Numerical simulations of laminar flow over a 3D backward-facing step

✍ Scribed by P. T. Williams; A. J. Baker

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 742 KB
• Volume: 24
• Category: Article
• ISSN: 0271-2091
• DOI: 10.1002/(sici)1097-0363(19970615)24:11<1159::aid-fld534>3.0.co;2-r

✦ Synopsis

A numerical investigation of laminar flow over a three-dimensional backward-facing step is presented with comparisons with detailed experimental data, available in the literature, serving to validate the numerical results. The continuity constraint method, implemented via a finite element weak statement, was employed to solve the unsteady three-dimensional Navier-Stokes equations for incompressible laminar isothermal flow. Twodimensional numerical simulations of this step geometry underestimate the experimentally determined extent of the primary separation region for Reynolds numbers Re greater than 400. It has been postulated that this disagreement between physical and computational experiments is due to the onset of three-dimensional flow near Re 400. This paper presents a full three-dimensional simulation of the step geometry for 100 4Re4800 and correctly predicts the primary reattachment lengths, thus confirming the influence of three-dimensionality. Previous numerical studies have discussed possible instability modes which could induce a sudden onset of three-dimensional flow at certain critical Reynolds numbers. The current study explores the influence of the sidewall on the development of three-dimensional flow for Re > 400. Of particular interest is the characterization of three-dimensional vortices in the primary separation region immediately downstream of the step. The complex interaction of a wall jet, located at the step plane near the sidewall, with the mainstream flow reveals a mechanism for the increasing penetration (with increasing Reynolds number) of three-dimensional flow structures into a region of essentially two-dimensional flow near the midplane of the channel. The character and extent of the sidewall-induced flow are investigated for 100 4Re4800.