LES study of unsteady cavitation characteristics of a 3-D hydrofoil with wavy leading edge

The present study seeks to conduct numerical investigations of the cavitating flow characteristics around a sinusoidal wavy leading edge (WLE) 3-D hydrofoil underlying a NACA 63(4) -021 profile with an aspect ratio of 4.3. Cavitational and non-cavitational characteristics of hydrofoils are numerically examined at a chord-based Reynolds number of 7.2 x 10(5) . The sinusoidal leading edge geometries include two WLE amplitudes of 5% and 25% and two WLE wavelengths of 25% and 50% of the mean chord length. We examined the cavitating flow around the hydrofoils in different cavitation numbers, namely sigma = 0.8 and sigma = 1.2. The flow over the protuberances of the WLE hydrofoil is considered at varying chord lengths and a constant angle of attack alpha = 6 degrees, where significant spanwise variations in all flow properties, in contrast to the straight leading edge (SLE) hydrofoil, were observed. Large eddy simulation (LES) and Kunz mass transfer models are employed to simulate the dynamic and unsteady behavior of the cavitating flow. Besides, the compressive volume of fluid (VOF) method is used to track the cavity interface. Simulation is performed under the two-phase flow solver -interPhaseChangeFoam- of the OpenFOAM package. Compared to the SLE hydrofoil, we provided an exhaustive report of the time-averaged and instantaneous fluid dynamic characteristics of the cavitating flow around the sinusoidal leading edge hydrofoil, i.e., pressure, velocity, and vorticity fields, as well as lift and drag coefficients, and turbulent kinetic energy are reported. Furthermore, detailed analyses of the instantaneous cavity leading edge and flow separation treatment, vortical structure of the flow, vorticity stretching and dilatation, details of the spanwise flow, the formation of a low-pressure zone behind the WLE hydrofoil, streamwise velocity fluctuation, and evolution of the cavity dynamics through a complete cycle are reported. Results show that early development of the laminar separation bubble (LSBs) on the suction side of WLE hydrofoil prevents significant flow separation. Furthermore, the WLE cases exhibit a significantly reduced level of unsteady fluctuations in aerodynamic forces at the frequency of periodic vortex shedding. (C) 2020 Elsevier Ltd. All rights reserved.