A robust PFEM-LS/FEM partitioned coupling framework for 3D fluid-structure interaction

Simulating solids subjected to complex, flow-induced loads remains a major challenge in fields such as aerospace, turbomachinery, and biomechanics. These scenarios often involve intricate Fluid-Structure Interactions (FSI) characterized by free surface flows, large deformations, thermo-mechanical interaction, strong coupling effects, solid-solid contact and material rupture, phenomena that conventional simulation approaches struggle to capture with accuracy. In such cases, using simplified boundary conditions to model fluid effect on the solid surface is inadequate. To address these limitations, we present a robust, fully partitioned coupling framework that integrates a Particle Finite Element Method with Level Set-based remeshing (PFEM-LS) fluid solver and a Finite Element Method (FEM) structural solver. Strong coupling is enforced via a Dirichlet-Neumann strategy, where equilibrium between fluid and structure is iteratively achieved at each time step using an Interface Quasi-Newton (IQN) method with (truncated) Multi-Vector Jacobian (MVJ) updates. The IQN-MVJ is combined with a dimensionality reduction technique based on a truncated Singular Value Decomposition (SVD) to decrease computation time on large-scale simulations. Boundary data transfer across non-conformal fluid and solid meshes is handled through Radial Basis Function (RBF) interpolation, enabling independent and adaptive mesh refinement on both sides of the interface. The framework’s robustness is demonstrated through validation against established 2D and 3D benchmarks as well as newly developed test cases.