Wave diffraction from a vertical cylinder with two uniform columns and porous outer wall

Based on a linens model of the pressure difference between two sides of a p orous wall and the fluid velocity inside it, an analytic solution is establ ished for wave diffraction from a cylinder with an outer pore us column and an Inner solid column. Numerical experiments are carried out to examine th e effects of the wave force on a porous low-column cylinder and the wave el evations outside and inside the cylinder due to the pore us character of th e outer column and the ratio between the radii of the inner and outer colum ns. The numerical results show that the increase in the coefficient of poro sity of the outer column of a double column cylinder will reduce the wave e levation around the cylinder and the wave load on it. The radius of the inn er column does not affect too much the wave elevation around the cylinder a nd the total force on the cylinder.