ABAQUS Keywords Reference Manual  

*FLUID CAVITY
Define a fluid cavity.

This option is used to define a surface-based fluid cavity.

Product: ABAQUS/Explicit  

Type: Model data

Level: Part  Part Instance  Assembly  

Reference:

Required parameters:

NAME

Set this parameter equal to the name to be used to identify the fluid cavity.

REF NODE

Set this parameter equal to either the node number of the fluid cavity reference node or the name of a node set containing the fluid cavity reference node. If the name of a node set is chosen, the node set must contain exactly one node.

Required, mutually exclusive parameters: 

BEHAVIOR

Set this parameter equal to the name of the *FLUID BEHAVIOR option defining the fluid behavior.

MIXTURE

Include this parameter if the fluid in the fluid cavity is a mixture of ideal gases.

Optional parameters:

ADDED VOLUME

Set this parameter equal to the magnitude of the additional volume for the fluid. The additional volume will be added to the actual volume of the cavity calculated by ABAQUS/Explicit.

ADIABATIC

This parameter is relevant only when an ideal gas model is used. Include this parameter if adiabatic behavior is assumed for the ideal gas.

AMBIENT PRESSURE

Set this parameter equal to the magnitude of the ambient pressure. For a pneumatic fluid, the ambient pressure will typically be atmospheric pressure.

MINIMUM VOLUME

Set this parameter equal to the magnitude of the minimum volume for the fluid. If the volume of the cavity (which is equal to the actual volume plus the added volume) drops below the minimum, the minimum value will be used to evaluate the equation of state model.

SURFACE

Set this parameter equal to the name of the surface forming the boundary of the fluid cavity. This parameter is required if the parameter ADDED VOLUME is omitted.

Data line if the BEHAVIOR parameter is included: 

First (and only) line:

  1. Out-of-plane thickness of the surface for two-dimensional models when the SURFACE parameter is included. If this value is left blank or is entered as zero, the default value of 1.0 will be used. Enter a blank line when the surface is defined by three-dimensional and axisymmetric elements or when the SURFACE parameter is omitted.

Data lines if the MIXTURE parameter is included: 

First line:

  1. Out-of-plane thickness of the surface for two-dimensional models when the SURFACE parameter is included. If this value is left blank or is entered as zero, the default value of 1.0 will be used. Enter a blank line when the surface is defined by three-dimensional and axisymmetric elements or when the SURFACE parameter is omitted.

Second line:

  1. Name of fluid behavior forming the gas mixture.

  2. Molecular mass fraction.

Repeat this data line as often as necessary to define the initial gas mixture.