The Mixture Properties node contains the material properties for the continuous phase and the dispersed phase. It also contains settings for the viscosity model. For the Mixture Model, Turbulent Flow interfaces, the
Mixture Properties node also adds the equations for the turbulence transport equations.
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.
Select the fluid materials to use for the material properties. The default material used for the Continuous phase is the
Domain material. This corresponds to the material currently applied to the domain in question. The
Dispersed phase uses
None per default. A valid material must be selected instead.
The default Density, continuous phase ρc (SI unit: kg/m
3) uses values
From material (as selected in the
Materials section). For
User defined enter another value or expression. In this case the default is 0 kg/m
3.
The default Dynamic viscosity, continuous phase μc (SI unit: Pa·s), uses values
From material. It describes the relationship between the shear stresses and the shear rate in a fluid. Intuitively, water and air have a low viscosity, and substances often described as thick, such as oil, have a higher viscosity. For
User defined enter another value or expression. In this case, the default is 0 Pa·s.
The default Density, dispersed phase ρd (SI unit: kg/m
3) uses values
From material (as selected in the
Materials section). For
User defined enter another value or expression. In this case, the default is 0 kg/m
3.
Enter the Diameter of particles/droplets dd (SI unit: m). The default is 10
−3 m (1 mm). If
Haider-Levenspiel is selected for the
Slip model under
Physical Model, enter a value between 0 and 1 for the
Sphericity (dimensionless). The default is 1.
If Liquid droplets/bubbles is selected from the
Dispersed phase list in the interface, then
Dynamic viscosity, dispersed phase μd (SI unit: Pa·s) is also available. The default uses values
From material (as selected in the
Materials section) or select
User defined to enter another value or expression. In this case, the default is 0 Pa·s.
When a User defined Slip model is selected for the physics interface, specify an arbitrary expression for the relative velocity. For example, give a constant velocity based on experimental data.
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When Slip velocity is set to Specify slip velocity field, enter the slip velocity between the two phases, uslip (SI unit: m/s).
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When Slip velocity is set to Specify slip flux, enter the slip flux jslip (SI unit: m/s).
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Select the Mixture viscosity model.
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When Solid particles is the Dispersed phase, select either Krieger type (the default) or User defined.
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When Liquid droplets/bubbles is the Dispersed phase, select Krieger type (the default), User defined, or Volume averaged.
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For User defined enter a value or expression for the
Dynamic viscosity μ (SI unit: Pa
⋅s). The default is 0 Pa
⋅s. When using this option, make sure to limit the viscosity to bounded positive values.
When Krieger type is selected, enter a value or expression for the
Maximum packing concentration (dimensionless). The default is 0.62.
Select Volume averaged to model the mixture viscosity of liquid-liquid mixtures, which uses the following equation for the viscosity:
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. The default is 1 (that is, one unit length of the model unit system).
This section is available for The Mixture Model, Algebraic yPlus Interface, The Mixture Model, L-VEL Interface, The Mixture Model, SST Interface, The Mixture Model, Low Re k-ε Interface, The Mixture Model, Spalart–Allmaras Interface, and
The Mixture Model, v2-f Interface.
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.