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  • 1
    Publication Date: 2017-10-02
    Description: The flowfield induced by a single, subsonic jet exhausting perpendicularly from a flat plate into a subsonic crossflow has been numerically investigated. The test case was chosen to match available experimental data where the jet Mach number was 0.78, and the freestream Mach number was 0.13. Time-averaged solutions were obtained using the thin-layer Navier-Stokes equations and two overlapping grids. The solutions were sensitive to the radial grid clustering near the edge of the jet and to the far-field boundary conditions. Experimental data comparisons were required to determine the most appropriate jet grid and satisfactory boundary conditions. Globally, the solutions converged in about 6000 iterations. The computational results accurately showed the deflected jet and associated contrarotating vortices. The fine clustered grid in the region upstream of the jet exit allowed the horseshoe vortex in the boundary layer near the jet exit to be captured. Most importantly for aircraft applications, the computed plate pressure distributions compared favorably with the experimental data over most of the surface. However, in the wake region immediately downstream of the jet exit, where there is extensive flow separation, some discrepancies with experimental data were observed. Two turbulence models were used in this study: (1) the zero-equation, two layer Baldwin-Lomax turbulence model; and (2) one-equation Baldwin-Barth turbulence model. The turbulence models gave results which generally compared no better with experimental data than the laminar computation results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AGARD, Computational and Experimental Assessment of Jets in Cross Flow; 14 p
    Format: text
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  • 2
    Publication Date: 2019-06-28
    Description: An investigation of the wing upper surface flow-field disturbance due to in-flight inboard thrust reverser deployment on the NASA DC-8-72, which was conducted cooperatively by NASA Ames, the Federal Aviation Administration (FAA), McDonnell Douglas, and the Aerospace Industry Association (AIA), is outlined and discussed in detail. The purpose of this flight test was to obtain tufted flow visualization data which demonstrates the effect of thrust reverser deployment on the wing upper surface flow field to determine if the disturbed flow regions could be modeled by computational methods. A total of six symmetric thrust reversals of the two inboard engines were performed to monitor tuft and flow cone patterns as well as the character of their movement at the nominal Mach numbers of 0.55, 0.70, and 0.85. The tufts and flow cones were photographed and video-taped to determine the type of flow field that occurs with and without the thrust reversers deployed. In addition, the normal NASA DC-8 onboard Data Acquisition Distribution System (DADS) was used to synchronize the cameras. Results of this flight test will be presented in two parts. First, three distinct flow patterns associated with the above Mach numbers were sketched from the motion videos and discussed in detail. Second, other relevant aircraft parameters, such as aircraft's angular orientation, altitude, Mach number, and vertical descent, are discussed. The flight test participants' comments were recorded on the videos and the interested reader is referred to the video supplement section of this report for that information.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TM-110351 , A-950060 , NAS 1.15:110351
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: A flow visualization study of several configurations of a jet-powered vertical takeoff and landing (VTOL) aircraft model during hover in ground effect was conducted. A surface oil flow technique was used to observe the flow patterns on the lower surfaces of the model. There were significant configuration effects. Wing height with respect to fuselage, the presence of an engine inlet duct beside the fuselage, and nozzle pressure ratio are seen to have strong effects on the surface flow angles on the lower surface of the wing. This test was part of a program to improve the methods for predicting the hot gas ingestion (HGI) for jet-powered vertical/short takeoff and landing (V/STOL) aircraft. The tests were performed at the Jet Calibration and Hover Test (JCAHT) Facility at Ames Research Center.
    Keywords: AERODYNAMICS
    Type: NASA-TM-108860 , A-95025 , NAS 1.15:108860
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  • 4
    Publication Date: 2019-07-13
    Description: The flowfield induced by a single, subsonic jet exhausting perpendicularly from a flat plate into a subsonic crossflow has been numerically investigated. Time-averaged solutions were obtained using the thin-layer Navier-Stokes equations and two overlapping grids. Test cases were chosen to match available experimental data where the jet Mach number was 0.78 and the freestream Mach number was varied to represent effective velocity ratios R from 4 to 12. Comparisons of the pressures induced on the flat plate are presented. The results show that the best agreement is obtained for R of 4 and 6, R of 8 is more difficult to resolve, and the R of 12 solution was not satisfactory. It is anticipated that the resolution could be improved by using either smaller time steps or finer grid spacing as R increases.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-4860 , ; 12 p.|Dec 01, 1993 - Dec 03, 1993; Santa Clara, CA; United States
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  • 5
    Publication Date: 2019-07-18
    Description: One concept for high lift aerodynamics is the trapped-vortex. Recently it has been suggested that several spoilers located at different chordwise locations on an airfoil could be deployed to form several cavities in the chordwise direction. This may provide a means of increasing upper surface camber and thereby increase wing lift. It is envisioned that the cavities would be located on an airfoil in its pressure recovery region. Investigations of the effect of one or more cavities on the adjacent boundary layer in an adverse boundary layer were not found in a literature survey. Since flow separation can be caused by flow over cavities, boundary layer measurements were made in the vicinity of cavities which were located in an adverse pressure gradient to study the associated flow in an effort to identify any benefits. The experimental data from the present investigation indicate a minimal impact on the boundary layer profiles is caused by the presence of cavities in either a constant pressure freestream or an adverse pressure gradient. The data from the experimental investigation has been obtained and analyzed. The computational investigation using an incompressible Navier-Stokes code show that reasonable results are being obtained when they are compared with the experimental data.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 34th Aerospace Sciences Meeting and Exhibit; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
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  • 6
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    In:  CASI
    Publication Date: 2019-07-13
    Description: The purpose of this workshop was to discuss the current understanding of the ground vortex phenomena and their effects on aircraft, and to establish directions for further research on advanced, high-performance aircraft designs, particularly those concepts utilizing powered-lift systems; e.g., V/STOL. ASTOVL, and STOL aircraft.
    Keywords: AERODYNAMICS
    Type: NASA-CP-10008 , A-88008 , NAS 1.55:10008 , Apr 22, 1987 - Apr 23, 1987; Moffett Field, CA; United States
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  • 7
    Publication Date: 2019-07-13
    Description: A numerical analysis is presented of the flowfield induced by a single subsonic jet exhausting perpendicularly from a flat plate into a subsonic crossflow. The analysis used available experimental data from a test case where the jet Mach number was 0.78 and the freestream Mach number was 0.13. Time-averaged solutions were obtained using the thin-layer Navier-Stokes equations and two overlapping grids. The effect of turbulence model on the solutions was evaluated using two turbulence models: the zero-equation two-layer Baldwin-Lomax (1978) turbulence model and the one-equation Baldwin-Barth (1990) turbulence model. It was found that, for some conditions, the zero-equation Baldwin-Lomax turbulence model gave better results than the one-equation Baldwin-Barth model or the laminar case.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-0870 , ; 21 p.|AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States
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