ALE and Fluid Structure Interaction in LS-DYNA

Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions. With an Eulerian-Lagrangian (fluid-structure) coupling algorithm, Eulerian parts may interact with Lagrangian parts in the same model. The Eulerian method is limited by dissipation and dispersion problems associated with the fluxing of mass across element boundaries. In addition, the Eulerian mesh must span the whole active space covering all Lagrangian structures and the spatial range of their motions. This requires a large mesh and thus high computing cost. The multi-material arbitrary Lagrangian-Eulerian (MMALE) method improves upon pure Eulerian formulation by allowing the reference fluid mesh(es) to translate, rotate and deform, thus minimize the amount of flux transport, and reduce mesh size of the reference fluid mesh(es).