Taper ratio effects on cavitating flow and hydrodynamics of a wedge-shaped fin

An unsteady Reynolds-averaged Navier–Stokes (URANS) approach coupled with the k-ε turbulence model in OpenFOAM is employed to investigate the effects of taper ratio on the cavitating-flow characteristics and hydrodynamic performance of a wedge-shaped control fin. Three taper ratios ( λ = 0.35, 0.65, 1.00) are considered over a range of angles of attack ( α = 0°, 5°, 10°, and 15°) and cavitation numbers ( σ = 0.48, 0.66, 0.98, and 1.41). The results demonstrate that tapering significantly modifies cavity development through changes in the spanwise pressure distribution and three-dimensional flow structures. Cavity-volume analysis reveals that the influence of taper ratio depends on the cavitation regime, with strong tapering generally suppressing cavity development under moderate cavitation conditions but exhibiting a more complex response under fully developed cavitation. The high-turbulent-kinetic-energy region shifts from the tip toward the root as the taper ratio increases. Tapering also modifies vortex dynamics, producing root leading-edge vortices and tip-vortex fragmentation, in contrast to the more coherent vortical structures of the untapered fin. Decreasing the taper ratio generally reduces drag, improves the lift-to-drag ratio, and suppresses large-amplitude fluctuations in global hydrodynamic loading. These findings clarify the relationships among geometric modification, pressure redistribution, vortex dynamics, cavitation behavior, and hydrodynamic performance, providing new insight into tapered control fins operating under cavitating conditions.