Oblique water-entry of non-axisymmetric bodies at varying speed by a fully nonlinear method

The hydrodynamic problem of non-axisymmetric bodies entering a water surface at varying speed has been analysed by three-dimensional (3D) incompressible velocity potential theory. All the boundaries are updated in a stretched coordinate system by a time-stepping method. The fully nonlinear boundary conditions are satisfied at the moving free surface and the body surface boundary through an improved Eulerian form. In particular, the free surface elevation and potential variation are traced at a given azimuth in each theta plane of the cylindrical coordinate system, to overcome the numerical difficulties caused by the complex variation of the 3D curved free surface. Remeshing and smoothing are applied regularly along the line between the free surface and each theta plane. A Detailed convergence study with respect to time step and element size has been undertaken and high accuracy has been achieved. Simulations are made for axisymmetric and non-axisymmetric bodies at various manners of water entry. Comparisons are made between constant and varying speed entries, between vertical and oblique entries, and detailed results are provided and discussed.