A Coupling of Empirical Explosive Blast Loads to ALE Air Domains in LS-DYNA

A coupling method recently implemented in LS-DYNA® allows empirical explosive blast loads to be applied to air domains treated with the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation. Previously, when simulating structures subjected to blast loads, two methods of analysis were available: a purely Lagrangian approach or one involving the ALE and Lagrangian formulations coupled with a fluid-structure interaction (FSI) algorithm. In the former, air blast pressure is computed with empirical equations and directly applied to Lagrangian elements of the structure. In the latter approach, the explosive as well as the air are explicitly modeled and the blast wave propagating through the ALE air domain impinges on the Lagrangian structure through FSI. Since the purely Lagrangian approach avoids modeling the air between the explosive and structure, a significant computational cost savings can be realized – especially so when large stand-off distances are considered. The shortcoming of the empirical blast equations is their inability to account for focusing or shadowing of the blast waves due to their interaction with structures which may intervene between the explosive and primary structure of interest. The new method presented here obviates modeling the explosive and air leading up the structure. Instead, only the air immediately surrounding the Lagrangian structures need be modeled with ALE, while effects of the far-field blast are applied to the outer face of that ALE air domain with the empirical blast equations; thus, focusing and shadowing effects can be accommodated yet computational costs are kept to a minimum. Comparison of the efficiency and accuracy of this new method with other approaches shows that the ability of LS-DYNA® to model a variety of new blast scenarios has been greatly extended.

application/pdf J-I-03.pdf — 362.2 KB