Large eddy simulation in a turbulent channel flow using exit boundary conditions

The influence of the exit boundary conditions on the vanishing first deriva tive of the velocity components and constant pressure on the large eddy sim ulation of the fully developed turbulent channel flow has been investigated for equidistant and stretched grids at the channel exit. Results show that the chosen exit boundary conditions introduce some small disturbances that are mostly damped by the grid stretching. The difference of rms values bet ween the fully developed turbulent channel flow with periodicity conditions and the fully developed channel flow using inlet and the exit boundary con ditions is less than 10% for the equidistant grids and less than 5% for the stretched grids. The chosen boundary conditions are of interest because th ey may be used in complex problems with back flow at the exit. Copyright (C ) 1999 John Wiley & Sons, Ltd.