Fully nonlinear investigation of focused wave slamming on a freely rotating flap

Abstract This paper concerns the focused wave slamming induced by a freely rotating flap using domain-decomposition higher-order boundary element method (HOBEM) with fully nonlinear conditions through which the process of jet detaching from body is successfully captured. The stable results of splash jet are obtained through linearly-varying-potential hypothesis. The time derivative of velocity potential on the body surface is calculated through the auxiliary function method, and the strong mutual dependence between the flap and the fluid flow is further decoupled accordingly. The non-uniform mesh scheme is adopted in the computational domain to guarantee both efficiency and accuracy, i.e., using fine meshes in the slamming region with strong nonlinearity. The abilities of present model to generate the focused wave and simulate wave slamming on a rotating flap, are respectively, verified. Relatively comprehensive parametric studies are performed, and the results based on flap's motion states, free surface profiles and pressure distributions point out the effects of frequency bandwidth, focused position, input wave amplitude, water depth and phase angle on the slamming specifically. It has been found the slamming occurs before wave groups focus completely and focused trough further enlarges the slamming pressure compared with focused crest.