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  • 1
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    Laser Doppler Velocimeter measurements in a 3-D impinging twin-jet fountain flow (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Mean velocity and turbulence measurements were conducted on the three dimensional fountain flow field generated by the impingement of two axisymmetric jets on a ground plane with application to vertical takeoff and landing (VTOL) aircraft. The basic instantaneous velocity data were obtained using a two component laser Doppler velocimeter in a plane connecting the nozzle centerlines at different heights above the ground emphasizing the jet impingement region and the fountain upwash region formed by the collision of the wall jets. The distribution of mean velocity components and turbulence quantities, including the turbulence intensity and the Reynolds shear stress, were derived from the basic velocity data. Detailed studies of the characteristics of the fountain revealed self-similarity in the mean velocity and turbulence profiles across the fountain. The spread and mean velocity decay characteristics of the fountain were established. Turbulence intensities of the order of 50% were observed in the fountain.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Research Center Proceedings of the 1985 NASA Ames Research Center's Ground-Effects Workship; p 147-159
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Flow visualization studies of the internal flow characteristics in a simulated mixed flow vectored thrust ASTOVL engine configuration (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The characteristics of internal flowfields in a Mixed Flow Vectored Thrust (MFVT) propulsion system for Short Take Off and Vertical Landing (STOVL) fighter aircraft were investigated using flow visualization techniques. A highly parametric 14 percent scale transparent model was used to simulate the MFVT propulsion system. The working medium was water. The mixing between the fan and core flow was studied using flow visualization for a variety of geometrical and flow parameters including three bypass ratio variations. The flow visualization technique involves the use of laser light sheet for illumination and fluorescent dye or air bubbles as tracers. Results indicate the existence of a strong vortex flowfield in the hover mode of operation that is responsible for good mixing between the fan and core flows.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-1689
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Investigation of blown boundary layers with an improved wall jet system (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The behavior of two dimensional incompressible turbulent wall jets submerged in a boundary layer when they are used to prevent boundary layer separation on plane surfaces is investigated. The experimental set-up and instrumentation are described. Experimental results of zero pressure gradient flow and adverse pressure gradient flow are presented. Conclusions are given and discussed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-162512
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Measurements of a zero-pressure-gradient boundary layer blown by an asymmetric jet (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Measurements were made in a two-dimensional wall jet submerged under a thick upstream boundary layer and advancing into a zero-pressure-gradient flow with the ratios of jet velocity to the freestream velocity confined to a practical range (less than 2). The effect on the flow development of an asymmetric wall-jet velocity profile with a relatively higher concentration of momentum away from the wall was investigated. The flow was computed using an existing method for blown boundary layers, and the results show good agreement with experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 490
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Unsteady features of jets in lift and cruise modes for VTOL aircraft (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Experiments were performed to simulate jet plume effects associated with VTOL aircraft in takeoff and cruise modes. A water facility was used to investigate the influence of inclination angle and separation distance on the three-dimensional fountain flowfield generated by two impinging jets operating at a jet Reynolds number of 250,000. Substantial differences in the flow features were observed for different spacings between the jets. Plume effects in cruise mode were simulated by a supersonic unheated jet parallel to a wall. Variation of the distance between the wall and the edge of the plume is shown to have a major controlling effect on the supersonic screech instability.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 872359 , International Powered Lift Conference and Exposition; Dec 07, 1987 - Dec 10, 1987; Santa Clara, CA; United States
    Format: text
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  • 6
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    A summary of jet-impingement studies at McDonnell Douglas Research Laboratories (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: It has been the primary objective of the considered studies to determine and describe, through calculation, measurement, and visualization of the flowfields, the basic character of isolated and interacting impinging jets. The secondary objective has been to provide computed and experimental flow properties which can be used in the development and verification of empirically based prediction methodologies for complete aircraft configurations. The studies have resulted in the solution of the Reynolds-averaged Navier-Stokes and Jones-Launder turbulence model equations for two- and three-dimensional configurations and in the acquisition of an extensive data base and flow-visualization photographs for these configurations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2613 , V/STOL Conference; Dec 07, 1981 - Dec 09, 1981; Palo Alto, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Investigation of blown boundary layers with an improved wall jet system (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Measurements were made in a two dimensional incompressible wall jet submerged under a thick upstream boundary layer with a zero pressure gradient and an adverse pressure gradient. The measurements included mean velocity and Reynolds stresses profiles, skin friction, and turbulence spectra. The measurements were confined to practical ratios (less than 2) of the jet velocity to the free stream velocity. The wall jet used in the experiments had an asymmetric velocity profile with a relatively higher concentration of momentum away from the wall. An asymmetric jet velocity profile has distinct advantages over a uniform jet velocity profile, especially in the control of separation. Predictions were made using Irwin's (1974) method for blown boundary layers. The predictions clearly show the difference in flow development between an asymmetric jet velocity profile and a uniform jet velocity profile.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-3340
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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