Three-Dimensional Numerical Study of Flow Characteristics Around Finite and Infinite Circular Cylinders at Subcritical Reynolds Numbers

This study numerically investigates the three-dimensional flow characteristics around circular cylinders of finite- and infinite-lengths under subcritical Reynolds numbers using the SST kappa-omega turbulence model within OpenFOAM. The simulations were conducted for aspect ratios (ARs) of 2, 5, and 10 and Reynolds numbers (Re) of 1 x 104, 3 x 104, 5 x 104, and 1 x 105. Under infinite conditions, the drag coefficient (Cd) and lift coefficient (Cl) exhibit Cl ear transitions from steady to unsteady flow regimes as Re increases, driven by organized vortex shedding. For finite conditions, the presence of a free end significantly alters the flow, inducing strong three-dimensional effects such as high-velocity regions near the end surface and complex vortex structures. The Cd and Cl trends for finite cylinders show reduced values and slower convergence compared to infinite cases due to free end interference. Additionally, the vortex density near the fixed boundary intensifies with increasing Re. These findings provide a comparative understanding of flow dynamics in finite and infinite cases, offering insights into the design of offshore structures.