Wave radiation from multiple cylinders of arbitrary cross sections

A semi-analytic model based on linear potential theory is developed to solve wave radiation from an array of truncated cylinders with arbitrary cross sections, free to oscillate independently in water of finite depth. The radiated velocity potential in the interior region below each cylinder and the exterior region extending to infinity are expressed as a series of eigenfunctions in the local cylindrical coordinate system using the method of separation of variables. They are solved subsequently by imposing the continuity condition of the velocity and pressure at the wetted surfaces of the cylinders and the fluid interfaces between adjacent regions. In the process, the Fourier series expansion method is applied to the terms regarding the arbitrary cross sections. The model is successfully validated through a case study with two caissons – excellent agreement is obtained with a numerical model based on the boundary element method. The semi-analytic model is then applied to explore the influence of layout (angle and spacing between the two caissons) on the added-mass and radiation damping coefficients. It is found that the hydrodynamic interaction between the two caissons can increase or decrease the value of the coefficients depending on the wave frequency.