Time-accurate intermediate boundary conditions for large eddy simulations based on projection methods

Projection methods are among the most adopted procedures for solving the Navier-Stokes equations system for incompressible flows. In order to simplify the numerical procedures, the pressure-velocity decoupling is often obtained by adopting a fractional time-step method. In a specific formulation, suitable for the incompressible flows equations, it is based on a formal decomposition of the momentum equation, which is related to the Helmholtz-Hodge Decomposition theorem of a vector field in a finite domain. Owing to the continuity constraint also in large eddy simulation of turbulence, as happens for laminar solutions, the filtered pressure characterizes itself only as a Lagrange multiplier, not a thermodynamic state variable. The paper illustrates the implications of adopting such procedures when the decoupling is performed onto the filtered equations system. This task is particularly complicated by the discretization of the time integral of the sub-grid scale tensor. A new proposal for developing time-accurate and congruent intermediate boundary conditions is addressed. Several tests for periodic and non-periodic channel flows are presented. Copyright (c) 2005 John Wiley & Sons, Ltd.