Magnetodynamics Solver, wrong magnetic field strength?

Numerical methods and mathematical models of Elmer
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Bavragor
Posts: 32
Joined: 07 Nov 2013, 14:10
Antispam: Yes

Magnetodynamics Solver, wrong magnetic field strength?

Post by Bavragor »

Hi community,

I have a problem with an electromagnetic model. The model describes a single wire surrounded by air and and an iron cylinder (picture). The solution of the magnetic field strength is lower at increasing distance to the wire than it should be (f.e. r=50mm -> H=1450A/m instead of 2500A/m or r=100mm -> H=200A/m instead of 1250A/m).

Anyone an idea what i have done wrong?


SIF-file:

Code: Select all

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

Simulation
  Max Output Level = 10
  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 = sw_fine.sif
  Post File = sw_fine.ep
Coordinate Scaling = 1e-3
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 1"
  Equation = 1
  Material = 1
  Body Force = 1
End

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

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

Solver 2
  Equation = MgDyn
  Variable = AV
  Fix Input Current Density = True
  Procedure = "MagnetoDynamics" "WhitneyAVSolver"
  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 = CG
  Linear System Max Iterations = 5000
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 2
  Linear System Preconditioning = Diagonal
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = False
  Linear System Residual Output = 1
  Linear System Precondition Recompute = 1
End

Solver 3
  Equation = MgDynPost
  Calculate Magnetic Field Strength = True
  Potential Variable = AV
  Procedure = "MagnetoDynamics" "MagnetoDynamicsCalcFields"
  Calculate Electric Field = True
  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 = CG
  Linear System Max Iterations = 5000
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 2
  Linear System Preconditioning = Diagonal
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = False
  Linear System Residual Output = 1
  Linear System Precondition Recompute = 1
End

Solver 1
  Equation = Static Current Conduction
  Calculate Volume Current = True
  Variable = Potential
  Procedure = "StatCurrentSolve" "StatCurrentSolver"
  Exec Solver = Before Simulation
  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 = CG
  Linear System Max Iterations = 5000
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 2
  Linear System Preconditioning = Diagonal
  Linear System ILUT Tolerance = 1.0e-3
  Linear System Abort Not Converged = False
  Linear System Residual Output = 1
  Linear System Precondition Recompute = 1
End

Solver 4
  Equation = Result Output
  Procedure = "ResultOutputSolve" "ResultOutputSolver"
  Output Format = Vtu
  Output File Name = sw_fine
  Exec Solver = After Timestep
End

Equation 1
  Name = "Wire"
  Active Solvers(4) = 2 3 1 4
End

Equation 2
  Name = "Core+Air"
  Active Solvers(3) = 2 3 4
End

Material 1
  Name = "Copper"
  Electric Conductivity = 59.59e6
  Porosity Model = Always saturated
  Density = 8960.0
  Relative Permeability = 1
End

Material 2
  Name = "Steel"
  Electric Conductivity = 1.449e6
  Porosity Model = Always saturated
  Density = 7850.0
  Relative Permeability = 1000
End

Material 3
  Name = "Air"
  Electric Conductivity = 0
  Porosity Model = Always saturated
  Density = 1.205
  Relative Permeability = 1
End

Body Force 1
  Name = "BodyForce 1"
  Current Density 1 = Equals Volume Current 1
  Current Density 3 = Equals Volume Current 3
  Current Density 2 = Equals Volume Current 2
End

Boundary Condition 1
  Target Boundaries(1) = 8 
  Name = "Ground"
  Potential = 0
End

Boundary Condition 2
  Target Boundaries(1) = 2 
  Name = "Current"
  Current Density = 1e7
End

Boundary Condition 3
  Target Boundaries(3) = 1 7 10 
  Name = "Border"
  AV {e} = 0
End
Attachments
model.png
model.png (131.1 KiB) Viewed 1971 times
Last edited by Bavragor on 26 Apr 2016, 11:25, edited 1 time in total.
Bavragor
Posts: 32
Joined: 07 Nov 2013, 14:10
Antispam: Yes

Re: Magnetodynamics Solver, wrong magnetic field strength?

Post by Bavragor »

Some additional information:

wire:
r=5mm
l=100mm

core:
r=10mm
R=100mm
l=100mm

boundary:
r=120mm
l=120mm

The assigned boundary is only the lateral area of the outer cylinder.
If someone want the project files, I will upload them.
kataja
Posts: 74
Joined: 09 May 2014, 16:06
Antispam: Yes

Re: Magnetodynamics Solver, wrong magnetic field strength?

Post by kataja »

Hi

I think you might be missing a keyword "electric current density" on the wire ends (BCs 1 and 2) that is used to tell the AV solver what should be the current at the boundary. If its not given, the Helmholtz projected input current might look unexpected (see around pp. 86 in the Elmer Models Manual).

-Juhani
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