System reduction strategy for Galerkin models of fluid flows

We propose a system reduction strategy for spectral and Galerkin models of incompressible fluid flows. This approach leads to dynamic models of lower order, based on a partition in slow, dominant and fast modes. In the reduced models, slow dynamics are incorporated as non-linear manifold consistent with mean-field theory. Fast dynamics are stochastically treated and can be lumped in eddy-viscosity approaches. The employed interaction models between slow, dominant and fast dynamics respect momentum and energy balance equations in a mathematically rigorous manner unlike unsteady Reynolds-averaged Navier-Stokes models or Smagorinsky-type reductions of the Navier Stokes equation. The proposed system reduction strategy is employed to the cylinder wake benchmark. Copyright (C) 2009 John Wiley & Sons, Ltd.