Multiscale computation of isotropic homogeneous turbulent flow

In this article we perform a systematic multi-scale analysis and computation for incompressible Euler equations and Navier-Stokes Equations in both 2D and 3D. The initial condition for velocity field has multiple length scales. By reparameterizing them in the Fourier space, we can formally organize the initial condition into two scales with the fast scale component being periodic. By making an appropriate multiscale expansion for the velocity field, we show that the two-scale structure is preserved dynamically. Moreover, we derive a well-posed homogenized equation for the incompressible Euler equations in the Eulerian formulations. Numerical experiments are presented to demonstrate that the homogenized equations indeed capture the correct averaged solution of the incompressible Euler and Navier Stokes equations. Moreover, our multiscale analysis reveals some interesting structure for the Reynolds stress terms, which provides a theoretical base for establishing an effective LES type of model for incompressible fluid flows.