Monday, March 10, 20083:00 PM - 4:00 PMCNLS Conference Room (TA-3, Bldg 1690)|
Hyperviscosity, Galerkin truncation and bottlenecks
Uriel FrischObservatoire 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