Usability of explicit filtering in large eddy simulation with a low-order numerical scheme and different subgrid-scale models

Based on a priori tests, in large eddy simulation (LES) Of turbulent fluid flow, the numerical error related to low-order finite-difference-type methods can be large in comparison with the effect of subgrid-scale (SGS) model. Explicit filtering has been suggested to reduce the error, and it has shown promising results in a priori studies and in some simulations with fourth-order method. In this paper, the effect of explicit filtering on the total simulation error is studied together with a second-order scheme, where the numerical error should be even larger. The fully developed turbulent channel flow between two parallel walls is used as a test case. Rather simple SGS models are applied, because these models are most likely used in practical applications of LES. Explicit filtering is here applied to the non-linear convection term of the Navier-Stokes equations, four three-dimensional filter functions are applied, and the effect of filtering is separated from the effect of SGS modelling. It is shown that the effect of filtering is rather large and smooth filters introduce an additional error component that increases the total Simulation error. Finally, filtering via subfilter-scale modelling is applied, and it is shown that this approach performs better. However, the large-frequency components of the resolved flow field are not as effectively damped as when the non-linear convection term is filtered. Copyright (C) 2007 John Wiley & Sons, Ltd.