The fluid mechanics of splashing bow waves on ships: A hybrid BEM-SPH analysis

The free surface bow flow around a fast and fine ship in calm water is studied with an emphasis on generation and evolution of the breaking and splashing bow wave using the 2D þ t theory. A temporal domain-decomposition strategy is adopted which combines sequentially two Lagrangian methods: a potential-flow solution, given by a boundary element method (BEM), follows the jet evolution up to the breaking and then initiates a rotational solution, provided by a smoothed particle hydrodynamics (SPH) technique. The latter describes the splashing and the evolution of rotational flow structures generated during the evolution. The compound method is very efficient and proved to be able to capture the breaking features. A validation has been performed through comparison with experimental data and other numerical solutions available in the literature. The DDG51 vessel is used to carry on a parameter investigation in terms of the ship speed (Froude number) and surface tension. The analysis confirms a substantial influence of the Froude number on the patterned morphology and highlights the importance of surface tension for small-scale ships (e.g. small-scale models tested in towing tanks) in inhibiting the jet formation and evolution.