Effect of Different Near-Wall Treatments on Indoor 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 in building: (1) the first concerns flow through a long corridor which is similar to that in a fully developed plane channel. Simulation results are compared to direct numerical simulation (DNS) data of Moser et al. (1999) for Reτ = 590 (where Reτ denotes the friction Reynolds number defined by friction velocity uτ , kinematics viscosity ν and the channel half-width δ); (2) the second case is a benchmark test for room air distribution. Simulation results are compared to experimental data obtained with laser-Doppler anemometry (Nielsen, 1990). Simulations were performed with the aid of 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 of the first near-wall node are needed. Results of near-wall mean stream wise velocity u + and turbulent kinetic energy k + profiles are presented, variables with the superscript of + are those non dimensional by the wall friction velocity uτ and the kinematic viscosity ν.