Development of a simulation model to determine stresses in steel wire net cage structures of fish farms

Abstract Adverse environmental conditions in water bodies, such as currents and waves, can be very stressful for net cage structures of fish farms. This work aims to develop a simulation model that can qualitatively estimate the mechanical loads in the wires of net cage segments of specific fish farms due to current influences. To set up the model, flow measurements were carried out in a wind tunnel on net cage surfaces with different wire diameters and mesh sizes. Different flow angles were tested. These measurements were validated by flow simulations in Ansys CFX. In order to minimize the simulation time, the net cage surfaces of the aquaculture systems were replaced by porous media. Functions for drag and lift coefficients as well as velocity reduction factors were derived from the flow simulations in dependence on porosity and angle of attack. A fluid-structure interaction was performed by transferring these functions to a beam-node model created with Ansys APDL representing the entire aquaculture facility. The simulation model makes it possible to qualitatively determine the mechanical stresses in the individual wires of the net cage surfaces. The findings on the most stressed areas can be used to optimize the design of the aquaculture systems in detail using the submodel technology.