Lab Home | Phone | Search
 Current Affiliates Alumni Visitors Students
 2007 2006 2005 2004 2003 2002 2001 2000 <1999
 Colloquia Colloquia Archive Seminars Postdoc Seminars Archive Quantum Lunch CMS Colloquia Q-Mat Seminars Q-Mat Seminars Archive Archive

 Description Past Visitors

Monday, March 10, 2008
3:00 PM - 4:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Colloquium

Hyperviscosity, Galerkin truncation and bottlenecks

Uriel Frisch
Observatoire de la Cote d'Azur

It is shown that the replacement in hydrodynamical equations of the usual dissipation by a high power $\alpha$ of the Laplacian leads asymptotically to truncating the dynamics to a a finite number of Fourier modes. When this number is large, a range of thermalized modes appear through the mechanism discovered by Cichowlas et al. [PRL 95, 264502, 2005]. The dynamics at small and intermediate wavenumbers is governed by the ordinary Navier-Stokes equations but a huge bottleneck in thermal equilibrium with Gaussian statistics is present at large wavenumbers. The usual ($\alpha=1$) bottleneck can be viewed as an aborted thermalization. Practical implications for turbulence modelling are discussed. This material is based on work in collaboration with Susan Kurien and Jian-Zhou Zhu.

Host: Susan Kurien, T-7