New Functionality in Version 4.1

This release of the AC/DC Module includes a number of new capabilities. Some of the most important ones are the following:

  • The Electric Currents physics interface contains the possibility to model electric currents in saturated porous media for fluids and solids with different conductivities and permittivities.
  • Archie’s law for porous media
  • The formulation of the boundary conditions in the Magnetic and Electric fields interface has been updated to make them more user-friendly.

The following addition to the new functionality in COMSOL Multiphysics is of special interest for users of the AC/DC Module:

  • Frequency-domain transformation using FFT for computing frequency spectra from time-dependent simulations.

Backward Compatibility vs. Version 3.5a

Change in Dependent Variables

Version 4 has a comprehensive set of inductive formulations based on the magnetic vector potential. These cover all modeling situations except for situations with strongly nonlinear conductivity (superconductors) for which magnetic field H-based formulations are more suitable.

The 2D formulations based on the magnetic field H as dependent variable in version 3.5a are not yet included in version 4.1. A full set (3D, 2D and 2D axisymmetry) of H based formulations is planned for a future release.

Models created in version 3.5a that are built using an H based formulation will not include any physics interface settings when opened in version 4.1. Geometrical data and definitions (constants and expressions) will be imported and the physics can manually be added using the (vector potential based) Magnetic Fields physics interface.

Pair Boundary Conditions

The Contact Resistance, Transition, and Perfect Magnetic Conductor boundary conditions are not yet available as assembly Pair boundary conditions.

A new set of slit-based, discontinuous boundary conditions, which does not require assemblies is introduced in version 4. In most models, this can replace the assembly pair boundary condition.