Model induction between two coils

[mrbearb]

Gotcha..

I'm working through a multiple coil version of what I showed earlier, but am having some divergence issues.

Here's what I've been able to get so far:

2Coilpotentail.png (9.09 KiB) Viewed 138 times

2Coilpotentail_WithMagField.png (202.68 KiB) Viewed 138 times

I increased the resolution of the mesh and am currently running the solvers, which as of right now is looking like it should converge (hopefully!)

However, and this is probably a newb-y question, but I would like to be able to know what the optimal resolution size that will be needed for a given mesh. How can I calculate the required mesh size that will lead to a converging solution? Is it better to just guess and check?

What are some other factors to consider in order to ensure that a solution converges..

Thanks again for all your help!

[kevinarden]

I do not know how to do that for coil solver and MagDyn. I do know how to for StressSolver, displacement, elastic response, etc.

Typically a convergence study works, keep refining, is the answer getting better or unchanging. Eventually it will make no appreciable difference and then the mesh is as fine as it needs to be.

This is an example of multiple coils

https://github.com/ElmerCSC/elmer-elmag ... /FiveCoils

[mrbearb]

I see.. thank you for your help.

I'm now having issues with what I think may be a non-conformal mesh or my sif being not setup correctly..

This is what I am seeing with a closed coil:

StreamTracer.png (123.23 KiB) Viewed 111 times

MagFieldGlyph.png (114.29 KiB) Viewed 111 times

As you might be able to see, the stream tracer (top picture) is contained solely within the coil itself despite changing the position of the reference.
Also, the Magnetic field strength (bottom) drops off to nearly zero just outside of the coil..

I used gmsh to create the mesh and set the size very small around the coil, CoilSolver to generate the current, and MagDyn and MagDynPost to generate the mag field vectors. I was expecting to see the fields continue strongly through the area surrounding the coil, but that is not what I'm getting.

Any help would be greatly appreciated!

[kevinarden]

Can you post the geo file

[mrbearb]

Here's my geo file.. I build the cad model and import it into gmsh to create the mesh

[Rich_B]

Hello,

To check for a conforming mesh, add this statement to the simulation section of a sif:

Desired Mesh Pieces = 1

then running with your mesh, ElmerSolver reports an error and exits:

CalculateMeshPieces: Number of separate pieces in mesh is 2
ERROR:: CalculateMeshPieces: Number of pieces differ from the requested 1

Next, edit your geo file to add this statement at the end:

//+
Coherence;

Run ElmerSolver again and now there is one mesh piece:

CalculateMeshPieces: Number of separate pieces in mesh is 1

Rich.

[mrbearb]

Hi Rich,

thanks for the tip. I tried this, but it seems like the coherence command has removed the distinction between the two volumes that I would like to have in my mesh. It gave what looks like a coherent mesh, but I am no longer able to assign different material properties to my coil and to the surrounding area.. Any thoughts?

[Rich_B]

Hello,

Just a guess, maybe try commenting out the 'Physical' commands, and use the body and boundary numbers in the sif. Loading the mesh in ElmerGUI after commenting out the 'Physicals' gave two bodies and 12 boundaries.

Rich.

[mrbearb]

Liftoff!

Removing the physical commands, while making it a bit more tedious within ElmerGui, I now have a coherent mesh and successful test case for a cylindrical coil..

Now, on to two coils and the induction

Stay tuned

success_magfieldlines.png (379.56 KiB) Viewed 42 times

[mrbearb]

Ok, update time..

CurrentDensity.png (392.64 KiB) Viewed 38 times

I have both coils in the simulation, but am not able to any current being induced onto the second non-driven coil..

Here's my sif:

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) = 1
  Solver Input File = case.sif
  Post File = case.vtu
  Calculate Mesh Pieces = True
  Desired Mesh Pieces = 1
End

Constants
  Gravity(4) = 0 -1 0 9.82
  Stefan Boltzmann = 5.670374419e-08
  Permittivity of Vacuum = 8.85418781e-12
  Permeability of Vacuum = 1.25663706e-6
  Boltzmann Constant = 1.380649e-23
  Unit Charge = 1.6021766e-19
End

Body 1
  Target Bodies(1) = 1
  Name = "CoilBody1"
  Equation = 1
  Material = 1
  Body Force = 1
End

Body 2
  Target Bodies(1) = 2
  Name = "CoilBody2"
  Equation = 2
  Material = 1
  Initial condition = 1
End

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

Solver 3
  Equation = MgDynPost
  Calculate Electric Field = True
  Procedure = "MagnetoDynamics" "MagnetoDynamicsCalcFields"
  Calculate Magnetic Field Strength = True
  Calculate Current Density = True
  Skip Nodal Fields = False
  Exec Solver = Always
  Stabilize = True
  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 = CoilSolver
  Desired Current Density = 1
  Coil Center(3) = 0 0 0
  Coil Normal(3) = 1 0 0
  Procedure = "CoilSolver" "CoilSolver"
  Fix Input Current Density = True
  Calculate Nodal Fields = True
  Coil Closed = True
  Normalize Coil Current = True
  Desired Coil Current = 10000
  Narrow Interface = True
  Exec Solver = Always
  Stabilize = True
  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 = 2000
  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 2
  Equation = MgDyn
  Fix Input Current Density = True
  Use Elemental CoilCurrent = True
  Procedure = "MagnetoDynamics" "WhitneyAVSolver"
  Exec Solver = Always
  Stabilize = True
  Optimize Bandwidth = True
  Steady State Convergence Tolerance = 1.0e-6
  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 = 10000
  Linear System Convergence Tolerance = 1.0e-10
  BiCGstabl polynomial degree = 6
  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 = "ActiveEquation"
  Active Solvers(3) = 3 1 2
End

Equation 2
  Name = "PassiveEquation"
  Active Solvers(2) = 2 3
End

Material 1
  Name = "Copper (generic)"
  Sound speed = 3810.0
  Relative Permeability = 0.999994
  Heat Conductivity = 401.0
  Heat Capacity = 385.0
  Density = 8960.0
  Youngs modulus = 115.0e9
  Heat expansion Coefficient = 16.5e-6
  Electric Conductivity = 59.59e6
  Poisson ratio = 0.34
End

Material 2
  Name = "Air (room temperature)"
  Relative Permittivity = 1.00059
  Heat Capacity = 1005.0
  Heat Conductivity = 0.0257
  Sound speed = 343.0
  Viscosity = 1.983e-5
  Relative Permeability = 1.00000037
  Density = 1.205
  Heat expansion Coefficient = 3.43e-3
End

Material 3
  Name = "Iron (generic)"
  Sound speed = 5000.0
  Heat Capacity = 449.0
  Heat expansion Coefficient = 11.8e-6
  Poisson ratio = 0.29
  Electric Conductivity = 10.30e6
  Youngs modulus = 193.053e9
  Density = 7870.0
  Heat Conductivity = 80.2
  Relative Permeability = 6000
End

Body Force 1
  Name = "Source"
  Current Density 2 = Equals "CoilCurrent e 2"
  Current Density 3 = Equals "CoilCurrent e 3"
  Current Density 1 = Equals "CoilCurrent e 1"
End

Initial Condition 1
  Name = "InitialCondition 2"
  AV {e} = 0
  AV = 0
End

Boundary Condition 1
  Target Boundaries(6) = 13 14 15 16 17 18 
  Name = "BoxCondition"
  AV = 0
  AV {e} = 0
End

I have compared my sif to the TEAM7 example here: https://github.com/ElmerCSC/elmer-elmag ... /README.md
But, I don't see any induced current as I would expect there to be.