Water wave interaction with a bottom-standing surface-piercing porous compound coaxial cylinder

The concept of the integration of offshore wind power and ocean ranch represents a development trend of intensive use of the sea. With the rise of this concept, this paper proposes a new type of porous marine structure. Based on the assumptions of the linearized theory of water waves, the wave diffraction and radiation problems of the bottom-standing surface-piercing porous compound coaxial cylinder are studied in this paper. Two seabed conditions are considered: (a) the ideal state, where the seabed is impermeable, and (b) the actual state, where the seabed is porous. The analytical models for the hydrodynamic problems of the porous cylinder placed on the impermeable and porous seabed are established. The wave diffraction and radiation problems are solved by using the eigenfunction expansion method and the velocity potentials of the fluid motion are derived. To verify the correctness of the program, the present model is reduced and compared with existing models. After completing the verification, the effects of the porous seabed and structural parameters on the hydrodynamic characteristics of the porous cylinder are studied. The results indicate that the porous seabed has effects on the wave run-up on the porous cylinder, and the higher the seabed porous effect parameter, the smaller the wave run-up on the porous cylindrical surface of the outer cylinder and the impermeable cylindrical surface of the inner cylinder. Enlarging the porous effect parameter and the radius ratio of the compound cylinder leads to decreases in the wave force, moment, added mass, and radiation damping. By changing the parameters of the porous cylinder, the hydrodynamic characteristics of the porous cylinder can be greatly reduced. This study is expected to provide support for engineering design of relevant marine structures. © 2024 Author(s).