Coupling of Potential Flow and CFD Model for Fluid and Structure Interactions

Abstract Computational Fluid Dynamics (CFD) tools are widely used to simulate wave and structure interactions in marine & offshore industry. However, conventional CFD tools require significant computational resources. This is largely due to the requirement of large computational domain to ensure adequate development of nonlinear wave evolutions as well as to avoid boundary effects resulting from wave interacting with any fixed or floating structures in the domain. Furthermore, very fine mesh elements are required to avoid excessive numerical dissipation during wave propagation. All of these factors will significantly increase the computational costs, resulting in the conventional CFD approaches being impractical for simulations of wave-structure interactions over a long duration. In this paper, a coupled potential flow and CFD model is developed to reduce the simulation cost. The model decomposes the simulation domain into far-field and near-field region. Wave propagation in the far-field region is simulated by a potential flow solver (High-Order Spectral or HOS method), while the wave-structure interactions in the near-field region are simulated by a fully nonlinear, viscous, and two-phase CFD solver (Star-CCM+). A forcing zone is distributed between the two regions to blend the computational outputs from the potential flow into the CFD solvers. The coupling algorithm has been developed to improve the accuracy and efficiency. The coupled solver is applied to simulate two cases, namely regular wave propagation, and regular wave interaction with a vertical cylinder. Finally, a simulation of a 3D wave encountering an FPSO (Floating Production Storage and Offloading) is presented.