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  • 1
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    An Analysis of the Pressures, Forces and Moments Induced by the Ground Vortex Generated by a Single Impinging Jet (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: When a jet STOVL aircraft is in STOL operation the jets impinge on the ground and generate wall jets flowing radially outward from the points at which the jets impinge. When the forward flowing part of a wall jet meets the free stream flow it is rolled back on itself forming a parabolic shaped ground vortex. Positive pressures are induced on the lower surface of the configuration ahead of the ground vortex and suction pressures are induced over the ground vortex itself. In addition, the suction pressures induced aft of the jet out of ground effect are reduced and lifting pressures are induced on the upper surface. This study analyzes available pressure and force data and develops a method for estimating the forces and moments induced in ground effect. The method includes the effects of configuration variables, height and operating conditions, as well as the effects of the location, deflection and shape of the jet. However, it is limited to single jets at subcritical nozzle pressure ratios. An analysis of the effects of moving over the ground vs. tests over a fixed ground plane is included.
    Keywords: Aerodynamics
    Type: NASA-CR-4765 , NAS 1.26:4765 , A-975988
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    The Effects of Crossflow on the Pressures and Lift Induced by the Fountain Generated Between Two Impinging Jets (1998)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: When a jet STOVL aircraft is hovering, or in a crossflow, while close to the ground wall jets flowing radially outward from the impingement points of the jets are generated. An upflow, or fountain, is generated where the wall jets from adjacent jets meet on the ground surface. The induced lift and suckdown generated by the impingement of the fountain on the lower surface of the configuration has been the subject of previous studies. This study analyzes the limited available pressure and force data on the effect of crossflow on the fountain induced lift and suckdown. The analysis includes the effects of jet spacing, height and operating conditions. However, it is limited to twin jet configurations of circular, vertical jets operating at subcritical nozzle pressure ratios over a fixed ground surface.
    Keywords: Aerodynamics
    Type: NASA/CR-1998-206955 , A-98-09726 , NAS 1.26:206955
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Semiempirical Procedure for Estimating Lift and Drag Characteristics of Propeller-Wing-Flap Configurations for Vertical-and Short-Take-Off-and-Landing Airplanes (1959)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: The analysis presented uses the momentum theory as a starting point in developing semiempirical expressions for calculating the effect of propeller thrust and slipstream on the lift and drag characteristics of wing-flap configurations that would be suitable for vertical-take-off-and-landing (VTOL) and short-take-off-and-landing (STOL) airplanes. The method uses power-off forward-speed information and measured slipstream deflection data at zero forward speed to provide a basis for estimating the lift and drag at combined forward speed and power-on conditions. A correlation of slipstream deflection data is also included. The procedure is applicable only in the unstalled flight regime; nevertheless, it should be useful in preliminary design estimates of the performance that may be expected of VTOL and STOL airplanes.
    Keywords: Aerodynamics
    Type: NASA-MEMO-1-16-59L , L-144
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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