Analysis of Wave Force and Run-Up Acting on an Impermeable Vertical Circular Cylinder Surrounded by Multiple Thick Porous Layers

In this work, we analyze the effect of multiple thick porous layers, fitted around a rigid vertical circular cylinder, on the wave forces acting on the rigid structure. Using the eigenfunction expansion method in cylindrical coordinates, we derive the expressions for velocity potentials in the respective domains and finally calculate the wave force acting on the rigid structure by integrating the pressure term. Consideration of the multiple porous layers, each with different porosities, gives rise to a very basic question to answer: what will be the appropriate arrangement of the porous layers to reduce the wave impact? Hence, for numerical study, we consider three different arrangements of the porous layers. For such arrangements of the porous layers, we also analyze the effects of the other crucial parameters, such as the number and the thickness of the porous layers, on the wave force. The key finding of the analysis is that the wave force acting on the rigid structure can be minimized by increasing the number of porous layers with decreasing porosity from the innermost layer to the outermost layer. The wave breaking and forced oscillations for certain values of the porous impedance parameter are some of the interesting observations. The present model is also verified against an existing work in the literature which shows an excellent agreement.