Cavity evolution and response of a hollow structure during oblique high-speed water entry

A two-way fluid-structure interaction method is used to investigate the cavity evolution, trajectory, and motion characteristics of a hollow cylinder during oblique high-speed water entry. The finite volume method is used to handle the fluid domain, and the finite element method is used to handle the structural domain. Meanwhile, key data from the two computational domains are exchanged during each iteration process to achieve fluid-structure coupling simulation. The results indicate that a jet forms in the middle of the hollow cylinder, which will deflect and eventually collide toward the upstream side of the cavity. Due to the obstruction of the internal jet, the water entry angle of the hollow cylinder changes less than that of a completely sealed hollow cylinder. Compared to the completely sealed hollow cylinder, the completely open hollow cylinder has significantly smaller deformation and strain energy during water entry, resulting in better stability and durability. As the initial velocity increases, the displacement, fluid force, and stress of the completely open hollow cylinder all increase. As the initial water entry angle increases, the stress and strain energy at a specific angle (45°) are smaller than those of a completely sealed hollow cylinder. As the diameter increases, the stress and strain energy experienced by the completely open hollow cylinder gradually increase. As the thickness increases, the force and stress acting on the completely open hollow cylinder increase. As the length increases, the trajectory of the hollow cylinder becomes closer to a straight line.