8.1 Defining Materials

An important step in the setup of the model is to define the materials and their physical properties. Material properties are defined in the Materials task page, where you can enter values for the properties that are relevant to the problem scope you have defined in the Models task page. These properties may include the following:

• density and/or molecular weights

• viscosity

• heat capacity

• thermal conductivity

• UDS diffusion coefficients

• mass diffusion coefficients

• standard state enthalpies

• kinetic theory parameters

Properties may be temperature-dependent and/or composition-dependent, with temperature dependence based on a polynomial, piecewise-linear, or piecewise-polynomial function and individual component properties either defined by you or computed via kinetic theory.

The Materials task page will show the properties that need to be defined for the active physical models. If any property you define requires the energy equation to be solved (e.g., ideal gas law for density, temperature-dependent profile for viscosity), ANSYS FLUENT will automatically activate the energy equation. Then you have to define the thermal boundary conditions and other parameters yourself.

Physical Properties for Solid Materials

For solid materials, only density, thermal conductivity, and heat capacity are defined. If you are modeling semi-transparent media, case radiation properties are also defined. You can specify a constant value, a temperature-dependent function, or a user-defined function for thermal conductivity; a constant value or temperature-dependent function for heat capacity; and a constant value for density.

If you are using the pressure-based solver, density and heat capacity for a solid material are not required unless you are modeling transient flow or moving solid zones. Heat capacity will appear in the list of solid properties for steady flows as well. The value will be used just for postprocessing enthalpy; not in the calculation.