A case study of numerical simulation on the interaction among random double caisson breakwater and seabed

This paper presents a case study of a double caisson composite breakwater in the Dongjiakou Port area of Qingdao Port's Hujia Mountain operation zone using the numerical model within the framework of OpenFOAM, considering random wave-structure-seabed interactions. The hydrodynamics and soil responses around the breakwater were solved using the Finite Volume Method (FVM) with appropriate boundary conditions. The JONSWAP spectra was used for the generation of random waves. The validations of the flow and seabed models and the coupling process were conducted by comparing with existing experimental data in literature. The influence of wave randomness on the wave-breakwater-seabed interactions was investigated by comparing the results between random waves and regular waves with same representative wave characteristics. Numerical results reveal that although random waves generally induce smaller time-varying responses than regular waves, occasional "spike"values occur, significantly surpassing those induced by regular waves. Specifically, maximum wave height in front of breakwater is 134% of the regular wave height, maximum pore pressures at the seabed surface increases by 31.6%. The distribution of soil responses show similar trend, but the maximum values are larger for random waves, with a difference up to 42.1%. Four designs of wave wall were proposed. It is found that the arc-shaped wave wall with a protrusion at the top corner of the caisson provides complete wave blocking, achieving a zero overtopping rate under the given wave conditions.