Modelling Open Ocean Aquaculture Structures Using CFD and a Simulation-Based Screen Force Model

Abstract

The numerical framework of the open source CFD solver REEF3D is utilised to study the fluid–structure interaction of an open ocean aquaculture system and waves. The presence of the net is considered in the momentum equations of the fluid using a forcing term based on Lagrangian–Eulerian coupling and the hydrodynamic loads on the net. They are defined semi-empirically using a screen force model. Here, the hydrodynamic force coefficients are calculated from the net geometry and fluid velocity. The necessary force coefficients are predicted from a new simulation-based screen force model. Here, CFD simulations are performed to obtain the hydrodynamic loads on net panels for varying net geometries, angles of attack and velocities. Then, a Kriging metamodel is applied to fit a polynomial to the data. The proposed net model is validated against measurements for waves and current through rigid net panels and applied to simulate the dynamics of an open ocean aquaculture cage in waves. In current, the model predicts the drag forces and velocity reduction within a 10% error band, whereas it tends to under-predict the lift forces by up to 20%. In waves, the model tends to over-predict the crests with increasing wave height, but the deviations are also within a 10% error band.