Wave diffraction from a truncated cylinder with a moonpool of arbitrary cross-section: A semi-analytical study

In this paper, a semi-analytical model is proposed to solve the diffraction problem from a cylinder with a moonpool. The cylinder and the moonpool can be in arbitrary shapes. Linear potential flow theory and eigenfunction matching method are adopted in the analytical model. After dividing the fluid domain into three regions (i.e., the region beneath the cylinder; the inner region enclosed by the cylinder; the exterior region outer the cylinder), diffracted spatial potentials in each region can be expressed by a series of eigenfunctions. The continuity conditions between adjacent regions together with a Fourier series method combined with the eigenfunction matching method are employed to determine the unknown coefficients in the expressions of diffracted potentials. The well-known potential of incident waves and the obtained diffracted potentials are then used to directly compute the wave excitation forces/moments acting on the cylinder and the wave excitation volume flux. Analytical results of wave excitation forces/moments and volume flux are compared with the numerical results obtained by using a boundary element method numerical solver. Wave diffraction from the cases with different shapes of either cylinder hull or moonpool is finally tested with the semi-analytical model.