/MONVOL/GAS
Block Format Keyword Describes the perfect gas monitored volume type.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/MONVOL/GAS/monvol_ID/unit_ID | |||||||||
monvol_title | |||||||||
surf_IDex | I_equi | ||||||||
Ascalet | AscaleP | AscaleS | AscaleA | AscaleD | |||||
Trelax | Tini | ||||||||
Pext | Pini | Pmax | Vinc | Mini | |||||
Nvent |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
surf_IDv | Avent | Ideleted | |||||||
Tvent | |||||||||
fct_IDt | fct_IDP | fct_IDA | Fscalet | FscaleP | FscaleA |
Definitions
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. 1 (Integer) |
|
I_equi | Thermodynamic equilibrium
flag. 3
(Integer) |
|
Ascalet | Abscissa scale factor for
time based functions. Default = 1.0 (Real) |
|
AscaleP | Abscissa scale factor for
pressure based functions. Default = 1.0 (Real) |
|
AscaleS | Abscissa scale factor for
area based functions. Default = 1.0 (Real) |
|
AscaleA | Abscissa scale factor for
angle based functions. Default = 1.0 (Real) |
|
AscaleD | Abscissa scale factor for
distance based functions. Default = 1.0 (Real) |
|
Ratio of specific
heat. (Real)
|
||
Volumetric
viscosity. Default = 0.01 (Real) |
||
Trelax | Relaxation time. 10 (Real) |
|
Tini | Initial
temperature. Default = 295K (Real) |
|
Initial mass density
inside the monitored volume. (Real) |
||
Pext | External
pressure. (Real) |
|
Pini | Initial
pressure. (Real) |
|
Pmax | Maximum pressure. 5 Default = 1030 (Real) |
|
Vinc | Incompressible
volume. (Real) |
|
Mini | Initial (gas)
mass. (Real) |
|
Nvent | Number of vent
holes. (Integer) |
|
surf_IDv | Vent holes area surface
identifier. 8 (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) |
||
Ideleted | if surf_IDv ≠ 0 if Ideleted = 0: area of surface surf_IDv is considered for venting |
|
if
Ideleted =
1: area of deleted elements inside surface surf_IDv is considered for
venting. (Integer) |
||
Tvent | Start time for
venting. Default = 0.0 (Real) |
|
Pressure difference to
open vent hole membrane
. (Real) |
||
Minimum duration pressure
exceeds Pdef to
open vent hole membrane. (Real) |
||
fct_IDt | Porosity vs time function
identifier. (Integer) |
|
fct_IDP | Porosity vs pressure
function identifier. (Integer) |
|
fct_IDA | Porosity vs 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) |
Comments
- surf_IDex must be defined using segments associated with 4-nodes or 3-nodes shell elements (possibly void elements), and not with /SURF/SEG.
- The volume must be closed and the normals must be oriented outwards.
- By default, I_equi =0 assumes that the volume to be filled by the gas will not increase. If the volume increases, the Pext pressure will not be reached. If the volume increases when inflated, use I_equi =1 or 2 and define the initial temperature and initial gas density.
- Abscissa scale factors are used to
transform abscissa units in airbag functions, for example:
(1) where, t is the time and is the function of fct_IDt.(2) Where, is the pressure and is the function of fct_IDP.
- When Pmax is reached, the pressure is reset to external pressure and venting has no effect.
- Vent hole membrane is deflated if T > Tvent or if the pressure exceeds Pdef while more than .
- vent_holes_surface =
Where,
- A
- Area of surface surf_IDv
- A0
- initial Area of surface surf_IDv
- Function of fct_IDA
- Function of fct_IDP
Functions = fct_IDP are assumed to be equal to 1, if they are not specified (null identifier).
Function fct_IDA is assumed as: if it is not specified.
- If surf_IDv ≠ 0 (surf_IDv is defined) the vent hole area is
computed as:
vent_holes_area =
If surf_IDv = 0 (surf_IDv is not defined).
vent_holes_area =
Where,- A
- Area of surface surf_IDv
- Function of fct_IDA
- Function of fct_IDt
- Function of fct_IDP
Functions = fct_IDt and = fct_IDP are assumed to be equal to 1, if they are not specified (null identifier).
Function = fct_IDA is assumed as:
if it is not specified.
- For tire modeling, pressure in the
tire is:
(3) So, Pext and Pini have to be defined.
- Pressure will be applied linearly from Pext at time t=0 to Pini at time t=Trelax.