The Laser Heating Interface
The Laser Heating interface () is used to model electromagnetic heating for systems and devices where the electric field amplitude varies slowly on a wavelength scale. This multiphysics interface adds an Electromagnetic Waves, Beam Envelopes interface and a Heat Transfer in Solids interface. The multiphysics couplings add the electromagnetic losses from the electromagnetic waves as a heat source, and the electromagnetic material properties can depend on the temperature. The modeling approach is based on the assumption that the electromagnetic cycle time is short compared to the thermal time scale.
Combinations of frequency-domain modeling for the Electromagnetic Waves, Beam Envelopes interface and stationary modeling for the Heat Transfer in Solids interface, called frequency-stationary and, similarly, frequency-transient modeling, are supported in 2D and 3D. For these study types, the coupling between the frequency-domain modeling of the electromagnetic part and the stationary or transient modeling of the heat transfer part is bidirectional: the electromagnetic part defines a heat source for the heat transfer problem and the temperature distribution from the heat transfer problem can influence the material properties in the electromagnetic problem.
If the coupling is unidirectional — that is, if the electromagnetic problem does not depend on the temperature — Frequency-Stationary, One-Way Electromagnetic Heating and Frequency-Transient, One-Way Electromagnetic Heating studies can be added from the Model Wizard. These studies give, respectively, a Frequency Domain study step for the electromagnetic problem followed by a Stationary or Time Dependent study step for the heat transfer problem.
When a predefined Laser Heating interface is added from the Heat Transfer>Electromagnetic Heating branch () of the Model Wizard or Add Physics window, Electromagnetic Waves, Beam Envelopes and Heat Transfer in Solids interfaces are added to the Model Builder.
In addition, a Multiphysics node is added, which automatically includes the multiphysics coupling feature Electromagnetic Heat Source.
On the Constituent Physics Interfaces
The Electromagnetic Waves, Beam Envelopes interface computes electric and magnetic field distributions for systems and devices where the field amplitude varies slowly on a wavelength scale. The physics interface can be used efficiently for unidirectional and bidirectional propagation of electromagnetic beams. In this physics interface, the electric field is factored into a product of a slowly varying envelope function (slowly on the scale of a wavelength) and a rapidly varying phase function. The phase function is a priori prescribed, so the physics interface solves the time-harmonic wave equation for the slowly varying envelope function.
The Heat Transfer in Solids interface provides features for modeling heat transfer by conduction, convection, and radiation. A Heat Transfer in Solids model is active by default on all domains. All functionality for including other domain types, such as a fluid domain, is also available. The temperature equation defined in solid domains corresponds to the differential form of Fourier’s law that may contain additional contributions like heat sources.
Settings for Physics Interfaces and Coupling Feature
When physics interfaces are added using the predefined couplings, for example Laser Heating, 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 Electromagnetic Waves, Beam Envelopes and Heat Transfer in Solids interfaces are added, COMSOL Multiphysics adds an empty Multiphysics node. You can add the Electromagnetic Heating coupling feature, but no modified settings are included.
Coupling features are available from the context menu (right-click the Multiphysics node) or from the Physics toolbar, Multiphysics menu.
Table 4-1: Modified Settings for a Laser Heating Interface
Physics Interface or Coupling Feature
Modified Settings (if any)
Electromagnetic Waves, Beam Envelopes
No changes.
Heat Transfer in Solids
No changes.
Electromagnetic Heating
The Domain Selection is the same as that of the participating physics interfaces.
The Boundary Selection is the same as the exterior and interior boundaries of the Domain Selection of the participating physics interfaces.
The corresponding Electromagnetic Waves, Beam Envelopes and Heat Transfer in Solids interfaces are preselected in the Coupled Interfaces section (described in the COMSOL Multiphysics Reference Manual).
A side effect of adding physics interfaces one at a time is that four study types — Frequency-Stationary; Frequency-Transient; Frequency-Stationary, One-Way Electromagnetic Heating; and Frequency-Transient, One-Way Electromagnetic Heating — are not available for selection until after at least one coupling feature is added. In this case, it is better to initially not add any study at all, then add the coupling features to the Multiphysics node, and lastly, open the Add Study window and add a study sequence below the Preset Studies for Selected Multiphysics heading.
Physics Interfaces and Coupling Feature
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 Feature
The Electromagnetic Heating coupling feature node is described for The Joule Heating Interface 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. Subnodes are available by clicking the parent node and selecting it from the Attributes menu.
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The available physics features for The Electromagnetic Waves, Beam Envelopes Interface are listed in the section Domain, Boundary, Edge, and Point Nodes for the Electromagnetic Waves, Beam Envelopes Interface.
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The available physics features for The Heat Transfer Interfaces are listed in the section Feature Nodes for the Heat Transfer in Solids Interface in the COMSOL Multiphysics Reference Manual.