An explicit Lagrangian approach for 3D simulation of fluid-structure-interaction problems

A Lagrangian fully explicit approach for the co-simulation of three-dimensional problems of Fluid-Structure Interaction (FSI) is here presented. The fluid domain is modelled as a weakly compressible material through an explicit version of the Particle Finite Element Method (PFEM). The structure is modelled with standard FEM through the commercial software Abaqus/Explicit. The strong coupling of the partitioned approach is ensured by the Gravouil and Combescure (GC) algorithm. The GC scheme allows for the use of incompatible space-time discretizations in the two subdomains. The coupling problem leads to a small explicit system of decoupled equations when conforming meshes are used at the interface, while, in the case of non-conforming meshes, a weakly coupled system is obtained. A novel and efficient mesh smoothing procedure is proposed to remove bad quality tetrahedra that may arise in the frequent remeshing framework of the PFEM, since they can lead to an overly small stable time step size. The fully Lagrangian description of the present method is particularly effective in problems characterized by strong variations in the fluid boundaries. Moreover, the highly parallelizable and fully explicit nature of the equations of the global solver is appealing for real-scale engineering applications with fast dynamics and/or a high degree of non-linearity.