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.

Water entry is a complex nonlinear behavior that involves the multiphase flow coupling, which exists extensively in various engineering fields. In the present work, the shear stress transport k − ω turbulence model is imported to close the governing equations. The air–water interface and the six degree-of-freedom motion of the cylinder are defined using the volume of fluid method and the overlapping of grid technology, respectively. A three-dimensional numerical model to simulate the vertical water entry of cylinder under various wind and current velocities is carried out. The results generated from the unsteady dynamic characteristics of the flow field are verified against the published experimental data. A numerical parametric study is subsequently conducted to study in detail the effect of wind and current velocity on translational, rotational, and multipoint pressure characteristics in the process of water entry. The study from the evolution mechanism of cavity and the flow field revealed that the expansion speed and the closure mode of cavity change with the velocity of wind and current, which in turn affects the dynamic motion of cylinder over time and the complex distribution of pressure and velocity field and multiscale vortex structure in the process of water entry.