Experimental investigation on vertical water-entry cavity of sphere

Experimental investigations and analysis were carried out on the vertical water-entry of the spheres. The development process of the cavities induced by the vertical water-entry of the spheres was discussed including the formation, open, closure and collapse of the cavities. The influences of the water-entry velocities and surface conditions of the spheres on the cavities were experimentally obtained. And the displacements, velocities, accelerations and drag coefficients of the spheres during the water entry were analyzed. The investigated results show that the motion parameters of the spheres present highly nonlinear characteristics. And there are obvious fluctuations of the motion parameters and the drag coefficients during the closed-cavity phase if the water-entry velocities are high.