Spatial resolution effects on unsteady turbulent flow computations for the rectangular cylinders byκ-ε turbulence models

In predicting unsteady turbulent flows around a square cylinder usingκ-ε turbulence models, choice of right turbulence models was found to be critical. If a proper care is taken to choose a convection scheme and near-wall resolution, the conventional turbulence models may predict an unsteady turbulent flow at low Reynolds numbers with reasonable accuracy. A systematic computation is carried out to identify the effects of the aspect ratio of a rectangular cylinder and of the flow Reynold number on the spatial resolution requirement. It is found in general that the grid resolution requirement is more stringent for a cylinder with a smaller aspect ratio. By investigating high Reynolds number computations, the grid refinement in terms of viscous wall units is found unimportant in accurately predicting the unsteady aerodynamic forces on the cylinder. Instead, resolution of shear layers formed at the forward separation corners is found to be more critical.