AbstractVertical wall breakwater with culvert (VWBC) is an environmentally friendly way proposed for the encircled harbor basin, which can break waves and allow the current to pass through. This paper adopts a theoretical analysis combining physical experiments and computational fluid dynamics (CFD) numerical simulations to study the hydrodynamic performance of the VWBC and to propose an optimal culvert for engineering applications. Based on a linear wave theory, theoretical analysis demonstrates the interaction between waves and the VWBC through the matched eigenfunction expansion method. The effects of the structural parameters (culvert and rubble mound foundation) on the hydrodynamic performances, such as the wave transmission coefficient (berthing stability), wave force (structure stability), and oscillatory flow (water exchange) inside the culvert are taken into consideration. Newly designed physical experiments and CFD numerical simulations are performed to verify the correctness of the theoretical analysis and to reveal the nonlinear characteristics of the wave transmission and oscillatory flow. It is found that the berthing stability and water exchange are mainly affected by the length and height of the culvert as well as the rubble mound foundation, and a total transport flow toward the harbor basin will be produced with an increase in wave height. Furthermore, the optimal culvert is obtained through the theoretical analysis. With the optimal culvert, VWBC can improve the berthing and structure stability, further promote the water exchange, and enhance the environment in the harbor basin.