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An Analysis of the Pressures, Forces and Moments Induced by the Ground Vortex Generated by a Single Impinging JetWhen 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.
Document ID
19970021556
Acquisition Source
Ames Research Center
Document Type
Contractor Report (CR)
Authors
Kuhn, Richard E. (Defense Group, Inc. Arlington, VA United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1997
Subject Category
Aerodynamics
Report/Patent Number
A-975988
NAS 1.26:4765
NASA-CR-4765
Accession Number
97N22505
Funding Number(s)
CONTRACT_GRANT: NAS2-14384
PROJECT: RTOP 505-68-32
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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