Dynamic Mesh Handling in Openfoam Applied to Fluid-structure Interaction Simulations

The power of OpenFOAM [1] in physical modelling stems from mimicking of partial differential equations in software, thus allowing rapid and reliable implementation of complex physical models. State-of-the art complex geometry handling and dynamic mesh features are essential for practical engineering use. This paper describes features of dynamic mesh support in OpenFOAM. Polyhedral mesh handling implemented in OpenFOAM is a flexible basis for its dynamic mesh features, at several levels. For simple cases of linear deformation or solid body motion, algebraic expressions suffice. For complex cases of time-varying geometry [2] or solution dependent motion, mesh deformation is obtained by solving a mesh motion equation. For extreme deformation, automatic motion is combined with topological changes, where the number or points, faces or cells in the mesh or its connectivity changes during the simulation. Finally, in cases of extreme and arbitrary mesh motion tetrahedral re-meshing based on edge swapping may be used. Examples of dynamic mesh handling with progressively complex requirements shall be used to show how object-oriented programming simplifies the use of dynamic mesh features with various physics solvers. A self-contained Fluid-Structure Interaction (FSI) solver in OpenFOAM acts as an illustration of dynamic meshing features and parallelised surface data transfer tools. It combines a second-order Finite Volume fluid flow solver with moving mesh support coupled to a large deformation formulation of the structural mechanics equations in an updated Lagrangian form [3].