Effect of aspect ratio on the aerodynamic characteristics of finite-length square cylinders

Abstract This study investigates the influence of aspect ratio on the aerodynamic characteristics of a finite-length square cylinder with free ends using computational fluid dynamics simulations at a Reynolds number of 6000. Aspect ratios from 12.5 to 2 are analyzed, revealing crucial insights into aerodynamic behavior under varying conditions. At an aspect ratio near 8, a major wake reorganization occurs, marking the dominant transition in the wake structure. Higher aspect ratios result in periodic shedding of coherent tip and spanwise vortices, forming a von Kármán vortex street. As the aspect ratio decreases, tip vortices migrate toward the leeward side, disrupting spanwise vortices and reducing vortex shedding. Below an aspect ratio of 8, steady loops of tip and spanwise vortices form, suppressing periodic shedding. The drag coefficient peaks at an aspect ratio of 12.5 and declines with decreasing aspect ratio, while the root mean square lift coefficient reaches zero below an aspect ratio of 6.5. The Strouhal number indicates no periodic vortex shedding below an aspect ratio of 4.5. Pressure distribution analysis reveals intricate patterns and changes in high-pressure regions. These findings highlight the crucial role of aspect ratio in aerodynamic behaviors, providing valuable insights for optimizing square cylinder designs in various engineering applications.