Airbag Fabric Porosity
Porosity of airbag material is modeled by the addition of a porosity card /LEAK/MAT to /MAT/LAW58 card.
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/MAT/LAW58/1
Altair test fabric law58
# Init. dens. Ref. dens.
8E-7 0
# E1 B1 E2 B2 FLEX
0.380 0 0.380 0 1.0
# G0 GT AlphaT Sensor
0.0035 0.0055 7.175 1
# Df Ds Gfrot ZeroStress
0 0 0 1
# N1 N2 S1 S2
1 1 0 0
# Dir 1
500 1.00
# Dir 2
501 1.00
# Dir12
502 1.00
# FCT_ID4 FCT_ID5 Fscale4 Fscale5 FCT_ID6 Fscale6
600 600 1 1 502 1
/LEAK/MAT/1
Fabric
# Ileak AscaleT AscaleP
1
# AC' fct_IDAC’
# LC AC
1.0e-03 1.0e-03
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The /LEAK/MAT specifies how the effective porous area of a component having this material will vary as a function time or pressure. It is determined by the value of Ileakage.
Ileakage =1:
Ileakage =2:
Ileakage =3:
Ileakage =4:
Ileakage =5:
Where, and are the stretches in warp and weft directions and is the angle between warp and weft directions.
Ileakage =6:
with and .
Parts with this material are considered porous, when referenced via a surface ID using the /MONVOL/FVMBAG1 surf_IDps option.
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/MONVOL/FVMBAG1/1
DAB
# Isur
4
# Scal_T Scal_P Scal_S Scal_A Scal_D
0 0 0 0 0
# Mat_ID Mu Pext Tphi Iequi Ittf
4 0.1 0.00010135 0 0 3
# Njet
1
# Inj_ID Isensor surf_IDinj
10 1 100
# Nvent Nps
0 1
#Sur_id_ps Iform_ps
4 1
# Tstart Tstop dPdef DtPdef ldtpdef
….
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- Iformps = 1 (Isentropic - Wang Nefske)
- Iformps = 2
Where, v is the outflow gas velocity (Chemkin)
- Iformps = 3 (Graefe)
