Numerical investigation of vortical evolution in a backward-facing step expansion flow

A numerical investigation of laminar flow over a backward-facing step is pr esented for the Reynolds number in the range of 50 less than or equal to Re less than or equal to 2500. The objective of this numerical investigation is to add to the existing knowledge of the backward-facing step flow to dee pen our understanding of the expansion flow structure. We proceed with the analysis by verifying the computer code through the Pearson vortex problem. We then perform a parametric study by varying the Reynolds number, with th e aim of determining whether or not there exists a critical Reynolds number , above which reattachment length on the channel floor decreases. We also c oncentrate on subjects that have been little explored in the flow, examples of which are the onset of a single vortex in the primary eddy and how the recirculating bubble containing flow reversals is torn into smaller eddies. Eddy distortion, leading to mobile saddle points, and the merging of eddie s are also discussed in this study. (C) 1999 Elsevier Science Inc. All righ ts reserved.