Instability of the perfect subgrid model in implicit-filtering large eddy simulation of geostrophic turbulence

Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Apr;75(4 Pt 2):046303. doi: 10.1103/PhysRevE.75.046303. Epub 2007 Apr 6.

Abstract

We demonstrate, in the context of implicit-filtering large eddy simulations (LESs) of geostrophic turbulence, that while the attractor of a well-resolved statistically stationary turbulent flow can be reached in a coarsely resolved LES that is forced by the subgrid scale (SGS) terms diagnosed from the well-resolved computation, the attractor is generically unstable: the coarsely resolved LES system forced by the diagnosed SGS eddy terms has multiple attractors. This points to the importance of interpreting the diagnosed SGS forcing terms in a well-resolved computation or experiment from a combined physical-numerical point of view rather than from a purely physical point of view.