Flow pattern- and forces-susceptibility to small attack angles for a rectangular cylinder

This study employs numerical simulation to investigate the two-dimensional flow of a rectangular cylinder with an aspect ratio of 5, under various flow attack angles (α) and Reynolds numbers. The lift and drag coefficients, surface pressure distributions, and flow structures are analyzed using the HODMD method. The findings suggest that a rise in flow attack angle increases the lift and drag coefficients of rectangular cylinders, but the turning point of the Reynolds number leads to an opposite trend in the increase of drag coefficients. The sensitivity of the flow field is intricately related to the Reynolds number and flow attack angle. Additionally, the increase in both Reynolds number and flow attack angle enhances the complexity of the flow structure, particularly at the trailing edge, which is a sensitive part of applying flow control. HODMD analysis shows that the first three modes dominate dynamics. Odd-order modes contribute significantly to lift at low α, while even-order modes cancel each other. As α increases, the contributing modes of lift gradually shift from odd to even order. This study provides valuable insights for prospective flow control strategies and addresses vibration concerns in associated submerged structures. © 2024 Elsevier Ltd.