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.

High-speed visualization of vortical cavitation using synchrotron radiation

“…The distinct forms of vortical cavitation possible to emerge in various engineering applications have been categorized by (Arndt 2002). The development, temporal evolution and collapse of either or a combination of the aforementioned forms of vortex cavitation has been extensively investigated by experimental means in reference to shear flows (O'Hern 1990), as well as two-phase separated flows in clearance passages (Boulon et al 1999), over hydrofoils (Coutier-Delgosha et al 2007;Bourgoyne et al 2005) and past bluff bodies, e.g. spheres (Brandner et al 2010).…”

“…spheres (Brandner et al 2010). Periodic vorticalcavity shedding in the wake of a hydrofoil has been demonstrated to be enhanced by the vertical velocity fluctuations, which provide the perturbation necessary to trigger a Kelvin-Helmholtz instability responsible for the vortex rollup (Bourgoyne et al 2005). A method of specifying the distinct deformation mode of a stationary tip-vortex cavity has been proposed by Pennings et al (2015).…”

Control of Boundary Layer Separation and the Wake of an Airfoil using ns-DBD Plasma Actuators

“…More explicit investigation into the low-frequency regime is required to substantiate the claim of impulse-like behavior. Analysis of hot wire data at varying streamwise locations closer to the trailing edge (similar to that of Bourgoyne 2005) and excitation of the ns-DBD with a single pulse at F + ≤ 0.15 will help to further characterize this regime.…”

Numerical Investigation on Vortex Shedding from a Hydrofoil with a Beveled Trailing Edge

“…Bourgoyne et al [6,7] experimentally investigated the dominant features of flows over a two-dimensional (2D) hydrofoil with an antisinging trailing edge at Reynolds numbers ranging from 10 6 to 5 × 10 7 . They concluded that turbulent fluctuations in the near wake are Reynoldsnumber dependent because of the varying strengths of the structured near-wake vortex shedding.…”