The Magnetohydrodynamics Interface
The Magnetohydrodynamics interface () is used to model the interaction between moving conducting fluids and magnetic fields. This multiphysics interface adds the Magnetic and Electric Fields and the Laminar Flow interfaces. The interface can be used to model a variety of magnetohydrodynamics phenomena in astrophysics, geophysics, metallurgy, and electrolytes. To model equilibrium discharges, use the dedicated Equilibrium Discharges interfaces in the Plasma Module.
Stationary and transient modeling are supported in 2D, 2D axisymmetric, and 3D. Also supported are combinations of frequency-domain modeling for the Magnetic Fields interface and stationary/transient modeling for the Laminar Flow interface, called frequency-stationary and frequency-transient modeling.
When a predefined Magnetohydrodynamics interface is added from the AC/DC>Electromagnetics and Fluids branch () of the Model Wizard or Add Physics windows, Magnetic and Electric Fields and Laminar Flow interfaces are added to the Model Builder. In addition, The Multiphysics Branch is added, which automatically includes the multiphysics coupling feature Magnetohydrodynamics.
On the Constituent Physics Interfaces
The Magnetic and Electric Fields interface computes electric field, current, and magnetic field distributions in conducting fluids. By default, it solves Ampère’s Law and current conservation equations in the computation domain.
The Laminar Flow interface solves for conservation of energy, mass, and momentum in fluids.
Settings for Physics Interfaces and Coupling Feature
When physics interfaces are added using the predefined couplings, for example Magnetohydrodynamics, specific settings are included with the physics interfaces and the coupling features.
In contrast, if physics interfaces are added one at a time, followed by the coupling features, these modified settings are not automatically included.
For example, if separate Electromagnetics and Fluids and Laminar Flow interfaces are added, COMSOL Multiphysics adds an empty Multiphysics node. When you right-click this node, you can choose Magnetohydrodynamics from a list of available coupling features but the modified settings are not included.
Table 7-4: Modified settings for a Joule heating interface.
Physics Interface or Coupling Feature
Modified Settings (if any)
Magnetic and Electric Fields
The discretization of the dependent variables is set to linear in 3D.
Laminar Flow
No changes.
Magnetohydrodynamics
The Domain Selection is the same as that of the participating physics interfaces
The corresponding Magnetic and Electric Fields and Laminar Flow interfaces are preselected in the Coupled Interfaces section.
Physics Interface and Coupling Feature
Coupling Feature
The Magnetohydrodynamics multiphysics coupling node is described in the next section.
Physics Interface Features
Physics nodes are available from the Physics ribbon toolbar (on Windows), the Physics context menu (on macOS and Linux), or by right-clicking to access the context menu (all platforms).