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The Sound Generated by a Two-Dimensional Shear Layer: The Far Field Directivity from Computations and Acoustic Analogies

Colonius, Tim and Lele, Sanjiva K. and Moin, Parviz (1995) The Sound Generated by a Two-Dimensional Shear Layer: The Far Field Directivity from Computations and Acoustic Analogies. In: Computational Aeroacoustics. Vol.219. ASME , pp. 47-52.

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The sound generated by vortex pairing in a two- dimensional mixing layer is studied by direct numerical simulation of the Navier-Stokes equations (DNS) for the layer and a portion of its acoustic field, and by solving Lilley's equation (with source terms determined from the DNS) for the entire acoustic field. Predictions for the acoustic field based on Lilley's equation are in good agreement with the DNS results. The radiated acoustic field at the pairing frequencies is highly directive and cannot be produced by point quadrupole sources. Instead, it is of the superdirective character considered by Crighton and Huerre (1990, J. Fluid Mech., 220), where the magnitude of the pressure varies like the exponential of the cosine of the angle between the observation point and the downstream axis. By making modifications to this basic directivity, we account, in part, for shear in the mean velocity and the convection of the acoustic waves by the different freestream velocities on either side of the layer, and obtain a good overall agreement between the theory and the computations.

Item Type:Book Section
Colonius, Tim0000-0003-0326-3909
Moin, Parviz0000-0002-0491-7065
Additional Information:This work has been sponsored by the Office of Naval Research, grant N00014-92-J-1626, and computer time and support has been provided by the NASA Ames Research Center and the Center for Turbulence Research.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-92-J-1626
Record Number:CaltechAUTHORS:20190726-104730264
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97459
Deposited By: Melissa Ray
Deposited On:01 Aug 2019 17:07
Last Modified:20 Mar 2021 00:33

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