low Speed Wind Tunnel. Three basic inlets having ratios of shroud length to propeller diameter of 0.2, 0.4, and 0.5 were tested with the Pratt and Whitney ducted prop/fan simulator. A fourth hybrid inlet consisting of the shroud from the shortest basic inlet coupled with the spinner from the largest basic inlet was also tested. This later configuration represented the shortest overall inlet. The simulator duct diameter at the propeller face was 17.25 inches. The short and long spinners provided hub-to-tip ratios of 0.44 at the propeller face. The four inlets were tested at a nominal free stream Mach number of 0.2 and at angles of attack from 0 degrees to 35 degrees. The panel code method incorporated a simple two-part separation model which yielded conservative estimates of inlet separation.
    Keywords: AERODYNAMICS
    Type: NASA-TM-104428 , E-6261 , NAS 1.15:104428 , AIAA PAPER 91-3354 , Joint Propulsion Conference; Jun 24, 1991 - Jun 27, 1991; Sacramento, CA; United States
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  • 20
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    Numerical simulation of crossing/turbulent boundary layer interaction at Mach 8.3 comparison of zero and two-equation turbulence models (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A 3D hypersonic crossing shock wave/turbulent boundary layer interaction is examined numerically. The test geometry consists of a pair of opposing sharp fins of angle alpha = 15 deg mounted on a flat plate. The freestream Mach number is 8.28. Two theoretical models are evaluated. The full 3D Reynolds-averaged Navier-Stokes equations are solved using the Baldwin-Lomax algebraic turbulent eddy viscosity model and the Rodi turbulence model. Computed results for both cases show good agreement with experiment for flat plate surface pressure and for pitot pressure and yaw angle profiles in the flowfield. General agreement is obtained for surface flow direction. Fair to poor agreement is obtained for surface heat transfer, indicating a need for more accurate turbulence models. The overall flowfield structure is similar to that observed in previous crossing shock interaction studies.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-0779 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 19 p.
    Format: text
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