Investigation of subcritical flow regime and force characteristics of square cylinder with various corner modification techniques

Abstract

Corner modifications are effective strategies for mitigating flow-induced forces and vibrations, thereby ensuring structural safety in ocean engineering. However, the flow mechanism associated with these modifications for subcritical Reynolds flow remain inadequately understood. This study employs large eddy simulation (LES) to evaluate the flow structure and fluid-induced forces of a square cylinder with different corner modifications, including rounded, chamfered, step cut corner, and corner ribs, at a Reynolds number of R_e = 2.2 × 10⁴. The results indicate that both front and four corner modifications notably alter flow structures and flow stability, characterized by elongated wake vortices and less vigorous flapping of the shear layer. For rounded and chamfered corners, the models with front and four corner modifications exhibit similar flow behaviors and force characteristics. However, for step cut corners and corner ribs, modifications to the rear corners further modify the flow structure compared with those addressing only the front corners. The four step cut corners and corner ribs can induce local recirculation inside the modified corners, which is critical in modifying the flow topology, shear layer behavior, pressure distribution, and resultant forces. The study concludes that front step cut and four corner ribs are optimal strategies for flow control, achieving force reduction ratios of 38.3 % for drag ${\bar{C}}_d$ and 84.3 % for lift C'_l in the model with four corner ribs. Furthermore, the rib significantly influences the wake vortex and force characteristics, with deeper ribs improving flow dynamics, reducing vortex intensity, and lowering wall pressure and fluid-induced forces. These findings offer valuable insights for the design and implementation of flow control methods in ocean engineering.