/MONVOL/AIRBAG1

Block Format Keyword Describes one-chambered airbag with hybrid input of injected gas. This keyword is similar to /MONVOL/AIRBAG (Obsolete), but has more flexible input.

  • Gas materials specified in separate /MAT/GAS cards
  • Composition of injected gas mixture and injector properties specified in separate /PROP/INJECT1 or /PROP/INJECT2 cards

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/MONVOL/AIRBAG1/monvol_ID/unit_ID
monvol_title
surf_IDex   Hconv            
Ascalet AscaleP AscaleS AscaleA AscaleD
mat_ID   μ Pext T0 Iequil Ittf
For each injector
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
inject_ID sens_ID Ijet node_ID1 node_ID2 node_ID3        
Jetting function data (read only if Ijet = 1)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
fct_IDPt f c t _ I D P θ f c t _ I D P δ   FscalePt F s c a l e P θ F s c a l e P δ
Define Nvent vent holes and Nporsurf porous fabric surfaces
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Nvent Nporsurf                
For each vent hole
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
surf_IDv Iform Avent Bvent     vent_title
Tstart Tstop Δ P d e f Δ t P d e f   IdtPdef
fct_IDt fct_IDP fct_IDA   Fscalet FscaleP FscaleA
fct_IDt' fct_IDP' fct_IDA'   Fscalet' FscaleP' FscaleA'
Chemkin model data (read only if Iform =2)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
fct_IDv   Fscalev            
Insert for each porous surface
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
surf_IDps Iformps Iblockage           surface_title
Tstart Tstop Δ P d e f Δ t P d e f   IdtPdef
Insert only if Iformps =0
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Cps Areaps fct_IDcps fct_IDaps Fscalecps Fscaleaps
Chemkin model date (insert only if Iformps =2)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
fct_ID_psv   Fscale_psv            

Definition

Field Contents SI Unit Example
monvol_ID Monitored volume identifier.

(Integer, maximum 10 digits)

 
unit_ID Unit Identifier.

(Integer, maximum 10 digits)

 
monvol_title Monitored volume title.

(Character, maximum 100 characters)

 
surf_IDex External surface identifier.

(Integer)

 
Hconv Heat transfer coefficient. 17

(Real)

[ W m 2 K ]
Ascalet Abscissa scale factor for time-based functions.

Default = 1.0 (Real)

[ s ]
AscaleP Abscissa scale factor for pressure-based functions.

Default = 1.0 (Real)

[ Pa ]
AscaleS Abscissa scale factor for area-based functions.

Default = 1.0 (Real)

[ m 2 ]
AscaleA Abscissa scale factor for angle-based functions.

Default = 1.0 (Real)

[ rad ]
AscaleD Abscissa scale factor for distance-based functions.

Default = 1.0 (Real)

[ m ]
mat_ID Material identifier for initial gas (/MAT/GAS).

(Real)

 
μ Volumetric viscosity.

Default = 0.01 (Real)

 
Pext External pressure.

(Real)

[ Pa ]
T0 Initial temperature.

Default = 295K (Real)

[ K ]
Iequil Initial thermodynamic equilibrium flag.
= 0
The mass of gas initially filling the airbag is determined with respect to the volume at time zero.
= 1
The mass of gas initially filling the airbag is determined with respect to the volume at beginning of injection. 6

(Integer)

 
Ittf Time shift flag.
Active only when at least one injection sensor is specified. Determines time shift for venting and porosity options when injection starts at a Time to Fire specified in a sensor.
= 0 (Default)
=1 and 2
Obsolete.
=3
All options are shifted. 15

(Integer)

 
Njet Number of injectors.

(Integer)

 
inject_ID Injector property identifier.

(Integer)

 
sens_ID Sensor identifier.

(Integer)

 
Ijet Jetting flag.
= 0
No jetting.
= 1
Jetting.

(Integer)

 
node_ID1, node_ID2, node_ID3 Node identifiers N1, N2, and N3 for jet shape definition.

