Numerical study of three recirculation zones in the unilateral sudden expansion flow

Numerical simulations of the two-dimensional laminar flow over a backward-facing step channel using two commercially-available Computational Fluid Dynamics (CFD) code are reported. The subject is to analyze the three recirculation regions of the flow in a unilateral sudden expansion. Results are presented for laminar air flow for Reynolds number lower than 2500. The mathematical model equations (mass conservation and momentum) were solved with finite element (FEM) and finite volume (FVM) methods and a segregated approach. To get the grid independent, intensive refinement studies were carried out. Results obtained are compared to experimental data presenting a good agreement. The numerical results of this work show a non-linear increase of the reattachment length as also shown by the experimental results extracted from literature.