The Arc Discharge Multiphysics Interface
The Arc Discharges () multiphysics interface is used to study electric arc discharges (fully ionized) in a magnetohydrodynamics (MHD) framework. This multiphysics interface adds three single physics interfaces: Magnetic and Electric Fields, Heat Transfer in Fluids, and Laminar Flow, together with several multiphysics coupling features. The multiphysics couplings add the MHD coupling between the Magnetic and Electric Fields and the Laminar Flow interfaces. The multiphysics couplings also add heating and cooling of the equilibrium plasma by enthalpy transport, Joule heating and radiation loss.
When a predefined Arc Discharges interface is added from the Electric Discharge branch () of the Model Wizard or Add Physics windows, Magnetic and Electric Fields, Heat Transfer in Fluids, and Laminar Flow interfaces are added to the Model Builder. In addition, the Multiphysics Couplings node is added, which automatically includes the multiphysics coupling features Equilibrium Discharge Heat Source and Magnetohydrodynamics.
On the Constituent Physics Interfaces
The Electric Discharge Module includes the essential features of its constituent physics interfaces. However, access to some advanced features and functionalities requires additional licenses, such as the AC/DC Module license or the CFD Module license.
The Magnetic and Electric Fields interface is used to compute magnetic field and induced current distributions in and around coils, conductors, and magnets. The Magnetic and Electric Fields interface solves Maxwell’s equations formulated using the magnetic vector potential and, optionally for coils, the scalar electric potential as the dependent variables.
The Heat Transfer in Fluids interface provides features for modeling heat transfer by conduction, convection, and radiation. A Fluid model is active by default on all domains. All functionality for including other domain types, such as a solid domain, is also available. The temperature equation defined in solid domains corresponds to the differential form of the Fourier’s law that may contain additional contributions like heat sources.
The Laminar Flow interface solves for conservation of energy, mass, and momentum in fluids.
For details about predefined multiphysics couplings, see Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Settings for Physics Interfaces and Coupling Features
When physics interfaces are added using the predefined couplings, for example Arc Discharges, specific settings are included with the physics interfaces and the coupling features.
However, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.
For example, if single Magnetic and Electric Fields, Heat Transfer in Fluids, and Laminar Flow interfaces are added, COMSOL Multiphysics adds an empty Multiphysics Couplings node. You can then choose from the available coupling features, Equilibrium Discharge Heat Source, Magnetohydrodynamics, Nonisothermal Flow, and Equilibrium Discharge Boundary Heat Source but the modified settings are not included.
Coupling features are available from the context menu (right-click the Multiphysics Couplings node) or from the Physics toolbar’s Multiphysics menu.
Table 3-1: Modified Settings for an Arc Discharge Interface.
Physics Interface or Coupling Feature
Modified Settings
Magnetic and Electric Fields
The discretization of the dependent variables is set to linear. The Ampère's Law and Current Conservation in Fluids feature is added.
Heat Transfer in Fluids
In the Fluid default feature, the Absolute pressure, pA (Model Input section) and the Velocity field, u (Heat Convection section) are set to Common model input.
Laminar Flow
The Compressibility option is set to Compressible flow (Ma<0.3).
Equilibrium Discharge Heat Source
The Domain Selection is the same as that of the participating physics interfaces. The corresponding Magnetic Fields and Heat Transfer in Fluids interfaces are preselected in the Coupled Interfaces section.
Magnetohydrodynamics
The Domain Selection is the same as that of the participating physics interfaces. The corresponding Magnetic Fields and Laminar Flow interfaces are preselected in the Coupled Interfaces section.
Physics Interface and Coupling Features
Use the online help in COMSOL Multiphysics to locate and search all the documentation. All these links also work directly in COMSOL Multiphysics when using the Help system.
Coupling Features
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The Equilibrium Discharge Heat Source and Equilibrium Discharge Boundary Heat Source multiphysics coupling nodes are described in this chapter.
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The Magnetohydrodynamics multiphysics coupling node is described in this chapter.
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The Nonisothermal Flow coupling node is described for The Nonisothermal Flow and Conjugate Heat Transfer Interfaces in the COMSOL Multiphysics Reference Manual.
Physics Interface Features
Physics nodes are available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or right-click to access the context menu (all users).
In general, to add a node, go to the Physics toolbar, no matter what operating system you are using.
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The available physics features for The Laminar Flow Interface are listed in the section Domain, Boundary, Pair, and Point Nodes for Single-Phase Flow.
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The available physics features for the heat transfer interfaces are listed in the sections Domain Features, Boundary Features, and Edge and Point Features in the COMSOL Multiphysics Reference Manual.
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The available physics features for The Magnetic and Electric Fields Interface are listed in the section Domain, Boundary, Edge, Point, and Pair Nodes for the Magnetic and Electric Fields Interface.