Rigid body motion response of closed fish farm in waves are simulated using OpenFoam with the extension module for fluid-rigid body coupling "FloatStepper"
The added mass instability problem is a numerical problem that arises for rigid body motion in incompressible fluid when the added mass is larger than the mass of the body. This can be mitigated by using an outer corrector loop on the body acceleration and fluid pressure. This becomes computationally expensive since each outer iteration involves a full CFD update of the fluid state. Instead, a non-iterative algorithm (FloatStepper) is available (Roenby J, Aliyar S, Bredmose H., 2024 A robust algorithm for computational floating body dynamics. R. Soc. Open Sci. 11:231453. https://doi.org/10.1098/rsos.231453). The purpose of the algorithm is to remove the added mass instability problem. cDynamics demonstrate the capability of the algorithm on a 2D closed fish farm (hemisphere). In this case, the mass of the body is much less than the added mass, which is more or less equal to the mass of the enclosed water volume.
