Wave diffraction and radiation problems on a heteroaxial floating structure composed of two cylinders

Abstract

To expand the application of the analytical method in dealing with the diffraction and radiation problems of the heteroaxial cylinder structure under waves, this paper takes the heteroaxial cylinder structure composed of two cylinders as an example to establish an analytical model. The wave diffraction and radiation problems of the structure were solved, and the wave force, added mass and radiation damping coefficients of the structure were obtained. The respective cylindrical coordinate systems were established in the axis of the upper and lower cylinders, and the water area was divided into three regions. Analytical solution of velocity potentials in different regions of wave diffraction and radiation problems are derived by using matched eigenfunction expansion method (MEEM) and Fourier series expansion method. After comparing with the boundary element method (BEM) software, the effect of the relative distance between the upper- and lower-cylindrical axes on the wave force and hydrodynamic coefficients of the structure were analyzed, and the effect of the height ratio of the upper- and lower-cylinder was discussed. The results show that different from coaxial structure, the wave exciting force of heteroaxial floating structure composed of two cylinders may have two peaks with the variation of wave number. The peak values of hydrodynamic coefficients A11, A22, B11 and B22 increase with the height ratio.