Numerical Simulation of Hydrodynamics Around Net Meshes Using REEF3D

Hydrodynamics and turbulence around net meshes have drawn more and more attention because it is closely related to forces on the structures and safety issues of offshore fish farms. In terms of numerical modeling of forces on nets, Morison or screen force model is ordinarily adopted to account for its hydrodynamics. However, these methodologies mainly rely on empirical experimental or cylindrical hydrodynamic coefficients, neglecting flow interactions between adjacent cruciforms or net bars. In this study, REEF3D open-source hydrodynamic toolbox is adopted to analyze flow around net meshes explicitly and investigate the hydrodynamics related to forces on the structure. The simulation accuracy is in good agreement with flume experiments and previous research. Flow velocity and vorticity around net bars and knots are investigated. The results demonstrate that 2 × 2 or 3 × 3 mesh cases are more reliable when studying turbulence around net meshes, flow interactions around adjacent net bars, knots should be taken into consideration. Two patterns to control Sn, one is to change the diameter of net bars and the other is to control length, have different effects on the flow around meshes. This paper presents a first step in the aim to derive a new empirical formula for Cd depending on Sn, and Re, which are more related to the physics in offshore conditions.