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The scattering of sound waves by a vortex: numerical simulations and analytical solutions

Published online by Cambridge University Press:  26 April 2006

Tim Colonius
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
Sanjiva K. Lele
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
Parviz Moin
Affiliation:
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA

Abstract

The scattering of plane sound waves by a vortex is investigated by solving the compressible Navier–-Stokes equations numerically, and analytically with asymptotic expansions. Numerical errors associated with discretization and boundary conditions are made small by using high-order-accurate spatial differentiation and time marching schemes along with accurate non-reflecting boundary conditions. The accuracy of computations of flow fields with acoustic waves of amplitude five orders of magnitude smaller than the hydrodynamic fluctuations is directly verified. The properties of the scattered field are examined in detail. The results reveal inadequacies in previous vortex scattering theories when the circulation of the vortex is non-zero and refraction by the slowly decaying vortex flow field is important. Approximate analytical solutions that account for the refraction effect are developed and found to be in good agreement with the computations and experiments.

Type
Research Article
Copyright
© 1994 Cambridge University Press

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