LLM and X-FEM based interface modeling of fluid-thin structure interactions on a non-interface-fitted mesh

This paper presents a non-interface-fitted mesh method for fluid-thin structure interactions. The key components are the Lagrangian Lagrange-multiplier (LLM) method and the extended finite element method (X-FEM). The LLM couples fluid and thin structure through the Lagrangian nodes of the structure element. The X-FEM gives flow discontinuity to the fluid elements intersected by the structure element. The combination method is verified through applications to flow with a domain-partitioning boundary and flow-induced flapping of a flexible filament. We discuss how the discontinuities at the interface enhance the simulation results, how the lack of the discontinuities affects the results, and identify some effects of these discontinuity enrichments.