Axisymmetric gravity wave diffraction by flexible porous cylinder system in two-layer fluid

The present study deals with the hydroelastic analysis of axisymmetric gravity wave interaction with concentric flexible porous cylinder systems in two-layer fluid having a free surface and an interface in water of finite depth. The cylinder system consists of a rigid cylinder and an outer flexible porous cylinder. Both the cases of complete and partial cylinders such as bottom-standing and surface-piercing partial cylinders are considered. The mathematical problem is handled using a generalized orthogonal relation suitable for two-layer fluid along with the least squares approximation method. Further, the role of flexible porous cylinder in attenuating wave forces on the rigid cylinder is analyzed in various cases. The effectiveness of the cylinder systems in trapping surface waves are analyzed from the numerical results in different cases by analyzing the reflection coefficients, wave elevations in surface and internal modes, deflection of the flexible porous outer cylinder under wave action and wave forces acting on both the inner and outer cylinders. The study reveals that full wave reflections in surface and internal modes occur when the annular distance between the cylinders is approximately an integer multiple of half of the wave length and the phenomenon is independent of the barrier configurations.