Physical investigation of transient dynamic behaviors of cavitation-induced vibration over a flexible hydrofoil

Abstract

The unsteady flow characteristics of cavitation often cause adverse effects such as vibration, noise, and erosion. With the application of new materials, the vibration and deformation of hydrofoils are increasingly obvious, and the fluid–structure interaction becomes very important. In this paper, the cavitating flow fields of a NACA 66 rigid hydrofoil and flexible hydrofoil are numerically studied. The hydroelasticity of the flexible hydrofoil is implemented by using a fluid–structure interaction method under a tight-coupling strategy. The Schnerr–Sauer model is used to describe the cavitation process, and the turbulence is resolved by the large eddy simulation method. The finite element method is used to calculate the structural deformation. Compared with the rigid hydrofoil, the flexible hydrofoil exhibits smaller and more diffuse areas of cavitation. This is because the hydrofoil hydroelasticity inhibits the development of cavitation and causes larger amplitude and more intense pressure pulsations. In addition, the hydroelasticity increases the vorticity and the flow field becomes more complex. Analysis of the turbulence characteristics of the wake flow field show that the flexible hydrofoil creates more intense turbulence and a wider velocity pulsation area in the direction of incoming flow. Finally, using dynamic mode decomposition to capture the flow field modal characteristics, we find that the energy of the flexible hydrofoil is mainly concentrated in the first two modes, producing a larger coherent structure, while the high-frequency modes contain less energy.