Fluid–Particle Interaction
The Fluid–Particle Interaction multiphysics coupling () computes a volume force that is equal in magnitude and opposite in direction to the total drag force exerted on particles in each mesh element in the selected domains. This volume force contributes to the total force acting on the fluid in the Laminar Flow interface.
Settings
The Label is the default multiphysics coupling 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 in the model) is fpi1.
Force Multiplication Factor
Use this section to specify a proportionality factor to multiply by the change in particle momentum when computing the volume force.
Select an option from the Force multiplication factor specification list: From physics (the default) or User defined.
If Specify mass flow rate is selected from the Particle Release and Propagation section in the Settings window for The Particle Tracing for Fluid Flow Interface, this section has no effect because the proportionality factor is based on the mass flow rate of particles, which is specified in the particle release features. Otherwise, the following conditions apply:
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If From physics is selected and the Enable macroparticles check box is cleared in the physics interface Additional Variables section, the multiplication factor is 1.
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If From physics is selected and the Enable macroparticles check box is selected in the physics interface Additional Variables section, the multiplication factor is based on the auxiliary dependent variable for the multiplication factor, which is typically specified in release feature settings. If the physics interface has name fpt, this variable has name fpt.nn.
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If User defined is selected, enter a value or expression for the Force multiplication factor n (dimensionless). The default is 1.
Coupled Interfaces
This section defines the physics involved in the multiphysics coupling. By default, the applicable physics interface is selected in the Source and Destination lists.
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 then the applicable list defaults to None as there is nothing to couple to.
If a physics interface is deleted and then added to the model again, and in order to reestablish the coupling, you need to choose the physics interface again from the Source or Destination lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present physics interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.