Semi-analytical study of wave interaction with a submerged permeable sphere applied on a spherical aquaculture cage. (15th March 2023)

• Record Type: Journal Article
• Authors: Gharechae, Ataollah; Ketabdari, Mohammad Javad
• Is Part Of: Ocean engineering. Volume 272(2023)
• Publication Date: 2023-03-15
• Subjects: Porous sphere -- Aquapod cage -- Wave force -- Added mass and damping -- Hydrodynamic coefficients -- Water particle velocities; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2023.113839
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Spherical aquaculture cages are a technology of marine fish farming recently developed for installation in offshore areas. In harsh sea conditions, the cage can be temporarily fully immersed and safe from the intense loads. This paper studied semi-analytically linear waves incident to a submerged permeable sphere. The primary purpose of this research is to study the wave excitation forces, hydrodynamic coefficients, and wave strength inside the sphere. The problem's governing equations were established in the context of potential flow theory, considering two inner and outer regions and using multiple methods and Darcy's law for flow passing the porous media. The developed method was applied to the Aquapod spherical cage with a radius of a = 9.0 m. The results indicate that the porosity parameter causes wave excitation forces and added mass decreases, but the damping coefficient increases significantly in the particular range of wavenumbers. Moreover, the peak value of the wave excitation force, damping coefficient, and the average of water particle velocities inside the cage occurs at k a = 0.5, where k is the wavenumber. Also, at enough immersion, the damping coefficient is independent of depth. The results of this research are helpful in better understanding the behavior of spherical aquaculture cages in submergence conditions. Highlights: Waves incident to the Aquapod spherical aquaculture cage are analyzed semi-analytically. Using Darcy's law, a porous sphere is modeled by dipole distribution on permeable boundaries. At sufficient immersion of a porous sphere, the damping coefficient is independent of depth with a peak value of 0.3. The peak value of wave force occurs at k a ∼ 0.5 . For G 0 ≥ 2 and k a > 1, the average amplitude of the normalized water particle velocities inside the cage is larger than 0.8.