Dynamic Eduction Of Coherent Structures In Turbulent Jet Flow Imagery By Wavelet Techniques: Part I

Srinivas, Arun and Bhat, GS and Narasimha, Roddam (2007) Dynamic Eduction Of Coherent Structures In Turbulent Jet Flow Imagery By Wavelet Techniques: Part I. In: Journal of Turbulence, 8 (15). pp. 1-14.

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Abstract

The use of two-dimensional wavelet techniques enables us to discern, at appropriate wavelet scales, certain features of a coherent structure from a single flow visualization image. By analysing a large number of planar laser-induced fluorescence images of chiefly the diametral section of a turbulent jet, with some supplementary axial sections, we show that it is possible to describe the passage of whole coherent structures through a specified section of the flow, and thereby acquire useful information on their life cycle. In particular it is found that a typical cycle is characterized by a lobed ring-like structure about 8% of the time, a dye-filled core a similar fraction of the time, with a mixed regime in between. Based on comparisons with dye-concentration data and DNS results, it is suggested that the lobed ring seen in the wavelet transform of the raw image may represent a vortex ring exhibiting the Widnall instability.

Item Type:	Journal Article
Publication:	Journal of Turbulence
Publisher:	Taylor & Francis
Additional Information:	Copyright of this article belongs to Taylor & Francis.
Keywords:	Coherent structures;Wavelet techniques;Turbulent jet.
Department/Centre:	Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	22 Jul 2008
Last Modified:	18 Oct 2010 06:29
URI:	http://eprints.iisc.ac.in/id/eprint/15195

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