Marangoni Effect
The Marangoni Effect multiphysics coupling () accounts for Marangoni convection. Marangoni convection occurs when the surface tension of an interface (generally liquid-air) depends on the concentration of a species or on the temperature distribution. In the case of temperature dependence, the Marangoni effect is also called thermo-capillary convection. It is of primary importance in the fields of welding, crystal growth, and electron beam melting of metals.
The Marangoni effect is a shear stress which depends on the tangential temperature gradient and should be implemented as such. It has the following contribution described by forces induced on the fluid/fluid interface:
where γ is the temperature derivative of the surface tension σ (N/(m·K)). Note that this formulation is intended for laminar flow regimes only.
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 me1.
Surface Tension
Select a Surface tension coefficient type: Library coefficient, liquid/gas interface, or User defined (the default).
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For Library coefficient, liquid/gas interface choose an option from the Library surface tension coefficient list.
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For User defined enter a Surface tension coefficient σ (SI unit: N/m).
Marangoni Effect
This section defines the physics involved in the multiphysics coupling. The Fluid flow and Heat transfer 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 (Mac 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, Heat Transfer in Fluids is deleted — then the Heat transfer list defaults to None as there is nothing to couple to.
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 Heat transfer lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present interface. See Multiphysics Modeling Approaches in the COMSOL Multiphysics Reference Manual.
Marangoni Effect: Application Library path Heat_Transfer_Module/Tutorials,_Forced_and_Natural_Convection/marangoni_effect
Location in User Interface
Context menus
 Multiphysics>Marangoni Effect
when any of the following interface is added together with Heat Transfer in Solids (or another version of the Heat Transfer Interface):
Single-Phase Flow (any version)
Porous Media and Subsurface Flow, Brinkman Equations