Flow Coupling

The multiphysics coupling (

) defines u and p variables in order to set the model inputs in the Heat Transfer interface (or when applicable, a chemical species transport interface). In addition it provides all the fluids quantities that may be needed by the Heat Transfer interface (for example, viscosity, turbulence parameters, and so on).

Settings

The is the default multiphysics coupling feature name.

The 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 field. The first character must be a letter.

The default (for the first multiphysics coupling feature in the model) is fc1.

Coupled Interfaces

This section defines the physics involved in the multiphysics coupling. By default, the applicable physics interface is selected in the list to apply the to its physics interface to establish the coupling.

You can also select from either list to uncouple the node from a physics interface. If the physics interface is removed from the , for example is deleted, then the list defaults to as there is nothing to couple to.


	When the Destination interface is a heat transfer interface, the Nonisothermal Flow coupling node should be preferred to Flow Coupling. Indeed, Nonisothermal Flow brings an optimized stabilization; supports natural convection, including Boussinesq approximation; supports turbulent flow (wall functions, effective thermal conductivity); and handles work due to the pressure forces and viscous dissipation.


	When the Destination interface is a chemical species transport interface, a Reacting Flow coupling node should be used instead of Flow Coupling. See The Reacting Flow Multiphysics Interfaces for more details.


	If a physics interface is deleted and then added to the model again, and in order to re-establish the coupling, you need to choose the physics interface again from the lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present physics interface. See Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.