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Highlights: [•] Interaction between the flow and net cages is simulated using an iterative scheme. [•] Flow through a net cage is studied considering the fluid–structure interaction. [•] Application of the present numerical approach to multiple net cages is presented. [Copyright &y& Elsevier]

Abstract: A three-dimensional (3D) numerical model is established to simulate the flow field around fishing plane nets in a current. The realizable k–ε turbulence model was chosen to describe the flow, and the governing equations are solved by using the finite volume method. In this model, the net is modeled using the porous media model. The unknown porous coefficients are determined from the hydrodynamic forces on the net and from the flow velocities and the attack angles using the least squares method. In order to validate the numerical model, the numerical results were compared with the data obtained from two physical model tests. The comparisons show that the numerical results are in good agreement with the experimental data. This numerical model is applicable for the simulation of the flow field around a fishing net. Using the proposed method, this paper presents the flow field around a plane net with different plane net inclination angles, plane net heights, spacing distances between two plane nets and plane net numbers. This study provides information about the flow field around the fishing net cage. [Copyright &y& Elsevier]

Abstract: In our previous research, the hydrodynamic behavior of a two-dimensional (2D) plane fishing net in current was simulated. Based on the research, a model of a three-dimensional (3D) net is established by using the lumped mass method. To verify the validity of the numerical model, model test results by other authors are cited and compared with the numerical results. The simulated results are in good agreement with experimental ones. In this paper, the 3D net model is applied to investigate the effects of structure size ratio (RDH) and mesh type on the 3D net deformation of the gravity cage in current. The numerical results indicate that the decrease of RDH is practically feasible in improving the cage net deformation. With a sinker system the net deformation with diamond mesh is greater than that with square mesh. When the bottom-collar sinker system is applied, with an increase in current velocity, the net deformation with diamond mesh is less than with square mesh. The results of this study provide a better understanding of the hydrodynamic behavior of the gravity cage. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to investigate the shape and tension distribution of fishing nets in current. A numerical model is developed, based on lumped mass method to simplify the net. The motion equation is set up for each lumped mass. The Runge–Kutta–Verner fifth-order and sixth-order method is used to solve these simultaneous equations, and then the displacement and tension of each lumped mass are obtained. In order to verify the validity of the numerical method, model tests have been carried out. The results by the numerical simulation agree well with the experimental data. [Copyright &y& Elsevier]

In the present work, the hydrodynamic characteristics of full-scale rectangular otter board were studied by numerical simulation, including the effects of aspect ratios (AR), flow distribution around the otter board, induced velocity, induced angle of attack (AOA), effective AOA and induced drag coefficient. It was demonstrated that the otter board had a critical AOA of 40° (when the stall appeared) and induced AOA of 3~10°. The maximum induced drag coefficient was 0.185, which is a great contribution to the total drag coefficient. The otter board exhibited better performance when the AR was set to 0.5, and higher AR had a smaller critical AOA (the stall happened earlier). The maximum lift coefficient decreased with an increasing AR, while the maximum lift-to-drag ratio increased. The induced drag coefficients showed similar trends across ARs, initially rising with an increase of the AOA, and then dropping. The flow distribution around the otter board showed that the wing-tip vortex was fully developed at the AOA of 40°, and the AR can affect the development of the wing-tip vortex. [ABSTRACT FROM AUTHOR]