Effect of near-wall treatments on airflow simulations

Abstract

Airflow simulation results depend on a good prediction of near wall turbulence. In this paper a comparative study between different near wall treatments is presented. It is applied to two test cases: (1) the first concerns the fully developed plane channel flow (i.e. the flow between two infinitely large plates). Simulation results are compared to direct numerical simulation (DNS) data of Moser et al. (1999) for $Re\tau$ = 590 (where $Re\tau$ denotes the friction Reynolds number defined by friction velocity $u\tau$, kinematics viscosity $v$ and the channel half-width $\delta$); (2) the second case is a benchmark test for room air distribution (Nielsen, 1990). Simulation results are compared to experimental data obtained with laser-doppler anemometry. Simulations were performed with the aid of the commercial CFD code Fluent (2005). Near wall treatments available in Fluent were tested: Standard Wall Functions, Non Equilibrium Wall Function and Enhanced Wall Treatment. In each case, suitable meshes with adequate position for the first near-wall node are needed. Results of near-wall mean streamwise velocity U+ and turbulent kinetic energy k+ profiles are presented, variables with the superscript of + are those non dimensional by the wall friction velocity $u\tau$ and the kinematic viscosity {\nu}.