Simcenter Madymo How can I set up an airbag inflation simulation to determine the inflated volume of my airbag model?

If you have an airbag model in Simcenter Madymo for which you want to determine the inflated volume, you can do this in the following manner:

1. Apply a simple airbag inflator definition with a constant mass flow rate over time (you can use air as gas and a contact temperature equal to ambient gas temperature). See figure below.

2. Define hole outflow to ambient using HOLE.MODEL1 (defined under MATERIAL.HOLE), using a CDP_FUNC defined as a step function with the discharge pressure coefficient kept to zero below the over-pressure threshold and a high constant value (e.g. 10.0) starting from the applied over-pressure threshold (e.g. 0.1 bar = 0.1E+05 Pa). See figure below.

3. Make sure you have the OUTPUT_AIRBAG_CHAMBER defined with in it at least SELECT.VOLUME with WRITE_TOTAL=ON (note: for a multiple chamber airbag this should be done for all airbag chambers and outputted volumes need to be added to obtain total airbag volume). Also make sure you have requested for the defined airbag chamber output via AIRBAG_OUTPUT_LIST under TIME_HISTORY_FE in CONTROL_OUTPUT.
4. Run the simulation with sufficiently long duration (end time) to have the airbag inflated and its volume kept at a (near) constant value after the chosen over-pressure threshold is reached.

A simple example model with scaled generic 140 liter passenger airbag is attached to this article.
The zipfile includes both the Madymo input file (.xml) to run and a MADPost session file (.mps) to display results after simulation.
The example model uses Simcenter Madymo R2406 Solver and Workspace.

The model response (inflated airbag at end time, airbag gas pressure and airbag volume vs. time) is shown in figure below.