Effect of tip-gap height on tip-leakage flows in a stationary NACA hydrofoil

This paper presents a numerical study on the tip-leakage flow (TLF) for distinct tip-gap heights of a stationary hydrofoil. Steady-state simulations using the Reynolds-averaged Navier-Stokes turbulence model were performed to evolve the computations. The extensions of the tip-leakage vortex (TLV) and tip-separation vortices (TSVs) increased for larger tip-gap heights. Conversely, additional vortices were yielded for the smallest gap height evaluated. The lower coefficient of the minimum pressure value in the TLV was observed for the larger tip-gap heights. A downward flow region expanded with a higher peak value near the TSVs on the suction side for the larger tip gap. Thus, the spin of the TLV could be further strengthened. The low velocity flow in the boundary layer was entrained into the TLV for the smaller tip gap, whereas the low-turbulence flow in the mainstream crossed the gap and was entrained into the TLV for the larger tip gap.