Application of numerical wall functions for boundary layer flows with separation and reattachment

Abstract

This paper describes a numerical wall function method for RANS simulations of isothermal incompressible flows with separation and reattachment using an unstructured flow solver. The method is studied for the Spalart-Allmaras one-equation model and is implemented in Open FOAM®. For each wall node, a one-dimensional boundary-layer problem is integrated numerically on an embedded sub-grid in the near-wall region. The method is applied to the flow over a backward facing step, over a smoothly contoured ramp and over a NACA4412 airfoil to show the improvement of the results compared to universal wall functions.