Purpose

Assign a material to each simulation domain and review its flow and thermal properties. For fluid domains, choose the viscosity model in Domain properties.

Steps

1. In the Setup tab, click a domain or its material under Domains to open Domain properties.

   

2. Use Domain to select the domain to edit. Check its Fluid or Solid role as appropriate to the simulation.
3. Choose a library material in Material. To create a custom material, choose New →, enter a name in the adjacent field, and fill in the required properties.
4. For a fluid, choose Viscosity model. Newtonian uses a constant kinematic viscosity. Power law uses a viscosity that varies with shear rate and requires the minimum and maximum dynamic viscosity, consistency index m, and flow index n.
5. Review the enabled Flow and Thermal fields in the displayed units, then click Apply. Repeat for other domains as needed.

The image shows Air in a fluid domain with Turbulent flow, incompressible Flow type, and Heat model Off. Newtonian is selected; Power law is disabled because the flow is turbulent. Density and Viscosity are active, while Cp, k, and M are inactive for this configuration.

Inputs and units

Input or value	Meaning	Units
Domain / Fluid / Solid	Selects the domain and identifies its role in the simulation.	No physical units
Material	Library material, or New → for a named custom material.	No physical units
Viscosity model	Newtonian for constant viscosity, or Power law for shear-dependent viscosity.	No physical units
Density	Material reference density.	kg/m³; lb/ft³
Viscosity (Newtonian)	Constant kinematic viscosity for fluids.	m²/s; ft²/s
Minimum / Maximum viscosity (Power law)	Lower and upper bounds on the apparent dynamic viscosity.	Pa·s; psi·s
Consistency index m (Power law)	Coefficient in apparent viscosity = m × shear raten − 1, bounded by the minimum and maximum viscosity.	Pa·sⁿ; psi·sⁿ
Flow index n (Power law)	Below 1: shear thinning; 1: constant viscosity; above 1: shear thickening.	Dimensionless
Cp	Specific heat capacity; enabled for heat transfer or compressible fluid flow.	J/(kg·K); BTU/(lb·°F)
k	Thermal conductivity; enabled for heat transfer or compressible fluid flow.	W/(m·K); BTU/(h·ft·°F)
M	Molecular weight where required for a compressible gas.	kg/kmol; lbm/lbmol
Volumetric heat source	Signed source term available for a solid domain with heat transfer enabled.	W/m³, as labelled in the dialog

Limitations

• Power law requires Pro and supports single-fluid, incompressible, isothermal, laminar flow, steady or transient. Select Laminar in Flow mode to make Power law available with Pro. Compressible, mixture, thermal/CHT, and turbulent calculations are not supported with this model.
• Power-law material presets are disabled while Newtonian is selected. Choose a compatible material and viscosity model before applying.
• Required properties must be finite and positive. For Power law, the minimum viscosity must not exceed the maximum. Compressible-gas properties must also satisfy the material validation checks; constant properties may not represent a large temperature range.
• Solid domains are supported in CHT, which requires Pro. The volumetric heat source is shown only for a solid domain with heat transfer enabled and may be positive, negative, or zero.

Related topics

• Simulation type
• Units
• Heat
• Flow type
• Boundaries