(Integer)

 
fct_IDPt If Ijet = 1: identifier of the function number defining Δ P ( t ) .

(Integer)

 
f c t _ I D P θ If Ijet = 1: identifier of the function number defining Δ P ( θ ) .

(Integer)

 
f c t _ I D P δ If Ijet = 1: identifier of the function number defining Δ P ( δ ) .

(Integer)

 
FscalePt If Ijet = 1: scale factor for fct_IDPt.

Default = 1.0 (Real)

[ Pa ]
F s c a l e P θ If Ijet = 1: scale factor for f c t _ I D P θ .

Default = 1.0 (Real)

[ Pa ]
F s c a l e P δ If Ijet = 1: scale factor for f c t _ I D P δ .

Default = 1.0 (Real)

[ Pa ]
Nvent Number of vent holes.

(Integer)

 
Nporsurf Number of porous surfaces.

(Integer)

 
surf_IDv Vent holes area surface identifier.

(Integer)

 
Iform Formulation flag.
= 0 (Default)
Set to 1.
= 1 (Default)
Isenthalpic.
= 2
Chemkin.
= 4
Isenthalpic with possible gas (mat_ID) flow-in.

(Integer)

 
Avent If surf_IDv ≠ 0: scale factor on vent hole area.

Default = 1.0 (Real)

 
If surf_IDv = 0: vent hole area.

Default = 0.0 (Real)

[ m 2 ]
Bvent If surf_IDv ≠ 0: scale factor on impacted vent hole area.

Default = 1.0 (Real)

 
If surf_IDv = 0: Bvent is reset to 0 for vent hole area.

Default = 0.0 (Real)

[ m 2 ]
vent_title Vent hole title.

(Character, maximum 20 characters)

 
Tstop Stop time for venting.

Default = 1030 (Real)

[ s ]
Tstart Start time for venting.

Default = 0 (Real)

[ s ]
Δ P d e f Pressure difference to open vent hole membrane.

Δ P d e f = P d e f P e x t

Default = 0 (Real)

[ Pa ]
Δ t P d e f Minimum duration pressure exceeds Pdef to open vent hole membrane.

Default = 0 (Real)

[ s ]
IdtPdef Time delay flag when Δ P d e f is reached:
= 0
Pressure should be over Δ P d e f during a Δ t P d e f cumulative time to activate venting.
= 1
Venting is activated Δ t P d e f after Δ P d e f is reached.

(Integer)

 
fct_IDt Porosity versus time function identifier.

(Integer)

 
fct_IDp Porosity versus pressure function identifier.

(Integer)

 
fct_IDA Porosity versus area function identifier.

(Integer)

 
Fscalet Scale factor for fct_IDt.

Default = 1.0 (Real)

 
FscaleP Scale factor for fct_IDp.

Default = 1.0 (Real)

 
FscaleA Scale factor for fct_IDA.

Default = 1.0 (Real)

 
f c t _ I D P δ If Ijet = 1: identifier of the function number defining Δ P ( δ ) .

(Integer)

 
FscalePt If Ijet = 1: scale factor for fct_IDPt.

Default = 1.0 (Real)

[ Pa ]
F s c a l e P θ If Ijet = 1: scale factor for f c t _ I D P θ .

Default = 1.0 (Real)

[ Pa ]
F s c a l e P δ If Ijet = 1: scale factor for f c t _ I D P δ .

Default = 1.0 (Real)

[ Pa ]
Nvent Number of vent holes.

(Integer)

 
fct_IDt' Porosity versus time function identifier during contact.

(Integer)

 
fct_IDP' Porosity versus pressure function identifier during contact.

(Integer)

 
fct_IDA' Porosity versus impacted surface function identifier during contact.

(Integer)

 
Fscalet' Scale factor for fct_IDt'.

Default = 1.0 (Real)

 
FscaleP' Scale factor for fct_IDP'.

Default = 1.0 (Real)

 
FscaleA' Scale factor for fct_IDA'.

