Vortex shedding from a hydrofoil at high Reynolds number

Abstract

High Reynolds number (Re) wall-bounded turbulent flows occur in many hydro- and aerodynamic applications. However, the limited amount of high-Re experimental data has hampered the development and validation of scaling laws and modelling techniques applicable to such flows. This paper presents measurements of the turbulent flow near the trailing edge of a two-dimensional lifting surface at chord-based Reynolds numbers, Re$_{C}$, typical of heavy-lift aircraft wings and full-scale ship propellers. The experiments were conducted in the William B. Morgan Large Cavitation Channel at flow speeds from 0.50 to 18.3ms$^{-1}$ with a cambered hydrofoil having a 3.05m span and a 2.13m chord that generated 60 metric tons of lift at the highest flow speed, Re$_{C}{\approx}50{\times}10^{6}$. Flow-field measurements concentrated on the foil's near wake and include results from trailing edges having terminating bevel angles of 44$^{\circ}$ and 56$^{\circ}$. Although generic turbulent boundary layer and wake characteristics were found at any fixed Re$_{C}$ in the trailing-edge region, the variable strength of near-wake vortex shedding caused the flow-field fluctuations to be Reynolds-number and trailing-edge-geometry dependent. In the current experiments, vortex-shedding strength peaked at Re$_{C}{=}4{\times}10^{6}$ with the 56$^{\circ}$ bevel-angle trailing edge. A dimensionless scaling for this phenomenon constructed from the free-stream speed, the wake thickness, and an average suction-side shear-layer vorticity at the trailing edge collapses the vortex-shedding strength measurements for $1.4{\times}10^{6}{\le}{\it Re}_{C}{\le}50{\times}10^{6}$ from both trailing edges and from prior measurements on two-dimensional struts at Re$_{C}{\sim}2{\times}10^{6}$ with asymmetrical trailing edges.