Use the Reacting Flow () multiphysics coupling to simulate mass transport and reactions in a gas or liquid mixture where the fluid flow can be dependent on the mixture composition.

The Reacting Flow coupling synchronizes the features from a Single-Phase Flow, or Brinkman Equations, interface and a Transport of Concentrated Species interface. When added, the density in the Single-Phase Flow interface is automatically synchronized to the one defined by the Transport of Concentrated Species interface. Conversely, the velocity field used by the latter interface is synchronized to the one computed in the former interface.

The Reacting Flow coupling feature automatically couples mass transfer on boundaries and applies a corresponding velocity contribution for the flow. Prescribing a net mass boundary flux in the Transport of Concentrated Species interface, either using a Flux or Mass Fraction feature, the Reacting Flow feature computes the The Stefan Velocity, and applies this in Wall features using the same selection.

When coupled to the Brinkman Equations interface, the Reacting Flow node automatically computes the net mass source or sink in a Reactions (when Mass transfer to other phases is enabled) node in the Transport of Concentrated Species interface and adds the corresponding source/sink to the momentum equations of the Fluid and Matrix Properties domains.

When a turbulence model is used, the Reacting Flow coupling applies turbulence modeling for the mass transport in the following manners:

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 rf1.

When the flow interface uses a turbulence model, select an option from the Mass transport turbulence model list—Kays-Crawford, High Schmidt Number, or User-defined turbulent Schmidt number.

For User-defined turbulent Schmidt number, enter a Turbulent Schmidt number ScT (dimensionless).

where μT is the turbulent viscosity defined by the flow interface, and the turbulent Schmidt number, ScT, depends on the Mass transport turbulence model used.

Note, since the Reacting Flow coupling feature adds the turbulent mass transport, it should not be combined with a Turbulent Mixing feature (subfeature to Transport Properties in the Transport of Concentrated Species interface).

This section defines the physics involved in the multiphysics coupling. The Fluid flow and Species transport 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 Laminar Flow is deleted, then the Species transport list defaults to None as there is nothing to couple to.