Numerical investigation of water wave impacts on partially submerged perforated semi-circular structures

Abstract

Wave impacts, prevalent in engineering, pose significant threats to coastal and offshore structures. Investigating their effects on diverse structures offers insights into the underlying mechanisms, which enhances engineering applications. This paper focuses on the overall characteristics of wave slamming on partially submerged perforated semi-circular structures, emphasizing the temporal and spatial characteristics of impact pressure, air entrapment, and the influence of porosity, focusing instead on qualitative insights rather than quantitative analysis of the relationship between wave parameters and loads. A two-phase flow model, incorporating the Volume of Fluid (VOF) method and accounting for air compressibility, was utilized. Structures with different porosity were studied. The incident wave condition was the 2nd-order Stokes wave, with a maximum structural height-to-water depth ratio of 0.529 in front of the structures. Numerical results indicate that pressure distribution on the structures can be categorized into four zones: the impact zone, the quasi-hydrostatic zone, the slightly affected zone, and the strongly fluctuated zone. The maximum pressure occurs in the vicinity of the still water level, and in most cases, this maximum pressure point is slightly below the still water level. The trapped air pocket between the wave surface and the structure can induce pressure oscillations. Conversely, air bubbles entrained in the water and air trapped within the perforated structures exhibit less significant effects. Structures with large openings exhibit a triangular pressure-time curve during a single impact cycle, whereas those with small openings show a more prominent quasi-hydrostatic component.