Three-dimensional numerical simulation of cavity dynamics of a stone with different spinning velocities

Abstract

To investigate the complex cavity evolution, hydrodynamic action and motion response of a stone impacting on the water, a calculation model is established with six degrees of freedom. The Large Eddy Simulation (LES) model is used to solve the turbulence based on Computational Fluid Mechanics (CFD). The accuracy of the numerical model is verified by comparing the numerical results with experimental results. The stone is released above the free surface with different initial spinning velocities under a certain attack angle. The cavity dynamics, including the dome, open cavity and splash, are investigated during the impact process. Asymmetric impact cavity and the rotation around the y-axis are discovered. And the factors caused the rotation are analyzed. In particularly, there is a special cavity flow phenomenon found by the simulation that obvious tortuosity appears between first cavity and second cavity for a certain spinning velocity. Moreover, the hydrodynamic action, trajectory and reduce rate of velocity are studied for different spinning velocities. Compared to the non-spinning stone, the pressure distribution for the stone with spinning velocity is no longer regular and symmetrical. The maximum value of the pressure at the initial moment of the impact increases with increasing spinning velocity. The results demonstrate that the deviation in z-axis also increases with increasing spinning velocity. Furthermore, the trajectory of the stone with higher spinning velocity shows a more apparent bend in the o-xy plane. In the primary stage of impact, the spinning velocity of the stone decreases at a faster rate for the stone has a higher initial spinning velocity. Then, a transient increase of the reduce rate appears for the stone with violent tumble.