Dynamical Modeling and Numerical Simulation of Water Discharge Process of Spherical Objects

The process of an object leaping out of the water is very similar to the jumping process of an aquatic animal during prey or avoid predators. The study of the process of an object leaping out of the water is beneficial to the design of robots jumping out of water. In this work, the free jump of a sphere out of the water is successfully simulated based on the Computational Fluid Dynamics (CFD) software Fluent, with User-Defined Functions to control the motion of the sphere, the volume of Fluid model, dynamic meshing, and Detached Eddy Simulation. The velocity of the sphere at the water-air interface and the height of the sphere leaping out from the water surface obtained from the numerical simulation are compared with experimental results. The maximum error between the experimental and the simulated results is 2.28% in the water-discharge velocity and 2.65% in the leaping height from the water surface. In addition, this paper model the dynamics of the sphere during the water discharge process. The paper also analyses the free deformation of water surface, the water film rupture process on the surface of the sphere, the variation of fluid drag on the sphere, and the variation of the fluid velocity field during the free ascent of the sphere after acquiring an initial velocity of 2.81 m/s.