[Magnetostatic] different results for FEMM and Elmer

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Markus_eyP
Posts: 5
Joined: 14 Apr 2020, 17:52
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[Magnetostatic] different results for FEMM and Elmer

Post by Markus_eyP »

Hello,

I try to simulate the magnetix flux density B of two parallel arranged magnets (Nd, N52). Magnetization in the same direction and perpendicular to the axis connecting both magnets . I did it with FEMM and Elmer and got different results for the strength of B. That is in the middle between both magnets 530mT for FEMM (non-linear H-B curve) and 400 mT for Elmer (non-linear) respectively 430 mT for Elemer (linear). Magnet properties are taken from FEMM. Does someone has experience with both programs and knows the problem? Thanks

.vtu-file is attached and following the Elmer sif-file. H-B curve is in a separate file.

Code: Select all

Header
  CHECK KEYWORDS Warn
  Mesh DB "." "."
  Include Path ""
  Results Directory ""
End

Simulation
  Max Output Level = 5
  Coordinate System = Cartesian
  Coordinate Mapping(3) = 1 2 3
  Simulation Type = Steady state
  Steady State Max Iterations = 1
  Output Intervals = 1
  Timestepping Method = BDF
  BDF Order = 1
  Solver Input File = case.sif
  Post File = case.vtu
End

Constants
  Gravity(4) = 0 -1 0 9.82
  Stefan Boltzmann = 5.67e-08
  Permittivity of Vacuum = 8.8542e-12
  Boltzmann Constant = 1.3807e-23
  Unit Charge = 1.602e-19
End

Body 1
  Target Bodies(1) = 1
  Name = "Body Property 1"
  Equation = 1
  Material = 3
End

Body 2
  Target Bodies(1) = 2
  Name = "Body Property 2"
  Equation = 1
  Material = 3
End

Body 3
  Target Bodies(1) = 3
  Name = "Body Property 3"
  Equation = 1
  Material = 1
End

Solver 2
  Equation = MgDyn2DPost
  Procedure = "MagnetoDynamics2D" "BSolver"
  Exec Solver = Always
  Stabilize = True
  Bubbles = False
  Lumped Mass Matrix = False
  Optimize Bandwidth = True
  Steady State Convergence Tolerance = 1.0e-5
  Nonlinear System Convergence Tolerance = 1.0e-7
  Nonlinear System Max Iterations = 20
  Nonlinear System Newton After Iterations = 3
  Nonlinear System Newton After Tolerance = 1.0e-3
  Nonlinear System Relaxation Factor = 1
  Linear System Solver = Iterative
  Linear System Iterative Method = BiCGStab
  Linear System Max Iterations = 500
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 2
  Linear System Preconditioning = ILU0
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = False
  Linear System Residual Output = 10
  Linear System Precondition Recompute = 1
End

Solver 1
  Equation = MgDyn2D
  Procedure = "MagnetoDynamics2D" "MagnetoDynamics2D"
  Variable = Potential
  Exec Solver = Always
  Stabilize = True
  Bubbles = False
  Lumped Mass Matrix = False
  Optimize Bandwidth = True
  Steady State Convergence Tolerance = 1.0e-5
  Nonlinear System Convergence Tolerance = 1.0e-7
  Nonlinear System Max Iterations = 20
  Nonlinear System Newton After Iterations = 3
  Nonlinear System Newton After Tolerance = 1.0e-3
  Nonlinear System Relaxation Factor = 1
  Linear System Solver = Iterative
  Linear System Iterative Method = BiCGStab
  Linear System Max Iterations = 500
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 2
  Linear System Preconditioning = ILU0
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = False
  Linear System Residual Output = 10
  Linear System Precondition Recompute = 1
End

Equation 1
  Name = "MgDyn2D"
  Active Solvers(2) = 2 1
End

Equation 2
  Name = "MgDyn2DPost"
End

Material 1
  Name = "Air"
  Relative Permeability = 1
End

Material 2
  Name = "N52"
  Relative Permeability = 1.05
  Magnetization 1 = 956180
  Electric Conductivity = 0.667
  H-B Curve = Variable "nonlin"
    include HB_N52
  End
End

Boundary Condition 1
  Target Boundaries(1) = 3 
  Name = "FarField"
  Infinity BC = True
End
Markus
Attachments
case_t0001.zip
(592.62 KiB) Downloaded 289 times
mika
Posts: 230
Joined: 15 Sep 2009, 07:44

Re: [Magnetostatic] different results for FEMM and Elmer

Post by mika »

I'm not familiar with FEMM. Anyhow, how sensitive is the result with respect to the BC on the outer surface or on the location of this surface? Do the two models have the same BC on the outer surface?

-- Mika
Markus_eyP
Posts: 5
Joined: 14 Apr 2020, 17:52
Antispam: Yes

Re: [Magnetostatic] different results for FEMM and Elmer

Post by Markus_eyP »

Thanks for your answer Mika. I calculated again and got different results to the previously posted ones. Too much open windows last time. :?

FEMM | Elmer | H-B curve
- | 457mT | linear
530mT | 517mT | non-linear

So not that spectacular anymore, but some slight difference I can live with. Maybe they are really due to different BC. FEMM generates a shell of 7 boundaries per default.
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