Development and Validation of an ALE-Based Airbag Simulation Methodology

For the past fifteen years, automotive safety engineers have mainly relied on the Control Volume (CV) approach to simulate airbag deployment. The CV approach assumes that the gas is uniformly distributed in an inflated bag and therefore the airbag fabric is subject to uniform pressure. This assumption is true only when the airbag is fully deployed, and therefore makes CV approach inappropriate for Out-of-Position (OOP) safety analysis in which an occupant is in close proximity to the air bag module when it deploys, and therefore airbag-occupant interaction occurs before the bag is fully inflated. This paper describes the theory and validation of a new airbag simulation tool, an ALE-based (Arbitrary-Lagrange-Eulerian) approach. This tool, developed by Livermore Software Technology Corporation (LSTC), is aimed at using ALE as a CFD (Computational Fluid Dynamics) tool to model the gas flow inside a deploying airbag and the interaction between the airbag and the inflator gas. The validation of this methodology is performed through comparing the simulation results with test results of various test setup and airbag design.