Default = 1.0 (Real)

 
fct_IDv Outflow velocity function identifier (Chemkin model, only if Iform = 2).

(Integer)

 
Fscalev Scale factor on fct_IDv.

Default = 1.0 (Real)

[ m s ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaada Wcaaqaaiaab2gaaeaacaqGZbaaaaGaay5waiaaw2faaaaa@39DE@
surf_IDps Porous surface identifier (ignored if Iformps =0).

(Integer)

 
Iformps Porosity formulation.
= 0
Bernouilli (Wang & Nefske) (no dependence on fabric material).
= 1
Bernouilli (Wang & Nefske).
= 2
Chemkin.
= 3
Graefe.

(Integer)

 
Iblockage Block leakage flag, if contact (Iformps > 0).
= 0
No.
= 1
Yes.

(Integer)

 
surface_title Porous surface title.

(Character, maximum 20 characters)

 
Cps Scale factor on leakage area (Iformps =0).

(Real)

 
Areaps Leakage area (Iformps =0).

(Real)

[ m 2 ]
fct_IDcps Function identifier defining Cps(t), ignored if Cps is not equal to zero.

(Integer)

 
fct_IDaps Function identifier defining Areaps(P-Pext), ignored if Areaps is not equal to zero.

(Integer)

 
Fscalecps Scale factor for fct_IDcps.

Default = 1.0 (Real)

 
Fscaleaps Scale factor for fct_IDaps.

Default = 1.0 (Real)

[ m 2 ]
fct_ID_psv Outflow velocity function identifier (Chemkin model, only if Iformps = 2).

(Integer)

 
Fscale_psv Scale factor on fct_ID_psv.

Default = 1.0 (Real)

[ m s ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaada Wcaaqaaiaab2gaaeaacaqGZbaaaaGaay5waiaaw2faaaaa@39DE@

Comments

  1. The airbag external surface should be built only from 4- and 3-noded shell elements. The airbag external surface cannot be defined with /SURF/SEG, or with /SURF/SURF, if a sub-surface is defined in /SURF/SEG.
  2. The volume must be closed and the normals must be oriented outwards.
  3. Abscissa scale factors are used to transform abscissa units in airbag functions, for example:(1)
    F ( t ) = f t ( t Ascale t )
    Where,
    t MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@
    Time
    f t
    Function of fct_IDt
    (2)
    F ( P ) = f P ( P Ascale P )
    Where,
    P MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@
    Pressure
    f P
    Function of fct_IDP
    The options are obsolete. Normally, the curve scaling parameters are used instead.
  4. Pressure and temperature of external air and the initial pressure and temperature of air inside of airbag is set to Pext. and T0.
  5. Initial thermodynamic equilibrium is written at time zero (Iequil =0) or at beginning of jetting (Iequil =1), based on the following equation with respect to the volume at time zero, or the volume at beginning of jetting:(3)
    P ext V = R M 0 M i T 0
    Where,
    M 0 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamytamaaBa aaleaacaaIWaaabeaaaaa@37AE@
    Mass of gas initially filling the airbag
    M i MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamytamaaBa aaleaacaaIWaaabeaaaaa@37AE@
    Molar mass of the gas initially filling the airbag
    R MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@
    Gas constant depending on the units system given in /BEGIN card. For example in SI system:(4)
    R = 8.314 J mole K
  6. If jetting is used, an additional Δ P j e t pressure is applied to each element of the airbag:(5)
    Δ P jet = Δ P ( t ) Δ P ( θ ) Δ P ( δ ) max ( n · m , 0 )

    With m being the normalized vector between the projection of the center of the element upon segment (N1 and N3) and the center of the element; θ the angle between vectors MN2 and m (in degrees), δ the distance between the center of the element and its projection upon segment (N1 and N3).

