Semi-analytical study on regular sea wave interaction with circular elastic floaters of aquaculture fish cages

Abstract

In this paper, a semi-analytical model was developed to find the vertical motions and wavefield around elastic circular floaters of aquaculture fish cages in regular waves. The fluid is assumed inviscid, incompressible, and irrotational flow. A regular train of deep water waves was incident to a floater, which consist of two tori of high-density polyethylene (HDPE) pipes. The problem was analyzed with the assumption of the relatively large incident wavelength in comparison to the cross-section of tori. Slender body theory and matched asymptotic expansions were used with the inner solution close to the body section composed of suitable radiation solution at large distance of floater by distributing source and doublet along centerlines of floater constituent tori. In this approach, the fundamental solutions were developed for symmetric and anti-symmetric motions. Then, the governing equations on diffraction and incident waves were decomposed to Fourier modes of these solutions. The main influence parameters on vertical accelerations such as floater dimensions, wave number, the distances between tori, and bending stiffness of floater were studied. The model results demonstrate good agreement with those of the BEM. Furthermore, the Energy Transmission Index (ETI) was introduced for describing the effect of the floater on the downstream environment.