Material Property
Material properties are volume conditions in the Multiphase module that refer to selected volumes.
The material properties appear in the Properties panel when you select a fluid domain in the Flow Analysis Tree under Domains.
Density
You can specify the density for a selected volume under the Multiphase and Common module in the Properties panel.
Density of a mixture is computed from the densities of the individual components by using the following options:
• Vol. Fraction Average—Calculates 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—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.
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 by using the Expression Editor.
Viscosity
The viscosity for the mixture is specified in Multiphase and Flow modules. Viscosity of a mixture is determined from the viscosities of the individual components using one of the following methods:
• Vol. Fraction Average—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—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—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.
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 (NonNewtonian) or User Specified using the Expression Editor.
For multiphase flow problems involving heat transfer, Enthalpy Model and Conductivity are specified.
Enthalpy Model
You can specify Enthalpy Model for the mixture under both the Multiphase and Heat modules.
Enthalpy model of a mixture is determined from the enthalpies of the individual components using one of the following methods:
• Mass Fraction Average—Fluid enthalpy of the mixture in a selected volume by averaging the enthalpy of the components, based on their respective mass fractions.
• User Specified—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.
The Enthalpy model of the components is specified only under the Heat module as one of the following: Constant Capacity, JANAF Table, User Defined Function (NonNewtonian) or User Specified using the Expression Editor.
Conductivity
You can specify conductivity of a mixture under both the Multiphase and Heat modules.
Conductivity of a mixture is computed from the conductivities of the individual components using one of the following methods:
• Vol. Fraction Average—Sets the conductivity of the mixture in a selected volume by averaging the conductivity of the components, based on their volume fractions.
• User Specified—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.
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.
Surface Tension
Consider the surface tension for components in a selected volume. The surface tension is only activated under the Flow module for the components that make up the mixture.
Surface tension and the associated value should only be selected for one component. Surface tension for the other components should be set to 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.
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Surface tension depends on the combined properties of the fluids on either side of the interface. For the current release, surface tension is limited to associating it to only one component, even for multiple fluids.
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