High-reynolds number flow around coated symmetrical hydrofoil: effect of streamwise slip on drag force and vortex structures

Abstract

Effects of slip on the flow around a symmetrical hydrofoil with a blunt trailing-edge are numerically investigated at Reynolds numbers of $$Re=5 \times {10^6}$$ , $$12.5 \times {10^6}$$ and $$25 \times {10^6}$$ based on the free-stream velocity and chord length. The simulations are performed by applying a two-dimensional Unsteady Reynolds–Averaged Navier–Stokes (URANS) approach and SST k–ω turbulence model. Furthermore, the Navier boundary condition with different slip lengths ( $${L_{\text{s}}}=\;{\text{2}},{\text{ 35 and 7}}0$$ µm) is employed on the surfaces. The results indicate that the Ls has a considerable effect on the integral parameters and a moderate influence on the wake flow structure. As such, a massive drag reduction (up to 47%) is observed, and an increase of Ls causes the increase of both frictional and pressure drag reduction rate. It is shown that a noticeable drag reduction can be achieved when the non-dimensional slip length is larger than one. The increment of slip length also leads to increase the amplitude of force fluctuations and frequency of vortex shedding; besides, the strength of vortex structures and the turbulence intensities are augmented.