/MONVOL/GAS

Block Format Keyword

/MONVOL/GAS - Perfect Gas

Description

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
Ascalet		AscaleP		AscaleS		AscaleA		AscaleD
				Trelax
Pext		Pini		Pmax		Vinc		Mini
Nvent

Define Nvent vent holes membranes (3 Lines per vent holes membrane)

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
surf_IDv	Avent				Ideleted
Tvent
fct_IDt	fct_IDP	fct_IDA		Fscalet		FscaleP		FscaleA

Field	Contents	SI Unit Example
monvol_ID	Monitored volume identifier (Integer, maximum 10 digits)
unit_ID	Optional unit identifier (Integer, maximum 10 digits)
monvol_title	Monitored volume title (Character, maximum 100 characters)
surf_IDex	External surface identifier (Comment 1) (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 (Comment 9) (Real)
Pext	External pressure (Real)
Pini	Initial pressure (Real)
Pmax	Maximum pressure (Comment 4) Default = 1030 (Real)
Vinc	Incompressible volume (Real)
Mini	Initial (gas) mass (Real)
Nvent	Number of vent holes (Integer)
surf_IDv	Vent holes membrane surface identifier (Comment 7) (Integer)
Avent	if surf_IDv ≠ 0: scale factor on surface Default = 1.0 (Real) if surf_IDv = 0: surface of vent holes 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)

1.	surf_IDex must be defined using segments associated with 4-nodes or 3-nodes shell elements (possibly void elements), and not with /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:

where, t is the time and ft is the function of fct_IDt.

where, P is the pressure and fP is the function of fct_IDP.

4.	When Pmax is reached, the pressure is reset to external pressure and venting has no effect.

5.	Vent hole membrane is deflated if T > Tvent or if the pressure exceeds Pdef while more than .

6.	vent_holes_surface =

Where,

A is the Area of surface surf_IDv

A0 is the initial Area of surface surf_IDv

fA is function of fct_IDA

fP is function of fct_IDP

Functions fP = fct_IDP are assumed to be equal to 1, if they are not specified (null identifier).

Function fA = fct_IDA is assumed as:

if it is not specified.

7.	If surf_IDv ≠ 0 (surf_IDv is defined).

vent_holes_surface =

If surf_IDv = 0 (surf_IDv is not defined).

vent_holes_surface =

Where, A is the Area of surface surf_IDv

fA is function of fct_IDA

ft is function of fct_IDt

fP is function of fct_IDP

Functions ft = fct_IDt and fP = fct_IDP are assumed to be equal to 1, if they are not specified (null identifier).

Function fA = fct_IDA is assumed as:

if it is not specified.

8.	For tire modeling, pressure in the tire is:

So, Pext and Pini have to be defined.

9.	Pressure will be applied linearly from Pext at time t=0 to Pini at time t=Trelax.