LS-DYNA ALE Nodal Coupling

LS-DYNA ALE solver has been used extensively on modeling fluid and gas behaviors. The accompanying FSI solver has been successfully applied on series of engineering problems such as tank sloshing, tire hydroplaning, bottle dropping, HE blasting, etc. The FSI solver, invoked by the *CONSTRAINED_LAGRANGE_IN_SOLID card, is intended to couple between ALE fluid elements and Lagrange structure segments. The LS-DYNA Discrete Elements recently developed has been successfully simulating sand undertaking explosion shockwaves from land mine detonations. In such models, sand is modeled as a group of discrete rigid particles. The pressure wave propagates in the sand through the penalty springs between discrete sand particles. The land mine is modeled by *MAT_HE using ALE multi-material element formulation. However, the existing FSI package can not handle the coupling between the ALE high explosives and sand particles as the FSI algorithm is segment based. This means that the Lagrange structure has to be a set of segments. The new nodal based coupling was developed so that the interaction between ALE fluids and node-based discrete elements could be resolved. The constraint-based coupling algorithm was implemented as the first phase of the development. The keyword is named *ALE_COUPLING_NODAL_CONSTRAINT. It has a similar input format and parameter list as the *CONSTRAINED_LAGRANGE_IN_SOLID card. Preliminary studies of method effectiveness have been done through an in-house land mine blast problem. The results agreed well with empirical data obtained through *LOAD_BLAST_ENHANCED.