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Flow field and noise characteristics of a supersonic impinging jet

Published online by Cambridge University Press:  10 August 1999

A. KROTHAPALLI ,
E. RAJKUPERAN ,
F. ALVI  and
L. LOURENCO
A. KROTHAPALLI
Affiliation:
Department of Mechanical Engineering, Florida A & M University and Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA; e-mail: kroth@fmrl.fsu.edu
E. RAJKUPERAN
Affiliation:
Department of Mechanical Engineering, Florida A & M University and Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA; e-mail: kroth@fmrl.fsu.edu
F. ALVI
Affiliation:
Department of Mechanical Engineering, Florida A & M University and Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA; e-mail: kroth@fmrl.fsu.edu
L. LOURENCO
Affiliation:
Department of Mechanical Engineering, Florida A & M University and Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA; e-mail: kroth@fmrl.fsu.edu
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Abstract

This paper describes the results of a study examining the flow and acoustic characteristics of an axisymmetric supersonic jet issuing from a sonic and a Mach 1.5 converging–diverging (C–D) nozzle and impinging on a ground plane. Emphasis is placed on the Mach 1.5 nozzle with the sonic nozzle used mainly for comparison. A large-diameter circular plate was attached at the nozzle exit to measure the forces generated on the plate owing to jet impingement. The experimental results described in this paper include lift loss, particle image velocimetry (PIV) and acoustic measurements. Suckdown forces as high as 60% of the primary jet thrust were measured when the ground plane was very close to the jet exit. The PIV measurements were used to explain the increase in suckdown forces due to high entrainment velocities. The self-sustained oscillatory frequencies of the impinging jet were predicted using a feedback loop that uses the measured convection velocities of the large-scale coherent vortical structures in the jet shear layer. Nearfield acoustic measurements indicate that the presence of the ground plane increases the overall sound pressure levels (OASPL) by approximately 8 dB relative to a corresponding free jet. For moderately underexpanded jets, the influence of the shock cells on the important flow features was found to be negligible except for close proximity of the ground plane.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 392 , 10 August 1999 , pp. 155 - 181
Copyright
© 1999 Cambridge University Press

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