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Exact coherent structures in channel flow

Published online by Cambridge University Press:  22 June 2001

FABIAN WALEFFE
Affiliation:
Departments of Mathematics and Engineering Physics, 819 Van Vleck Hall, University of Wisconsin, Madison WI 53706, USA

Abstract

Exact coherent states in no-slip plane Poiseuille flow are calculated by homotopy from free-slip to no-slip boundary conditions. These coherent states are unstable travelling waves. They consist of wavy low-speed streaks flanked by staggered streamwise vortices closely resembling the asymmetric coherent structures observed in the near-wall region of turbulent flows. The travelling waves arise from a saddle-node bifurcation at a sub-turbulent Reynolds number with wall-normal, spanwise and streamwise dimensions smaller than but comparable to 50+, 100+ and 250+, respectively. These coherent solutions come in pairs with distinct structure and instabilities. There is a three-dimensional continuum of such exact coherent states.

Type
Research Article
Copyright
© 2001 Cambridge University Press

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