Structural and hydrodynamic characteristics of hollow cylinder during high-speed water entry

The hollow cylinder is a special cylindrical body with a through structure in the middle position. A collaborative method based on the finite volume method and the finite element method is used to numerically calculate high-speed vertical water entry of the hollow cylinder. The results show that the hollow cylinder exhibits a unique internal jet phenomenon, and the height of the jet shows an almost linear growth trend. Compared to the completely sealed hollow cylinder, the displacement and velocity of the hollow cylinder after entering into water are greater, but the volume of generated cavities is smaller. The force and stress at the bottom of the hollow cylinder are smaller than those at the bottom of the completely sealed hollow cylinder. The force and stress at the bottom of the hollow cylinder are greater than those at its top position. The greater thickness of the hollow cylinder has greater velocity and displacement, as well as greater peak values of the force and stress at its bottom position. The stress fluctuation at the bottom of the hollow cylinder with a smaller thickness is more pronounced.