The Wells turbine is one of the candidates for use in Oscillating Water Column (OWC) type wave energy conversion devices. The limited operating range of Wells turbines poses a significant constraint on their usage in OWCs. Reducing the over tip leakage flow is crucial for enhancing the wells turbine performance as it promotes the flow separation. In the present investigation, the concept of a partial cavity tip was introduced and its effectiveness was assessed across varying depths of the cavity, while considering stall delay, power production, and efficiency as performance metrics. Three distinct designs were evaluated: a cavity tip, a partial cavity tip provided on the leading edge, and a partial cavity provided on the trailing edge. Computational simulations of the flow through the turbine annulus were conducted and compared to previous experimental results obtained from the reference turbine. The simulations employed the three-dimensional Reynolds-averaged Navier–Stokes equations, utilizing a two-equation turbulence closure model available in ANSYS CFX 18.1. The computational domain was discretized using unstructured tetrahedral elements, and an optimized grid was achieved through a grid independence study. While both the cavity tip and the partial cavity tip on leading edge had a detrimental impact on the turbine’s performance, the partial cavity tip on the trailing edge resulted in an overall average efficiency improvement of 6.25%.