Interaction between free surface flow and moving bodies with a dynamic mesh and interface geometric reconstruction approach

To investigate the fluid-rigid body interaction issues with free surfaces, a numerical approach has been developed. This algorithm is in an arbitrary Lagrangian–Eulerian description and Volume of Fluid (VOF) framework, using dynamic unstructured mesh to solve the coupled system. The fluid–solid interface uses partitioned Dirichlet–Neumann iterations with Aitken's relaxation. For the two-phase fluids part, an interface geometric reconstruction approach has been applied to accurately capture the free surfaces. This piecewise linear interface calculation (PLIC) based method uses Newton's iteration to efficiently reconstruct interfaces on an unstructured mesh, and applies an un-split scheme to transport variables. The algorithm has been successfully implemented in open source code OpenFOAM®, and was compared with the latter's built-in solver using interface compression method to deal with free surfaces. Numerical results suggest that our solver has better accuracy on multiphase flow problems, while the previous solver fails to obtain correct interfaces. Moreover, the capacity of accurately solving fluid-rigid body interaction problems with free surfaces has been achieved. Validation cases are provided for fluid–structure interaction problems with and without free surfaces, and results are in accordance with analytical and experimental data from the literature. The algorithm and solver in this paper, can be applied on fluid–structure interaction cases with free surfaces in the future, such as sloshing and water entry problems.