Use the Nonisothermal Flow multiphysics coupling (
) to simulate fluid flows where the fluid properties depend on temperature. Models can also include heat transfer in solids. The physics interface supports low Mach numbers (typically less than 0.3).
This multiphysics coupling defines p and
u variables in order to set the
Absolute pressure in the
Model Input section and the
Velocity field in the
Heat Convection section of the
Fluid feature in the Heat Transfer interface. In addition, it provides all the fluids quantities that may be needed by the Heat Transfer interface (for example, viscosity).
The Label is the default multiphysics coupling feature name.
The Name is used primarily as a scope prefix for variables defined by the coupling node. Refer to such variables in expressions using the pattern
<name>.<variable_name>. In order to distinguish between variables belonging to different coupling nodes or physics interfaces, the
name string must be unique. Only letters, numbers, and underscores (_) are permitted in the
Name field. The first character must be a letter.
The default Name (for the first multiphysics coupling feature in the model) is
nitf1.
When nodes are added from the context menu, you can select Manual (the default) from the
Selection list to choose specific domains to define the nonisothermal flow, or select
All domains as needed.
This section defines the physics involved in the multiphysics coupling. The Fluid flow and
Heat transfer lists include all applicable physics interfaces.
You can also select None from either list to uncouple the node from a physics interface. If the physics interface is removed from the
Model Builder — for example,
Heat Transfer in Fluids is deleted — then the
Heat transfer list defaults to
None as there is nothing to couple to.
For Custom, linearized density, enter the
Reference density ρref (SI unit: kg/m
3) and the
Coefficient of thermal expansion αp(SI unit:1/K), or select
From material, or select a variable in the list if available. When
Custom, linearized density is selected, regardless how the properties are defined they should be constant. If material properties are not constant you should consider using any of the other options to define the density.
For Custom, enter a
Density ρ (SI unit: kg/m
3), or select a density in the list if available.
The density definition in the Nonisothermal Flow node ensures that the same definition of the density is used on the fluid flow and heat transfer interfaces. When the fluid flow compressibility setting is set to
Incompressible then the thermal conductivity and the heat capacity are evaluated at the
Reference temperature defined in the fluid flow interface.
when any version of the Single-Phase Flow interface is added together with
Heat Transfer in Fluids (or another version of the Heat Transfer Interface, with a
Fluid feature active).