The Reacting Flow, Diluted Species Coupling Feature
The Reacting Flow, Diluted Species () multiphysics coupling is used to simulate mass transport and reactions in a gas or liquid.
Domain Level Synchronization
The Reacting Flow, Diluted Species coupling synchronizes the features from a Single-Phase Flow, or Brinkman Equations, interface and a Transport of Diluted Species interface. When added, the velocity field used by the Transport of Diluted Species interface is synchronized to the one computed in the fluid flow interface.
Turbulent Mass Transfer
When a turbulence model is used, the Reacting Flow, Diluted Species coupling applies turbulence modeling for the mass transport in the following manners:
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Turbulent mass transport is added, defined from the turbulent viscosity and a turbulent Schmidt number (for more information, see Turbulent Mass Transport Models).
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Mass transport wall functions. When a turbulence model using wall functions is used for the fluid flow, the Reacting Flow coupling automatically adds wall functions for the mass transport on the same boundaries (for more information, see Mass Transport Wall Functions).
Settings
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 rfd1.
Domain Selection
The Reacting Flow, Diluted Species coupling is automatically defined on the intersection of the selections for the coupled interfaces.
The Selection list displays the domains where the coupling feature is active.
Coupled Interfaces
This section defines the physics involved in the multiphysics coupling. The Fluid flow and Species transport lists include all applicable physics interfaces.
The default values depend on how this coupling node is created.
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If it is added from the Physics ribbon (Windows users), Physics contextual toolbar (macOS and Linux users), or context menu (all users), then the first physics interface of each type in the component is selected as the default.
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If it is added automatically when a multiphysics interface is chosen in the Model Wizard or Add Physics window, then the two participating physics interfaces are selected.
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 Fluid Flow list defaults to None as there is nothing to couple to.
Click the Go to Source buttons () to move to the main physics interface node for the selected physics interface.
If a physics interface is deleted and then added to the model again, then in order to reestablish the coupling, you need to choose the physics interface again from the Fluid flow or Species transport lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Turbulence
When the fluid 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).
The turbulent mass transfer added to the concentration equations is defined as
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.