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DY: Dynamik und Statistische Physik

DY 10: Fluid Dynamics I

DY 10.4: Talk

Friday, March 4, 2005, 11:00–11:15, TU H3010

Linear stability of viscoelastic shear flows — •Juergen Buehrle — AG Komplexe Systeme, Philipps-Universität Marburg

The linear perturbation of a plane shear flow is decomposed into vortices and streaks. Their amplitudes decay exponentially at large times. At the same time, non-normal amplification of streaks leads to a transient growth, such that the maximum value of the kinetic energy associated with the perturbation exceeds its initial value by several orders of magnitude. For Newtonian fluids the maximum amplification occurs, when the width of the vortices is of the order of the channel height. We find, that for viscoelastic fluids the optimal vortex width is significantly larger. This motivates a different approach to the understanding of the transition to turbulence in viscoelastic flow.