Breakdown of continuity in large-eddy simulation

In numerical simulations of incompressible flows-both direct and large-eddy simulations (LES)-the pressure is determined to enforce the continuity constraint. In this paper it is shown that for many common LES representations, there is no exact continuity constraint on the LES field, and thus a straightforward application of the continuity equation introduces errors. It is suggested that these errors can be reduced by optimizing the approximate continuity equation used to determine the pressure in an LES. Various strategies for constructing these approximate constraints are explored. The techniques are demonstrated on forced isotropic turbulence with a coarse finite-volume representation, and the a priori errors of several approximate continuity constraints are presented. (C) 2001 American Institute of Physics.