A D V A N C E D S E T T I N G S

To display this section, click the Show button () and select Advanced Physics Interface Options. Normally these settings do not need to be changed. From the

Regularization list, select On (default) or Off.

When turned On, regularized mass fractions are calculated such that 0 wi reg 1 . Regularized mass fractions are used to for the calculation of composition-dependent material properties, such as the density.

D I S C R E T I Z A T I O N

To display this section, click the Show button () and select Discretization. Select a

Frame type—Spatial (the default) or Material. Select Linear (the default), Quadratic, Cubic, or Quartic for the element order of the elements for the Mass fraction.

C O N S I S T E N T A N D I N C O N S I S T E N T S T A B I L I Z A T I O N

To display this section, click the Show button () and select Stabilization. Settings unique to this interface are listed below.

•There are two consistent stabilization methods that are available when using the Mixture-Averaged or Fick’s Law diffusion model—Streamline diffusion and

Crosswind diffusion. Both are active by default.

•There is one inconsistent stabilization method, Isotropic diffusion, which is available when using the Mixture-Averaged or Fick’s Law diffusion model.

•Model Builder Options for Physics Feature Node Settings Windows

•Theory for the Transport of Concentrated Species Interface

•Transport Feature

• Reactions

See Also

• Initial Values

• Boundary Conditions for the Transport of Concentrated Species Interface

Transport Feature

The Transport node adds the equations for transport of concentrated species and provides inputs for the material properties. The feature is dynamic and includes the input fields required by the active transport mechanisms and diffusion model. The name of the transport feature is composed of the included transport mechanisms, and

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can be one of the following—Diffusion, Diffusion and Migration, Convection and Diffusion, or Convection, Diffusion, and Migration.

D O M A I N S E L E C T I O N

From the Selection list, choose the domains to apply the transport feature.

M O D E L I N P U T S

Specify the velocity field, the pressure, and the temperature to be used in the interface. The velocity becomes the model input for the convective part of the transport. The temperature model input is used when calculating the density from the ideal gas law, but also when thermal diffusion is accounted for by supplying thermal diffusion coefficients. If the model includes migration, the model input section also includes the electric potential as the model input for transport due to migration.

Select the source of the Velocity field u:

-Select User defined to enter values or expressions for the velocity components (SI unit: m/s) in the field that appears. This input is always available.

-In addition, select velocity fields defined by a fluid-flow interface present in the model (if any). For example, then select Velocity field (spf/fp1) to use the velocity field defined by the Fluid Properties feature fp1 in a single-phase flow interface spf.

Select the source of the absolute Pressure pa:

-Select User defined to enter a value or an expression for the absolute pressure (SI unit: Pa) in the field that appears. This input is always available.

-In addition, select a pressure defined by a fluid-flow interface present in the model (if any). For example, then select Pressure (spf/fp1) to use the pressure defined by the Fluid Properties feature fp1 in a Single-Phase Flow interface spf.

Selecting a pressure variable also activates a check box for defining the reference pressure, where 1 [atm] has been automatically included. This allows the use of a system-based (gauge) pressure, while automatically including the reference pressure in the absolute pressure.

Select the source of the Temperature field T:

-Select User defined to enter a value or an expression for the temperature (SI unit: K). This input is always available.

-If required, select a temperature defined by a heat transfer interface present in the model (if any). For example, then select Temperature (ht/fht1) to use the

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temperature defined by the Fluid Heat Transfer feature fht1 in a Heat Transfer interface ht.

When the transport feature includes migration, select the source of the Electric potential V:

-Select User defined to enter a value or expression for the electric potential (SI unit: V). This input is always available.

-If required, select an electric potential defined by an electromagnetics interface that is present in the model (if any). For example, then select Electric potential (ec/ cucn1) to use the electric field defined by the Current Conservation node cucn1 in an Electric Currents interface ec.

D E N S I T Y

Define the density of the mixture and the molar masses of the participating species.

Mixture Density

Select a way to define the density from the Mixture density list:

• Select Ideal gas (the default) to use the ideal gas law

pM

= -----------

RgT

law to compute the mixture density using the absolute pressure and temperature defined in the Model inputs section.

•Select User defined to enter a value or expression for the mixture density in the density field that appears.

Molar Mass

Enter a value or expression for the Molar mass M (SI unit: kg/mol) of each species. The default value for each species is 0.032 kg/mol, which is the molar mass of O2 gas.

D I F F U S I O N

Specify the molecular and thermal diffusivities of the present species. Using a Mixture-averaged diffusion model, specify the Maxwell-Stefan diffusivity matrix Dik, and when using a Fick’s law diffusion model, specify the Diffusion coefficient DFi for each of the species.

Maxwell-Stefan Diffusivity Matrix

Using a Mixture-averaged diffusion model, the Maxwell-Stefan diffusivity matrix Dik (SI unit: m2/s) can be specified. For a simulation involving Q species the Maxwell-Stefan

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