Application of ALE to nonlinear wave diffraction by a non-wall-sided structure

Abstract

Interactions between water waves and non-wall-sided structures are an-alyzed based on fully nonlinear potential theory. Arbitrary Lagrangian Eulerian (ALE) formulation is used for tracing markers on free surface as well as wave-body intersections. The feature of ALE is that complex mesh is generated only once at the beginning and fluid marker is moved along prescribed path at all other time steps. Since the prescribed path for each marker is equidistantly arranged, at any instant, the relative posi-tions of adjacent markers are well maintained, and thus good mesh qual-ity can be guaranteed throughout the computation. In order to trace the exact wave-body intersections i.e. waterline, the marker (intersection) is enforced to move along cross section line of body surface, which can take into account complex body geometry above still waterline. In the computation, HOBEM and 4th-order Runge-Kutta method are adopted as initial boundary value problem (IBVP) solver. For improving compu-tational efficiency, the total velocity potential is split into incident wave component and disturbed one. In this paper, we focus on diffraction of nonlinear waves by non-wall-sided structures. As a validation, we firstly study the diffracted waves by a circular cylinder. And then, the cases that circular cylinders with different flares are studied. To prove capacity of current scheme, nonlinear wave diffraction by ship geometry is also studied and by comparison with our experiment, pronounced agreement is achieved.