The Fluid Properties node adds the momentum and continuity equations solved by the physics interface, except for volume forces, which are added by the
Volume Force feature. The node also provides an interface for defining the material properties of the fluid.
By default, the Temperature model input is set to
Common model input, and the temperature is controlled from
Default Model Inputs under
Global Definitions or by a locally defined
Model Input. If a Heat Transfer interface is included in the component, it controls the temperature
Common model input. Alternatively, the temperature field can be selected from another physics interface. All physics interfaces have their own tags (
Name). For example, if a Heat Transfer in Fluids interface is included in the component, the
Temperature (ht) option is available for
T.
You can also select User defined from the
Temperature model input in order to manually prescribe
T.
The default Absolute pressure pA is
p+pref, where
p is the dependent pressure variable from the Navier-Stokes or RANS equations, and
pref is from the user input defined at the physics interface level. When
pref is nonzero, the physics interface solves for a gauge pressure. If the pressure field instead is an absolute pressure field,
pref should be set to 0.
The Absolute pressure field can be edited by clicking
Make All Model Inputs Editable (
) and entering the desired value in the input field.
The density can either be specified by a material, or by a User defined expression. The density in a material can depend on temperature and/or pressure and these dependencies are automatically replaced by
pref for weakly compressible flows and
pref and
Tref for incompressible flows (as specified by the
Compressibility setting at the physics interface level). If density variations with respect to pressure are to be included in the computations,
Compressibility must be set to compressible. Any dependencies in the density on quantities other than temperature and pressure must be consistent with the
Compressibility setting at the interface level.
The Dynamic viscosity μ describes the relationship between the shear rate and the shear stresses in a fluid. Intuitively, water and air have low viscosities, and substances often described as thick (such as oil) have higher viscosities.