Discussion Forum

I am working on a Magnetic Fields (mf) simulation in COMSOL, modeling a triaxial Helmholtz coil system. My goal is to extract the magnetic flux density components (Bx, By, Bz) at a grid of points inside a 25 mm cubic workspace that includes the region between the coils. I attempted to use the Cut Point 3D dataset to define these points and then evaluate the magnetic field components. However, many of these points return NaN (Not a Number) values when I try to extract Bx, By, Bz.

What I Tried

• The magnetic field visualization works correctly in the 3D plot, meaning Bx, By, Bz are computed somewhere in the solution.
• Point Evaluation works at mesh nodes, but Grid/Cut Point 3D Evaluation fails with NaN values.
• I realized that the cut points were being placed in regions between the coils, which do not seem to contain computed field values.
• The meshed regions include only the coils and a defined workspace, but the air between coils may not be included in the physics calculation.
• I have assigned materials (Air for the surrounding space), and the coils are current-driven.

Questions:

• Why does COMSOL return NaN values for Bx, By, Bz in the space between coils?
• How can I ensure that the magnetic flux density is computed and accessible in these regions?
• What is the best approach to extract Bx, By, Bz at a grid of points that includes the workspace and space between coils?

I would appreciate any insights or suggestions on how to resolve this issue. Thank you!