The Fluid Properties node contains the material properties for the liquid and the gas. It also contains settings for the slip model.
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 default Density, liquid phase ρl (SI unit: kg/m
3) uses values
From material. For
User defined enter another value or expression.
The default Dynamic viscosity, liquid phase μl (SI unit: Pa·s) uses values
From material;
the value is then defined for the material selected in the
Materials section for the continuous phase. For
User defined enter another value or expression.
The default Density, gas phase ρg (SI unit: kg/m
3) uses values
From material. For
User defined enter another value or expression. Alternatively, select
Calculate from ideal gas law and enter the
Molecular weight M (SI unit: kg/mol) of the gas.
Enter the Bubble diameter db (SI unit: m). The default value is 10
−3 m (1 mm).
Homogeneous flow assumes that the velocity of the two phases are equal; that is, uslip = 0. For
User defined enter different values or expressions for the components of the
Slip velocity uslip (SI unit: m/s).
For Pressure-drag balance it uses a model based on the assumption that the pressure forces on a bubble are balanced by the drag force:
Here db (SI unit: m) is the bubble diameter, and
Cd (dimensionless) is the drag coefficient.
This section is available for the Bubbly Flow, k-
ε, Bubbly Flow, Realizable
k-
ε, and Bubbly Flow,
k-
ω interfaces, where an upper limit on the mixing length is required.
When the Mixing length limit lmix, lim is set to
Automatic, the mixing length limit is evaluated as the shortest side of the geometry bounding box. If the geometry is, for example, a complicated system of slim entities, this measure can be too high. In such cases, it is recommended that the mixing length limit is defined manually. Select
Manual to enter a different value or expression.
This section is available for the Bubbly Flow, Low Re k-
ε, Bubbly Flow, Algebraic yPlus
, Bubbly Flow, L-VEL
, Bubbly Flow, SST
, Bubbly Flow, Spalart–Allmaras, and Bubbly Flow, v2-f interfaces.
When the Reference length scale lref is set to
Automatic, it is evaluated one tenth of the shortest side of the geometry bounding box. The solution to the wall distance equation is controlled by the parameter
lref. The distance to objects larger than
lref is represented accurately, while objects smaller than
lref are effectively diminished by appearing to be farther away than they actually are. This is a desirable feature in turbulence modeling because small objects would have too large an impact on the solution if the wall distance were measured exactly. The automatic value is usually a good choice but the value can become too high if the geometry consists of several slim entities. In such cases, it is recommended that the reference length scale is defined manually. Select
Manual to enter a different value or expression.