    The projection of a point upon segment (N1 and N3) is defined as the projection of the point in direction MN2 upon the line (N1 and N3) if it lies inside the segment (N1 and N3). If this is not the case, the projection of the point upon segment (N1 and N3) is defined as the closest node N1 or N3.

    clip0087
    Figure 1. Dihedral Shape of the Jet

    with M between of N1 and N3

  7. If node_ID3 = 0, node_ID is set to node_ID1 and the dihedral shape is reduced to a conical shape.
  8. If fct_IDv = 0: isenthalpic outflow is assumed, else Chemkin model is used and outflow velocity is:(6)
    v = Fscale v f v ( P P ext )
    Where, f v is the function of fct_IDv.
    • Isenthalpic model

      Venting or the expulsion of gas from the volume is assumed to be isenthalpic.

      The flow is also assumed to be unshocked, coming from a large reservoir and through a small orifice with effective surface area, A.

      Conservation of enthalpy leads to velocity, u, at the vent hole. The Bernouilli equation is then written as:

      (monitored volume) γ γ 1 P ρ = γ γ 1 P ext ρ vent + u 2 2 (vent hole)

      Applying the adiabatic conditions:

      (monitored volume) P ρ γ = P ext ρ vent γ (vent hole)

      Where, P MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@ is the pressure of gas into the airbag and ρ is the density of gas into the airbag.

      Therefore, the exit velocity is given by:(7)
      u 2 = 2 γ γ 1 P ρ ( 1 ( P ext P ) γ 1 γ )

      For supersonic flows the outlet velocity is determined as described in Supersonic Outlet Flow in the Theory Manual.

      The mass out flow rate is given by:(8)
      m ˙ out = ρ vent · vent _ holes _ surface · u = ρ ( P ext P ) 1 γ · vent _ holes _ surface · u
      The energy flow rate is given by:(9)
      E ˙ out = m ˙ out E ρ V = ( P ext P ) 1 γ * vent _ holes _ surface * u E V

      Where, V MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@ is the airbag volume and E MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiDaaaa@36EF@ is the internal energy of gas into the airbag.

    • Chemkin model(10)
      m ˙ out = ρ vent _ holes _ surface f v ( P P ext ) Fscale v

      Where, ρ is the density of the gas within the airbag and f v is the function of fct_IDv.

  9. Vent hole area is computed as:(11)
    v e n t _ h o l e s _ a r e a   = A v e n t A n o n _ i m p a c t e d f t ( t ) f P ( P P e x t ) f A ( A n o n _ i m p a c t e d A 0 ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaaqaaaaaaaaa WdbiaadAhacaWGLbGaamOBaiaadshacaGGFbGaamiAaiaad+gacaWG SbGaamyzaiaadohacaGGFbGaamyyaiaadkhacaWGLbGaamyyaiaabc cacqGH9aqppaGaamyqamaaBaaaleaacaWG2bGaamyzaiaad6gacaWG 0baabeaakiabgwSixlaadgeadaWgaaWcbaGaamOBaiaad+gacaWGUb Gaai4xaiaadMgacaWGTbGaamiCaiaadggacaWGJbGaamiDaiaadwga caWGKbaabeaakiabgwSixlGacAgadaWgaaWcbaGaamiDaaqabaGcda qadaqaaiaadshaaiaawIcacaGLPaaacqGHflY1ciGGMbWaaSbaaSqa aiaadcfaaeqaaOWaaeWaaeaacaWGqbGaeyOeI0IaamiuamaaBaaale aacaWGLbGaamiEaiaadshaaeqaaaGccaGLOaGaayzkaaGaeyyXICTa ciOzamaaBaaaleaacaWGbbaabeaakmaabmaabaWaaSaaaeaacaWGbb WaaSbaaSqaaiaad6gacaWGVbGaamOBaiaac+facaWGPbGaamyBaiaa dchacaWGHbGaam4yaiaadshacaWGLbGaamizaaqabaaakeaacaWGbb WaaSbaaSqaaiaaicdaaeqaaaaaaOGaayjkaiaawMcaaaaa@7F75@
    + B vent A impacted f t ( t ) f P ( P P ext ) f A ( A impacted A 0 )
    With impacted surface:(12)
    A impacted = e S vent n c ( e ) n ( e ) A e
    and non-impacted surface:(13)
    A non _ impacted = e S vent ( 1 n c ( e ) n ( e ) ) A e

    Image12
    Figure 2.

