Bifurcation of low reynolds number flows in symmetric channels

The flowfields in two-dimensional channels with discontinuous expansions are studied numerically to understand how the channel expansion ratio influences the symmetric and nonsymmetric solutions that are known to occur. For improved confidence and understanding, two distinct numerical techniques are used. The general flowfield characteristics in both symmetric and asymmetric regimes are ascertained by a time-marching finite difference procedure. The flowfields and the bifurcation structure of the steady solutions of the Navier-Stokes equations are determined independently using the finite element technique. The two procedures are then compared both as to their predicted critical Reynolds numbers and the resulting flowfield characteristics. Following this, both numerical procedures are compared with experiments. The results show that the critical Reynolds number decreases with increasing channel expansion ratio. At a fixed supercritical Reynolds number, the location at which the jet first impinges on the channel wall grows with the expansion ratio.