Semi-analytical study of linear waves interaction with a vertical permeable cylinder of arbitrary cross-section based on perturbation theory

Abstract

ABSTRACT This paper studies linear waves incident to a vertical permeable cylinder with arbitrary cross-section based on the boundary element method and perturbation theory. Considering a near-zero thickness for the permeable media, and using Darcy's law, the governing equation for the wave incident to a porous circular cylinder is derived based on the boundary element method. Then using perturbation theory and considering a small parameter ε denoting the variation of cylinder radius from circular ones, the corresponding equations were expanded for non-circular cylinders. The developed method was applied to ellipse-shaped and rectangular cylinders. The wave forces and the wave strength inside the cylinder under a variety of parameters such as wavenumber, and porosity parameter were studied. One application of these research results is a better understanding of the behaviour of non-circular aquaculture cages in sea waves. According to the results, near-trapped modes can occur inside rectangular cages with small porosity parameters.