    Where for each element e of the airbag materials n c ( e ) means the number of impacted nodes among the n ( e ) nodes defining the element and A e is the area of element e.

    And,

    A0 is the initial area of surface surf_IDv

    f t , f P and f A are functions of fct_IDt, fct_IDP and fct_IDA

    f t' , f P' and f A' are functions of fct_IDt', fct_IDP' and fct_IDA'

  10. Functions fct_IDt' and fct_IDP' are assumed to be equal to 1, if they are not specified (null identifier).
  11. If function fct_IDA' is not specified, it is assumed as:(14)
    f A ( A ) = A
  12. To account for contact blockage of vent holes and porous surface area, flag IBAG must be set to 1 in the correspondent interfaces (Line 3 of interface TYPE7 or TYPE23). If not, the nodes impacted into the interface are not considered as impacted nodes in the previous formula for Aimpacted and Anon_impacted.
  13. When there is no sensor which activates gas injection, the vent hole membrane is deflated, if time T becomes greater than the Tstart or if the pressure P exceeds Pdef value longer than the time given in Δ t P d e f .
  14. When at least one of the injectors is activated by the sensor, then the activation of venting and porosity options is controlled by Ittf

    Tinj is the time of the first injector to be activated by the sensor.

    Ittf = 0:

      Venting, Porosity
    Activation When P > Δ P d e f longer than the time Δ t P d e f , or T > T s t a r t
    Deactivation Tstop
    Time dependent functions No shift
    Ittf = 3:
      Venting, Porosity
    Activation When T > T i n j and P > Δ P d e f longer than the time Δ t P d e f , or T > T i n j + T s t a r t
    Deactivation T i n j + T s t o p
    Time dependent functions Shifted by T i n j + T s t a r t

    All other related curves are active when the corresponding venting, porosity or communication option is active.

    The variety of Ittf values comes from historical reasons. Values Ittf =1 and 2 are obsolete and should not be used. Usual values are Ittf =0 (no shift) or Ittf =3 (all relative options are shifted by Tinj).

  15. Leakage by porosity formulations; the mass flow rate flowing out is computed as:
    • Iformps = 0 m ˙ out = A eff 2 P ρ Q 1 γ γ γ 1 [ 1 Q γ 1 γ ] (Isentropic - Wang Nefske)

      with Q = P ext P

      and A eff = C ps Area ps or A eff = C ps ( t ) Area ps ( P P ext )

      C p s ( t ) is the function of fct_IDcps and Area p s ( P P e x t ) is function of fct_IDaps

      The effective venting area Aeff does not vary with different airbag fabric materials.

    • If Iformps > 0, the effective venting area Aeff is computed according to the input in the /LEAK/MAT input for fabric materials of TYPE19 or TYPE58.

      Iformps = 1 m ˙ out = A eff 2 P ρ Q 1 γ γ γ 1 [ 1 Q γ 1 γ ] (Isentropic - Wang Nefske)

      Iformps = 2 m ˙ out = A eff ρ v ( P P ext )

      Where, υ is the outflow gas velocity (Chemkin).

      Iformps = 3 m ˙ out = A eff 2 ρ ( P P ext ) (Graefe)

  16. If leakage blockage is activated, Iblockage=1, the effective venting area is modified as:(15)
    A eff = A non _ impacted

    Anon_impacted is non-impacted surface 11.

    The blockage will be active only if flag IBAG is set to 1 in the concerned contact interfaces (line 3 of interface TYPE7 and TYPE23).

  17. The lost heat flow is given by:(16)
    Q ˙ ( x , t ) = H conv Area ( x , t ) ( T ( x , t ) T 0 )