MONVOL

Bulk Data Entry Defines a one-chamber gas filled structure with hybrid input of inflated gas in explicit dynamic analysis or a cavity filled with fluid in implicit large displacement analysis.

Attention: Valid for Explicit Analysis only

Format


(1)	(2)	(3)	(4)
MONVOL	`MID`		`UNIT`
	`SURF`	`SID`
	`AMBIENT`	`PATM`	`TATM`

Optional continuation line to define properties of the initial gas inside the structure (for explicit analysis only. Implicit analysis ignores this line of data).


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
	`IAIR`	`PAIR`	`TAIR`
		`XMAIR`	`Cpa_air`	`Cpb_air`	`Cpc_air`	`Cpd_air`	`Cpe_air`

Optional continuation line to define a vent hole. It can be repeated as required (for explicit analysis only. Implicit analysis ignores this line of data).


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	`VENT`	`SIDV`	`C23`	`LCTC23`	`LCPC23`	`PDEF`

Optional continuation line to define properties of the injected gas. It can be repeated as required (for explicit analysis only. Implicit analysis ignores this line of data).


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	`MATGAS`	`LCM`	`LCT`
		`XM`	$C p a$	$C p b$	$C p c$	$C p d$	$C p e$

Optional continuation line to define properties of the incompressible/compressible fluid (for implicit large displacement analysis only. Explicit analysis ignores this line of data).


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	`HYDRA`	`BULK`

Optional continuation line to define properties of the ideal gas. (for implicit large displacement analysis only. Explicit analysis ignores this line of data).


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	`IAIR`	`PAIR`

Example


(1)	(2)	(3)	(4)	(5)	(6)
MONVOL	1
	`SURF`	10
	`AMBIENT`	1.013E5	293.0
	`MATGAS`	3	4
		0.004	40.0	0.0	0.0
	`IAIR`	1.013E5	293.0
		0.028	28.0	0.0	0.0

Description


Field	Contents	SI Unit Example
`MID`	Monitor volume identification number. No default (Integer > 0)
`UNIT`	Unit system. 0 (Default) kg-mm-ms-K 1 kg-m-s-K (SI units) 2 ton-mm-s-K
`SURF`	Flag to indicate the external surface of enclosed volume.
`SID`	External surface identification defined by a set of elements. No default (Integer > 0)
`ATM`	Flag to indicate that the two following fields define atmospheric pressure and temperature.
`TATM`	Ambient temperature. Default=293 K (Real ≥ 0.0)
`PATM`	Ambient pressure. Default=1 atm (Real ≥ 0.0)
`VENT`	Flag to indicate that the following five fields indicate the vent hole properties.
`SIDV`	Vent hole area surface identification number. No default (Integer > 0)
`C23`	Scale factor on vent hole area. Default=1.0 (Real > 0.0)
`LCTC23`	Curve defining vent hole coefficient as a function of time. No default (Integer > 0)
`LCPC23`	Curve defining vent hole coefficient as a function of pressure. No default (Integer > 0)
`PDEF`	Pressure difference between interior and ambient pressure to open vent hole. Default=0.0
`MATGAS`	Flag to indicate that the following four fields define the inflated gas properties.
`LCM`	Table that defines mass flow rate curve for the gas component.
`LCT`	Table that defines temperature curve for the gas component.
`XM`	Molar mass of the gas component.
`Cpa`, `Cpb`, `Cpc`, `Cpd`, `Cpe`	Molar heat capacity coefficients of the inflow gas at constant pressure. 4
`IAIR`	Flag to indicate that the following four fields define properties of the initial gas inside the structure.
`PAIR`	Initial pressure inside structure. Default=PATM (Real ≥ 0.0)
`TAIR`	Initial temperature inside structure. Default=TATM (Real ≥ 0.0)
`XMAIR`	Molar mass of air initially inside structure. No default (Real ≥ 0.0)
`Cpa_air`, `Cpb_air`, `Cpc_air`, `Cpd_air`, `Cpe_air`	Molar heat capacity coefficients of the initial air at constant pressure. 4 No default (Real ≥ 0.0)
`HYDRA`	Flag to indicate that the following fields define properties of incompressible/compressible fluid (implicit large displacement analysis only. Otherwise, the definition is ignored in analysis). 5, 6
`BULK`	Bulk modulus of compressible fluid inside structure If this is BLANK, the fluid inside the structure is incompressible. Default = BLANK (Real ≥ 0.0)

Comments

The volume must be a completely enclosed volume and the norm must be oriented outwards. If the structure contains a vent hole, the vent hole must be meshed with a shell element.
The value of the total vent hole coefficient must be between 0.0 and 1.0:

Total vent hole coefficient = min(max(C23 × LCTC23 × LCPC23, 0.0), 1.0).
There is no limit on the number of gas components.
Heat capacity at constant pressure:
$C p = C p a + C p b T + C p c T^{2} + C p d T^{3} + \frac{C p e}{T}$
Where, $T$ is temperature.
MONVOL with HYDRA continuation line can be used in an implicit large displacement analysis to model a cavity filled with ideal gas/hydraulic fluid. An element set must be used to define a cavity filled with the fluid. In this case, a result item called “fluid cavity (s)” with 4 sub results namely volume, cavity pressure, applied pressure and energy is available in HyperView. These results are available in the regular or the on-the-fly .h3d file. MONVOL for implicit large displacement analysis is supported for first and second order solid, shell, plane strain (CQPSTN, CTPSTN) and axisymmetric (CQAXI, CTAXI, CTRIAX6) elements.
In implicit large displacement analysis, Boyle’s law is used in ideal gas, which is:
P*V = P₀*V₀
In a compressible fluid case, the constitutive relation of the fluid is written as:
p = B*(V-V₀)/V₀
Where,

B

Bulk modulus

V

Current volume of the cavity

V₀

Initial volume of the cavity

p

Applied pressure
Support information for MONVOL:

Supported Analysis Types

Explicit Dynamic Analysis

Implicit Large Displacement Analysis