About Fluid Cavities

A fluid cavity models a fluid-filled structure to simulate its mechanical response. Fluid cavity applications include pressure vessels and hydraulic driving mechanisms. You can define fluid cavities that are filled with hydraulic, pneumatic, or user-defined fluids.

This page discusses:

See Also
Defining Fluid Cavities

Mechanical Behavior

A fluid cavity structure is typically subjected to an external load, while the fluid inside the structure exerts internal pressure. Both the external load and the internal pressure dictate the structure's response (that is, its deformation), which creates a feedback loop for the external load and internal pressure to deform the structure further. The app provides the analysis coupling required to simulate cases in which you assume the cavity is filled completely by a fluid with uniform properties and state—it calculates the deformation of the structure and the pressure exerted by the fluid on the boundary surface.

Fluid Cavity Material Properties

The material assigned to a fluid cavity defines the type of fluid occupying the cavity and its material properties. Hydraulic fluid materials must include fluid density, fluid bulk modulus, and fluid expansion; pneumatic fluid materials must include molecular weight and molar heat capacity; and user-defined fluid materials must include the user-defined fluid material option and user subroutine UFLUID.

The app does not consider other fluid-related material properties, such as equation of state and the ideal gas behavior, in the solution. You use these material properties only for analyses in the Fluid Model Creation or Fluid Scenario Creation apps. In general, you should review the material definition before selecting a fluid for a fluid cavity feature.