For a steady-state problem the temperature does not change with time, and the first term disappears.

This section is available when material properties are temperature-dependent. By default, the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 K by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.

It is also used if the ideal gas law is applied. See Thermodynamics, Fluid.

The default Absolute pressure pA is taken from Common model input. It corresponds to the minput.pA variable, set to 1 atm by default. To edit it, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Pressure in the Expression for remaining selection section. When additional physics interfaces are added to the model, the absolute pressure variables defined by these physics interfaces can also be selected from the list. For example, if a Laminar Flow interface is added you can select Absolute pressure (spf) from the list. The last option is User defined.

This section is available only when the Local Thermal Nonequilibrium multiphysics coupling is included in the component to model porous media. It makes it possible to define different material properties for the fluid phase when the domain material corresponds to the solid phase (porous matrix) material.

Select any material from the list to define the Fluid material. The default uses the Domain material.

The default Velocity field u is User defined. For User defined enter values or expressions for the components based on space dimensions. Or select an existing velocity field in the component (for example, Velocity field (spf) from a Laminar Flow interface). The Common model input option corresponds to the minput.u variable. To edit it, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set values for the Velocity components in the Expression for remaining selection section.

The thermal conductivity k describes the relationship between the heat flux vector q and the temperature gradient ∇T in q = −k∇T, which is Fourier’s law of heat conduction. Enter this quantity as power per length and temperature.

The default Thermal conductivity k is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity, and enter values or expressions for the thermal conductivity or its components. For Isotropic enter a scalar which will be used to define a diagonal tensor. For the other options, enter values or expressions into the editable fields of the tensor.

The heat capacity at constant pressure Cp describes the amount of heat energy required to produce a unit temperature change in a unit mass.

The ratio of specific heats γ is the ratio between the heat capacity at constant pressure, Cp, and the heat capacity at constant volume, Cv. When using the ideal gas law to describe a fluid, specifying γ is sufficient to evaluate Cp. For common diatomic gases such as air, γ = 1.4 is the standard value. Most liquids have γ = 1.1 while water has γ = 1.0. γ is used in the streamline stabilization and in the variables for heat fluxes and total energy fluxes. It is also used if the ideal gas law is applied.

When the density is not taken from a Nonisothermal Flow or a Nonisothermal Mixture Model coupling node, you should select a Fluid type option for the specification of the material properties. The available Fluid type options are From material, Ideal gas, and Gas/Liquid (default). After selecting a Fluid type from the list, further settings display underneath. See Nonisothermal Mixture Model in the CFD Module User’s Guide for details.

This option automatically detects whether the material applied on each domain selection is an ideal gas or not, and uses the relevant properties from the Material node for either case.

with Rs the specific gas constant, pA the absolute pressure, and T the temperature, the evaluation of the isobaric compressibility coefficient, αp, and of the isothermal Joule-Thomson coefficient, μJT, is simplified. This may improve efficiency, when computing pressure work in compressible nonisothermal flows for example, or when modeling inflow conditions.

The Density, the Heat capacity at constant pressure, and the Ratio of specific heats are automatically taken From material and no further setting is required. For the specification of user defined material properties, the Ideal Gas or Gas/Liquid options should be used instead.

This option specifies the Density, the Heat capacity at constant pressure, and the Ratio of specific heats for a general gas or liquid.

Physics Tab with interface as Heat Transfer in Solids and Fluids, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media, Heat Transfer in Building Materials or Bioheat Transfer selected: