Study on the cavity dynamics of water entry for horizontal objects with different geometrical shapes

The influence of geometrical shapes on cavity evolution, flow fields and vortex structures evolution during water entry processes are investigated by experimental and numerical methods in this paper. The cavity evolution for water entry of four horizontal objects with different geometrical shapes are captured by high-speed photography. The experimental results indicate that although the geometrical shape has influence on cavity shape and size, the pinch-off depths are very close for the open cavity cases. In the numerical study, a compressible two-phase flow solver combing with large eddy simulation (LES) and dynamic overset mesh based on OpenFOAM® platform is adopted to observe the cavity dynamics, flow fields and vortex structures information. Numerical results reveal that the cavity produced by the object with trapezoid section expand at a relatively higher speed in the radial direction to form a larger cavity due to the more kinetic energy transference to the fluid. The vorticity evolution shows that for the object with circle section, the vortex structures alternately shed at the cavity tail shortly after the cavity separates from the free surface. However, for the object with trapezoid section, the cavity is squashed distorted due to the hydrostatic pressure without alternating vortex shedding.