Suppression of the hydroelastic responses of a composite very large floating structure by a submerged elastic ring

With the aid of the method of matched eigenfunction expansions, the hydroelastic dynamics of a composite very large floating structure on a two-layer fluid is analytically investigated in the framework of linear potential flow theory. The composite structure consists of a semi-immersed rigid cylinder fixed with a floating elastic ring and protected by a submerged flexible ring for mitigating the hydroelastic responses. A new dispersion relation for the hydroelastic waves in the two-layer fluid containing a submerged plate is derived to obtain the wave numbers with a given frequency. The coupling effect among the oscillation of rigid cylinder, the deformation of the floating and submerged plates and the motion of wave is considered by dividing the problem into scattering and radiation parts. An inner product is introduced to deduce the unknown expansion coefficients of the velocity potentials. The amplitudes of heave and pitch motions for the rigid cylinder are obtained and shown graphically. The effects of the physical parameters are explored to confirm the mitigative effect of the submerged ring on the response of the composite very large floating structure. A submerged porous ring can also eliminate the amplitudes of waves in the surrounding water region.