10.1 Surface fluid cavities and fluid exchanges in Abaqus/CAE

Product: Abaqus/CAE

Benefits: You can now define surface fluid cavity and fluid exchange interactions and their associated interaction properties in Abaqus/CAE.

Description: Surface fluid cavities are used to model fluid-filled cavities such as tires and air springs for analysis. You create a fluid cavity interaction by selecting a reference node (cavity point) and the surface that defines the outer boundary of the cavity. You must assign a fluid cavity interaction property to complete the definition. You can create either a hydraulic or pneumatic interaction property for the cavity. Figure 10–1 shows the hydraulic and pneumatic entries for a fluid cavity interaction property.

Figure 10–1 Creating fluid cavity interaction properties.

The data for a hydraulic fluid cavity interaction property must include the fluid density. Optional parameters include:

Fluid bulk modulus (required for Abaqus/Explicit)
Fluid expansion coefficients
Temperature-dependent data for the fluid bulk modulus or the expansion coefficients
Field variables for the fluid bulk modulus or the expansion coefficients

The data for a pneumatic fluid cavity interaction property must include the ideal gas molecular weight. For an Abaqus/Explicit analysis you can also specify molar heat capacity in the interaction property using either a five-term polynomial form or a data table.

Fluid exchange interactions involve the movement of fluid between a cavity and the environment or between two cavities. To define a fluid exchange interaction, you select an existing cavity—or two in the case of exchange between cavities—and then select the interaction property that drives the fluid exchange. You must also include an effective exchange area; this represents the area through which the fluid flows during the exchange. Figure 10–2 shows the Edit Interaction dialog box for a fluid exchange between a cavity and the environment.

Figure 10–2 Editing a fluid exchange interaction.

The fluid exchange interaction property can be defined with one of the following methods:

Bulk viscosity
Mass flux
Mass rate leakage
Volume flux
Volume rate leakage

Fluid cavity and fluid exchange interactions must be defined in the initial step of an analysis. They are active for all steps, and you cannot change them in subsequent analysis steps.

Abaqus/CAE Usage:

Interaction module:
    Create Interaction; Step: Initial; Types for Selected Step: Fluid cavity: Select a cavity point and cavity
    surface; Select a fluid cavity interaction property

    Create Interaction; Step: Initial; Types for Selected Step: Fluid exchange: Select a definition:
    To environment or Between cavities; Select a fluid exchange interaction property

    Create Interaction Property; Type: Fluid cavity: Definition: Hydraulic or Pneumatic; 
    Enter the data to complete the selected definition

    Create Interaction Property; Type: Fluid exchange: Definition: Bulk viscosity, Mass flux, 
    Mass rate leakage, Volume flux, Volume rate leakage: Enter the data to complete the selected definition

References:

Abaqus Analysis User's Manual

Abaqus/CAE User's Manual