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The elliptic whistler jet

Published online by Cambridge University Press:  25 October 1999

HYDER S. HUSAIN  and
FAZLE HUSSAIN
HYDER S. HUSAIN
Affiliation:
Mechanical Engineering Department, University of Houston, Houston, TX 77204-4792, USA
FAZLE HUSSAIN
Affiliation:
Mechanical Engineering Department, University of Houston, Houston, TX 77204-4792, USA
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Abstract

Elliptic jets have decided advantages for technological applications over circular jets; this paper explores further advantages achieved by jet forcing due to self-excitation. Using hot-wire measurements and flow visualization, we have studied an elliptic whistler (i.e. self-excited) air jet of 2:1 aspect ratio which, in contrast to an elliptic jet issuing from a contoured nozzle, displays no axis switching, but significantly increased spread in the major-axis plane. Its near-field mass entrainment is considerably higher (by as much as 70%) than that of a non-whistling jet. Flow visualization reveals unexpected dynamics of the elliptic vortical structures in the whistler jet compared to that in the non-whistling jet. Vortices rolled up from the lip of the elliptic pipe impinge onto the collar, producing secondary vortices; interaction of these two opposite-signed vortices is shown to cause the different behaviour of the whistler jet.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 397 , 25 October 1999 , pp. 23 - 44
Copyright
© 1999 Cambridge University Press

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