Water entry of sphere with porous hollow structure

Based on the numerical method of large eddy simulation, research on the cavity evolution and multiphase flow characteristics of porous hollow spheres is conducted. An experimental platform for hollow spheres is established, and numerical simulation results are compared with experimental data to verify the feasibility of the numerical method. The results indicate that, compared to hydrophilic solid spheres, significant cavities are generated during water entry. A clear jet phenomenon is formed in the central through-hole of the porous hollow sphere, and the internal jet presents a network shape and converges to the top position inside the porous hollow sphere. The hydrodynamic force coefficient of hollow spheres is smaller than that of solid spheres. As the initial velocity increases, the shape of the cavity gradually becomes more fluctuating, and the first peak value of the hydrodynamic force coefficient gradually increases. The smaller the initial velocity, the larger the second peak value of the porous hollow sphere after pinch-off. Increasing the diameter and hole diameter will significantly increase the peak value of the hydrodynamic force coefficient when impacting the water surface, while increasing the thickness and number of holes can increase the peak value of the hydrodynamic force coefficient after cavity collapse.