The fluid link properties determine the mass flow rate through the link. The mass flow rate is specified as a function of the pressure differential and may also depend on the average pressure and temperature as well as external field variables. The fluid link will account for differences in fluid density between the cavities. The density in each cavity is a function of the temperature and, for compressible materials, of the pressure in the cavity. The conversion of the mass flow rate into volume flow rates at the ends is based on the fluid properties given for the cavity or cavities. Hence, the volume flow rates at the ends of the link may not balance.
Two methods are available for specifying the mass flow rate. In either case you must associate the mass flow rate with a set of fluid link elements.
Specifying a functional relationship between the mass flow rate and pressure difference
You can define an implicit functional relationship between the mass flow rate, q, and the pressure difference, , between the two nodes:
and the subscripts 1 and 2 refer to nodes 1 and 2 of the element. This method is the default for specifying the mass flow rate. The viscous resistance coefficient,
, and the hydrodynamic resistance coefficient,
, can be functions of the average pressure,
, and average temperature,
, in the link, as well as the average of any user-defined field variables in the link. A positive value of q
corresponds to flow from the first cavity to the second.
Specifying a table of mass flow rate versus pressure difference
You can input a table of q versus , , , and field variables. ABAQUS will interpolate linearly between values specified in the table. If one of the independent variables is outside the range of specified values, ABAQUS will use the value that is closest in the table.