Evaluation and limitations of standard wall functions in channel and step flow configurations

Abstract

This paper reviews and investigates the implementation, evaluation and limitations of conventional wall functions, based on law of the wall, in combination with linear k-ε turbulence model in simple (fully developed channel) and complex (backward facing step) flow configurations. The near-wall viscosity-affected layer of a turbulent fluid flow poses a number of challenges, from both modeling and numerical viewpoints. Over this thin wall-adjacent region turbulence properties change orders of magnitude faster than over the rest of the flow. Although the law of the wall and equilibrium assumptions are not valid in the recirculation region of the separating and reattaching flows, the general flow behaviour of backward-facing step flow is not significantly altered by the particular form of the standard wall functions. The results obtained in the case of the backward facing step flow configuration suggest that the solution might be found in modification of the linear k-ε model and improvement of standard wall functions.