The airbag simulation used by Radioss uses a special uniform pressure airbag. Hence, regardless of state of inflation or shape, the pressure remains uniform.

Perfect gas law and adiabatic conditions are assumed. Injected mass and temperature are defined as a time function. A sensor can define the inflater starting time.

Deflation of vent hole is available after reaching a pressure ( P d e f ) for a given duration Δ t P d e f or at time ( T d e f ) criteria. Δ t P d e f prevents deflation due to initial peak of pressure corresponding to the jetting activation.

Figure 1. Uniform Pressure Airbag
The key assumptions are:
  • Uniform airbag pressure MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyi1HSnaaa@3852@ kinetic energy is negligible
  • Adiabatic conditions
The airbag simulation must include:
  • Injection of energy and mass
  • Bag mechanics (i.e. unfolding, expansion, membrane tension, impacts ...)
  • Exhaust through vent holes