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Pattern-recognized structures in bounded turbulent shear flows

Published online by Cambridge University Press:  12 April 2006

James M. Wallace
Affiliation:
Department of Mechanical Engineering, University of Maryland, College Park
Robert S. Brodkey
Affiliation:
Department of Chemical Engineering, The Ohio State University, Columbus
Helmut Eckelmann
Affiliation:
Max-Planck-Institut für Strömungsforschung, D3400 Göttingen, Germany

Abstract

It is now well established that coherent structures exist in turbulent shear flows. It should be possible to recognize these in the turbulence signals and to program a computer to extract and ensemble average the corresponding portions of the signals in order to obtain the characteristics of the structures. In this work only the u-signal patterns are recognized, using several simple criteria; simultaneously, however, the v or w signals as well as uv or uw are also processed. It is found that simple signal shapes describe the turbulence structures on the average. The u-signal pattern consists of a gradual deceleration from a local maximum followed by a strong acceleration. This pattern is found in over 65% of the total sample in the region of high Reynolds-stress production. The v signal is found to be approximately 180° out of phase with the u signal. These signal shapes can be easily associated with the coherent structures that have been observed visually. Their details have been enhanced by quadrant truncating. These results are compared with randomly generated signals processed by the same method.

Type
Research Article
Copyright
© 1977 Cambridge University Press

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