Computations of a laminar backward-facing step flow at Re=800 with a spectral domain decomposition method

The two-dimensional laminar incompressible flow over a backward-facing step is computed using a spectral domain decomposition approach. A minimum numb er of subdomains (two) is used; high resolution being achieved by increasin g the order of the basis Chebyshev polynomial. Results for the case of a Re ynolds number of 800 are presented and compared in detail with benchmark co mputations. Stable accurate steady flow solutions were obtained using subst antially fewer nodes than in previously reported simulations. In addition, the problem of outflow boundary conditions was examined on a shortened doma in. Because of their more global nature, spectral methods are particularly sensitive to imposed boundary conditions, which may be exploited in examini ng the effect of artificial (non-physical) outflow boundary conditions. Two widely used set of conditions were tested: pseudo stress-free conditions a nd zero normal gradient conditions. Contrary to previous results using the finite volume approach, the latter is found to yield a qualitatively errone ous yet stable flow-field. Copyright (C) 1999 John Wiley & Sons, Ltd.