Magnetic circuit reluctance may be calculated as Rm = Um / Flux,
where Rm - magnetic circuit resistance
Um = Integral(HdL) - magnetic voltage drop,
Flux - magnetic flux across the cross-section.
In case of uniform magnetic flux distribution the magnetic circuit reluctance can be calculated as
Rm = (1/μμ0) · L / S
The magnetic circuit analysis can be performed by the same methods as the electric circuit analysis. This approach is suitable for simple geometry and uniform flux distribution.
For complex core construction and non-linear materials the FEA approach is more appropriate. Depending on the problem formulation, you can use DC, AC or Transient Magnetics module of QuickField to calculate the magnetic circuit reluctance of the core.