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Material Property

Material properties are volume conditions in the Multiphase module pertaining to selected Volumes.

The properties and conditions for the components and mixtures are specified in different modules-Flow, Heat and Common. The properties under the Multiphase module are interlinked with the properties under the same name in other modules.

  

Figure 5.100 - Material properties
Density

The method for computingDensity of the mixture can be specified under both the Multiphase and Common modules as follows:

or

Density of a mixture is computed from the densities of the individual components using either of the two methods:

  • Vol. Fraction Average: This computes the fluid density for the mixture in a selected volume by averaging the density of the components, based on their respective volume fractions.
  • User Specified: This directly sets the average fluid density for the mixture in a selected volume based on a user-defined function or fixed Value regardless of the density of the individual components.
  

Figure 5.101 - Density options

Density of components is specified only under the Common module as any of the following: Constant Density, Ideal Gas Law, Isentropic Gas Law, Compressible Liquid or User Specified using the Expression Editor.

Specify the Density of the components as shown below:

 

Viscosity

The Viscosity for the mixture can be specified under both the Multiphase and Flow module as follows:

or

Viscosity of a mixture is computed from the viscosities of the individual components using either of the three methods:

  • Vol. Fraction Average: This computes the viscosity of the mixture in a selected volume by averaging the viscosity of the components, based on their respective volume fractions.
  • Mass Fraction Average: This computes the viscosity of the mixture in a selected volume by averaging the viscosity of the components, based on their respective mass fractions.
  • User Specified: This directly sets the viscosity of the mixture in a selected volume based on a user-defined function or fixed Value regardless of the viscosity of the individual components.
  

Figure 5.102 - Viscosity options

 

Viscosity of components is specified only under the Flow module as any of the following: Constant Dynamic Viscosity, Constant Kinematic Viscosity, Sutherland Law, Bingham Models, Herschel-Bulkley Model, User Defined Function (Non Newtonian) or User Specified using the Expression Editor.

Specify the Viscosity of the components as shown below:

 

For Multiphase flow problems involving heat transfer, the following conditions, Enthalpy Model and Conductivity are specified.

Enthalpy Model

The Enthalpy Model for the mixture can be specified under both the Multiphase and Heat module as follows:

or

Enthalpy Model of a mixture is computed from the enthalpies of the individual components using either of the two methods:

  • Mass Fraction Average: This computes the fluid enthalpy of the mixture in a selected volume by averaging the enthalpy of the components, based on their respective mass fractions.
  • User Specified: This directly sets the enthalpy of the mixture in a selected volume based on a user-defined function or fixed Value regardless of the enthalpy of the individual components.
  

Figure 5.103 - Enthalpy model

 

The Enthalpy Model of the components are specified only under the Heat module as any of the following: Constant Capacity, JANAF Table, User Defined Function (Non Newtonian) or User Specified using the Expression Editor.

Specify the Enthalpy Model of the components as shown below:

 

Conductivity

Conductivity of a mixture can be specified under both the Multiphase and Heat module as follows:

or

Conductivity of a mixture is computed from the conductivities of the individual components using either of the two methods:

  • Vol. Fraction Average: This computes the conductivity of the mixture in a selected volume by averaging the conductivity of the components, based on their respective volume fractions.

  • User Specified: This directly sets the conductivity of the mixture in a selected volume based on a user-defined function or fixed Value regardless of the conductivity of the individual components.
  

Figure 5.104 - Conductivity options

 

Conductivity of the components is specified only under the Heat module using any of the following: Constant Prandtl Number, Constant Conductivity or User Specified using the Expression Editor.

Specify the Conductivity of the components as shown below:

 

Surface Tension

This allows considering the surface tension for components in a selected volume. The Surface Tension can only be activated under the Flow module for the components making up the mixture. Specify the Surface Tension for the components in the selected volumes as given below:

  • Geometric Entities Panel > Volumes > [Desired Volume]
  • Properties Panel > Model Tab > Flow > Component {Name of the Component} > Surface Tension > [ No or Surface Tension]

 

Surface Tension and the associated Value should only be selected for one of the components. (The others should be set to Surface Tension > No). Whether surface tension needs to be activated depends on its magnitude relative to momentum and other forces. Weber number and Bond number serve as a measure whether to activate surface tension.

  

Figure 5.105 - Surface tension
 

Note: Surface tension depends on the combined properties of the fluids on either side of the interface. But for the current release, surface tension is limited to associating it to only one component, even for multiple fluids.

 

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