Numerical sensitivity analysis of 3- and 2- dimensional rib-roughened channels

Abstract

Rough surfaces have been used as a tool to enhance heat transfer by increasing the level of turbulence mixing in the flow. In numerically simulating such flows, it is common to simulate a 3D rib-roughened channel with a 2D domain in order to reduce the computational time and power. The main purpose of the present work is to investigate the accuracy of the above approximation. In order to do so, initially a 3D channel is simulated using Reynolds-Averaged Navier–Stokes technique and comparison is made against 2D simulations as well as experimental data. In addition, the effects of rib thermal boundary condition and near-wall treatments are also investigated. All computations are undertaken using the commercial CFD code ‘STAR-CD’. The Reynolds number, based on the channel bulk velocity and hydraulic diameter, is 30,000. Two low-Reynolds-number linear Eddy–Viscosity Models, namely the Lien–Chen–Leschziner k − e model and a variant of Durbin’s v 2 − f formulation are used. In the CFD simulations reported here, the focus is on the experimental data of Rau et al. (ASME J Turbomach 120:368–375, 1998). It was found that the present results for a 3D channel are in relatively good agreement with the data. It was also shown that a 2D channel can be used to represent the flow in the centre-line of a 3D channel with relatively good accuracy.