Issues in ALE simulation of airbags

Abstract

Airbag simulations have emerged as an important means to study their efficiency in occupant safety. The situation in which the occupant deviates from the nominal position is commonly referred to as an out-of-position (OOP) situation. The focus in this paper is on developing simulation models that can be used for OOP studies in the future. To capture the initial stages of inflation of the airbag in OOP simulations, the focus has now shifted towards discretizing the fluid flow inside the airbag using the Arbitrary Lagrangian Eulerian (ALE) approach. The interaction between the fluid (Eulerian mesh) and the structural elements (Lagrangian mesh) is defined through a coupling. In this work, a description of the process for generating the mesh for the folded airbag is presented. Some strategies adopted to resolve penetration and time step issues in folding have been highlighted. The folded airbag is inflated in simulation using both the CV (Control Volume) and ALE approach, and the results are compared. For validation, the inflation of the airbag was recorded using high-speed photography and a tank test conducted to characterise the inflator. The performance of the ALE method and CV method for the purpose of OOP simulations is compared with the experimental observations.