UNSPECIFIED (1999) WKB theory for rapid distortion of inhomogeneous turbulence. JOURNAL OF FLUID MECHANICS, 390 . pp. 325-348. ISSN 0022-1120

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Abstract

A WKB method is used to extend RDT (rapid distortion theory) to initially inhomogeneous turbulence and unsteady mean flows. The WKB equations describe turbulence wavepackets which are transported by the mean velocity and have wavenumbers which evolve due to the mean strain. The turbulence also modifies the mean flow and generates large-scale vorticity via the averaged Reynolds stress tensor. The theory is applied to Taylor's four-roller flow in order to explain the experimentally observed reduction in the mean strain. The strain reduction occurs due to the formation of a large-scale vortex quadrupole structure from the turbulent spot confined by the four rollers. Both turbulence inhomogeneity and three-dimensionality are shown to be important for this effect. If the initially isotropic turbulence is either homogeneous in space or two-dimensional, it has no effect on the large-scale strain. Furthermore, the turbulent kinetic energy is conserved in the two-dimensional case, which has important consequences for the theory of two-dimensional turbulence. The analytical and numerical results presented here are in good qualitative agreement with experiment.

Item Type:	Journal Article
Subjects:	T Technology > TJ Mechanical engineering and machinery Q Science > QC Physics
Journal or Publication Title:	JOURNAL OF FLUID MECHANICS
Publisher:	CAMBRIDGE UNIV PRESS
ISSN:	0022-1120
Date:	10 July 1999
Volume:	390
Number of Pages:	24
Page Range:	pp. 325-348
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/14329

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