Numerical Investigation of Hydrodynamic Characteristics of Circular Cylinder with Surface Roughness at Subcritical Reynolds Number

This study investigates the hydrodynamic behavior of rough cylinders, focusing on how surface roughness influences vortex shedding patterns and forces in cross-flow. To achieve this objective, a three-dimensional large-eddy simulation was conducted to study the hydrodynamic coefficients and flow fields of cylinders with different relative roughness, height, and coverage ratios at a Reynolds number of 3900. The results show that the coverage ratio plays a more significant role in determining hydrodynamic characteristics than relative roughness, with a critical coverage ratio identified at approximately 0.4. Below this threshold, both drag and lift coefficients exhibit a marked increase with higher relative roughness. However, beyond a 0.4 coverage ratio, the impact of roughness diminishes, with the coefficients approaching those of a smooth cylinder. Additionally, the Strouhal number decreases with increasing roughness height and increases with coverage ratio. Flow visualization shows that these changes are closely related to the position and magnitude of the wake vortex shedding in the wake region of a rough cylinder. These findings provide new insights into the fundamental mechanisms of the hydrodynamic characteristics and vortex shedding of rough cylinders and offer valuable guidance for optimizing engineering design and enhancing performance in practical applications.