Enhancements and validation of FPM fluid structure interaction module applied to curtain airbag deployment

Models to represent in position situations based upon uniform pressure assumptions are well established and have been used extensively in the automotive industry for more than 15 years. More recently, in the beginning of the year 2000, advanced simulation techniques with Fluid Structure Interaction (FSI) approaches, such as VPS-PAMCRASH/FPM (Finite Point Method) have been introduced in the development of airbag restraint systems. Their main fields of application are Out Of Position (OOP) situations, where the occupant is close to the airbag casing. For these load cases the deployment kinematics of the airbag and local associated pressures play a major role and require modeling precisely the gas flow. Similarly these techniques are used for side airbags like curtain airbags or knee bags where the deployment kinematics are highly dependent upon local pressures on the membrane of the airbag.

The turbulence and viscous flow effects cannot be neglected for curtain bags. It will be shown in this paper that neglecting these effects leads to possible bad prediction of the deployment kinematics.

ESI, ITWM and VW have conducted a joint program to extend FPM to turbulent viscous flow simulation, which improves simulation based design also for this category of airbags. The steps of this methodology project will be presented from the academic and scientific work led by ITWM for the introduction and the validation of the k-epsilon turbulence model in FPM to the industrial cases on airbag deployments.