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Structure of a screeching rectangular jet: a stereoscopic particle image velocimetry study

Published online by Cambridge University Press:  30 July 2003

MEHMET B. ALKISLAR ,
ANJANEYULU KROTHAPALLI  and
LUIZ M. LOURENCO
MEHMET B. ALKISLAR
Affiliation:
Department of Mechanical Engineering, 2525 Pottsdamer Street, Florida A&M University and Florida State University, Tallahassee, FL 32310, USAalkislar@eng.fsu.edu
ANJANEYULU KROTHAPALLI
Affiliation:
Department of Mechanical Engineering, 2525 Pottsdamer Street, Florida A&M University and Florida State University, Tallahassee, FL 32310, USAkroth@eng.fsu.edu
LUIZ M. LOURENCO
Affiliation:
Department of Mechanical Engineering, 2525 Pottsdamer Street, Florida A&M University and Florida State University, Tallahassee, FL 32310, USA
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Abstract

The unsteady velocity field generated by an underexpanded jet has been investigated using stereoscopic particle image velocimetry (PIV). A 4:1 aspect ratio converging–diverging rectangular nozzle designed to operate at a fully expanded condition of $M=1.44$ was used. The nozzle was operated at off-design conditions to generate imperfectly expanded jets with intense screech tones. Phase-locked PIV measurements show the spatial and temporal evolution of the three-dimensional jet with high fidelity. In addition to the globally averaged mean and turbulence velocity field data, the phase-averaged data for the velocity and vorticity fields were also obtained. The turbulence quantities were resolved into contributions from the periodic and random motions. The deformation of the periodic spanwise structures results in the formation of strong streamwise vortices that appear to govern the mixing of the jet. It is shown that the presence of coherent vorticity of significant strength, in addition to the shock cell strength, is largely responsible for determining the screech intensity.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 489 , 25 July 2003 , pp. 121 - 154
Copyright
© 2003 Cambridge University Press

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