Interaction of Water Waves with a Semiporous Bottom-Mounted Cylindrical Storage Tank Containing a Cylindrical Pile

In this study, we discuss the diffraction of linear water waves by a cylindrical storage tank whose inner part contains a cylindrical pile and the outer part contains a coaxial thin hollow porous cylinder in finite ocean depth. Here we consider two cases: (i) an impermeable solid circular cylinder surrounded by an outer coaxial thin hollow porous cylinder of the same height extending from the free surface to the seabed; (ii) a similar structure fully placed atop an impermeable solid circular cylinder with the same radius as the outer cylinder. The fluid region is divided into two subdomains and the separation of variables technique is used to obtain the analytical expressions for the corresponding potentials in each region. The porous wall condition is used with respect to the thin porous wall. Appropriate matching conditions are applied at the interface of the fluid subdomains to obtain a system of linear equations for the unknown coefficients which is solved. By considering different sets of values of the radius and the porosity of the cylinder, the hydrodynamic force and wave run-up are evaluated. It is observed that the wave forces and wave run-up get reduced on the inner cylinder corresponding to higher radius ratio and lower porosity whereas the wave forces on the outer cylinder get reduced for higher porosity. A suitable combination of the parameter values of the cylinder is likely to bring down the wave forces to a large extent. Upon verification and validation of results for both models against available analytical result and experimental data, it may be considered beneficial to apply the present models to certain applications in ocean engineering.