Spanwise length and mesh resolution effects on simulated flow around a 5:1 rectangular cylinder

Abstract

For a 5:1 rectangular cylinder, the large eddy simulations (LES) are carried out to systematically evaluate the influences of the cylinder spanwise length (L) and spanwise mesh size (δz) on the aerodynamic forces, spanwise-averaged quantities, and flow features. The L varies from 10D to 2.5D, and δz varies from 0.1D to 0.0125D, where D is the cylinder depth. The new simulation cases of L ​= ​2.5D and δz ​= ​0.025D, 0.0125D are firstly attempted in this study. Some flow details are unveiled through flow visualization and spanwise correlation functions of the surface pressure. The simulation accuracy is validated through the comparisons of the surface pressure, velocity profile in wake region, and relative phase angle distributions on the cylinder top face with the available experimental results. It was found that the influence of L is in general insignificant, while δz has more significant effects on the surface pressure fluctuation, main separation bubble size, and 3D flow features. In consideration of both simulation accuracy and computation time, 2.5D and 0.025D are recommended for the selections of L and δz, respectively. The results based on the more refined grids in this study could serve as references for evaluating the accuracies of other numerical simulations.