Water entry and exit of axisymmetric bodies by CFD approach

Abstract

The water impact and subsequent entry of three rigid axisymmetric bodies, a sphere and two cones, in the early phase are simulated using CFD utilizing a VOF scheme to track the free surface and the results compared with the recent experimental results available in the literature. The penetration depth, vertical velocity and vertical acceleration time histories have been reproduced well by CFD with a wide choice of mesh density, whereas the peak pressure on impact required a much finer mesh and appropriate choice of the time step. Delineating an interaction region around the trajectory of the body with fine mesh and an adaptive time stepping strategy has worked well to capture the peak impact pressure accurately with reasonable computational effort.The ‘full’ motion of the sphere, which is buoyant, has also been simulated using CFD allowing its 6-dof motion for several cycles of entry and exit phases. The features of the behavior, especially the loss of symmetry of the trajectory, are discussed. Keywords: CFD, Cone, Sphere, Water entry, Water impact