Unsteady RANS simulations of flow around rectangular cylinders with different aspect ratios

Abstract

Flow around rectangular cylinders with different aspect ratios has been investigated using the two-dimensional (2D) Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the k–ω Shear Stress Transport (SST) turbulence model. The aspect ratios (R=B/H, where B and H are the breadth and height of the cross-sections in the streamwise and cross-stream directions, respectively) of the cross-sections vary from 1 to 0.05. The Reynolds number (Re) based on the free stream velocity and H is 21,400. The objective of the present study is to evaluate the validity of 2D URANS simulations with k–ω SST model for the flow around rectangular cylinders. The drag forces acting on the cylinders with high aspect ratios (i.e. R=1, 0.8 and 0.6) are well predicted by the present simulations; however, the drag forces are overpredicted for low aspect ratios (i.e. R=0.4, 0.2, 0.1 and 0.05). The vortex shedding frequencies are not sensitive to the aspect ratio, and the values calculated in the present simulations are in good agreement with the published results. The effects of aspect ratios on the vortex formation have also been discussed.