Computation of turbulent flow around a square block with standard and modified k-ε turbulence models

Abstract

Two-dimensional Reynold Averaged Navier Stokes (RANS) turbulence model simulations for a flow past a square block with Re = 21400 are presented in this paper. An available modified k-ε turbulence model, which is an improved version of the standard k-ε turbulence model, is applied to simulate experiment cases of vortex shedding around a square block. The performance evaluation of the modified model is conducted by assessing its results with the results of the standard k-ε turbulence model based on the similarity with the experiment measurement data. It is found that the modified model improves the drag coefficient by about 16%, the Strouhal number by about 1.5%, and the length recirculation zone by about factor two compared to that of the standard model. The RMSE values indicate a significant improvement of the time averaged velocity along the centre line by about 59% and the velocity profile above the square block by about 6% when the modified model is applied. Generally, the modified k-ε model indicates advantages compared with the standard k-ε model. However, discrepancy is found between the model result and the experiment observation for the free stream velocity at downstream and it may be necessary to consider the 3D effect on turbulent fluctuation in further studies.