Approximation of the larger eddies in fluid motions II: A model for space-filtered flow

We present two modifications of continuum models used in large eddy simulat ion. The first modification is a closure approximation which better attenua tes small eddies. The second modification is a change in the boundary condi tions for the large eddy model from strict adherence to slip with resistanc e. For model consistency, the resistance coefficient is a function of the a veraging radius so that the model's boundary conditions reduce to a no-slip as the averaging radius decreases to zero.