Hydrodynamic performance of a new stepped perforated wave absorbing and wave force reducing structure

• A new stepped perforated wave absorbing and wave force reducing structure is proposed. • The new stepped perforated structure can remarkably reduce wave transmission coefficient and wave impact force. • The porosity of each step is the main factor affecting the wave absorbing and wave force reducing effect of the new structure. • An empirical formula for estimating the transmission coefficient of the new structure under different wave conditions is proposed. Breakwaters are widely used as offshore protection structures for harbors, anchorages, and marinas. However, a lower wave transmission coefficient typically corresponds to larger wave forces on the structure, which increases stability requirements and construction costs. The present study proposes a novel stepped perforated structure composed of three layers of staggered porous baffles designed to dissipate wave energy while simultaneously reducing wave forces. The effect of key geometric parameters on both wave energy dissipation and force reduction were investigated through numerical simulations and flume experiments. The results demonstrate that the proposed structure effectively attenuates incident waves while reducing the horizontal wave force F t . Compared with traditional perforated vertical walls, the proposed structure reduces F t by more than 20% at the same wave transmission coefficient K t . The porosities of the three baffle layers significantly influence both K t and F t : increasing the second ( S 2 ) and third ( S 3 ) porosities leads to larger K t and smaller F t , whereas the first porosity ( S 1 ) exhibits a critical threshold beyond which K t increases after an initial decrease. Furthermore, the adaptability of the recommended stepped perforated configuration under different wave conditions was assessed, and an empirical formula for estimating K t under different wave conditions was proposed. The proposed structure may provide a promising wave-absorbing and force-reducing solution for the design of coastal and offshore breakwaters.