## Potential & Electric Current just in specific bodies

General discussion about Elmer
MFeMult
Posts: 6
Joined: 11 Sep 2017, 16:36
Antispam: Yes

### Potential & Electric Current just in specific bodies

Hey all,

In brief:
I have multiple Domains (14 bodies) in a simulation and I want to apply the potential/joule heating JUST in three bodies (domains).
However, the heat flux shall propagate through every domain and lead to thermal stresses in the overall structure.

I like to set up the following:
1. potential/electric field evolves an electric current
2. electric current results in liberated heat by joule heating
3. the liberated heat drives the thermal expansion und results in thermal stresses

I do need to say, that I reviewed multiple examples for elmer. [e.g. Tutorial 9: Thermal actuator driven with electrostatic currents, http://www.nic.funet.fi/index/elmer/doc ... nonGUI.pdf, 2017.Sept.11]
However, I did not find any example that explains how to.
I know it must be pretty simple - nevertheless I'd appreciate if someone could give me a hint...

Cheers
Manuel

Code: Select all

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

Simulation
Max Output Level = 5
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Transient
Steady State Max Iterations = 10 !1 is weak coupling, 10 is strong couling
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 2
Timestep intervals = 2	! is the overall time
Timestep Sizes = 1e-1		! is the time step size
Solver Input File = case.sif
Post File = case.vtu
End

Constants
Gravity(4) = 0 0 0 9.82
Stefan Boltzmann = 5.67e-08
! Permittivity Of Vacuum = 8.8542e-12 ! C^2/Nm^2
Permittivity Of Vacuum = 1.0 ! manipulation for conducting material
Boltzmann Constant = 1.3807e-23
Unit Charge = 1.602e-19
End

Body 1
Target Bodies(3) = 1 2 3
Equation = 1
Material = 1
Body Force = 1
Initial condition = 1
End

Body 2
Target Bodies(2) = 7 14
Equation = 1
Material = 2
Initial condition = 2
End

Body 3
Target Bodies(3) = 4 5 6
Equation = 1
Material = 3
Initial condition = 2
End

Body 4
Target Bodies(6) = 8 9 10 11 12 13
Equation = 1
Material = 4
Initial condition = 2
End

Material 1
Electric Conductivity = Variable Temperature
Real
298.0 0.62500e5
398.0 0.82500e5
End
Heat expansion Coefficient = 20.0e-6
Heat Conductivity = 3.4
Relative Permittivity = 1.0005
Heat Capacity = 1278.0
Mesh Poisson ratio = 0.35
Density = 2780.0
Poisson ratio = 0.35
Youngs modulus = 7.405e9
End

Material 2
Electric Conductivity = Variable Temperature
Real
298.0 0.62500e5
398.0 0.82500e5
End
Heat expansion Coefficient = 21.0e-6
Heat Conductivity = 730
Heat Capacity = 921.0
Mesh Poisson ratio = 0.33
Density = 2700.0
Poisson ratio = 0.33
Youngs modulus = 70.0e9
End

Material 3
Electric Conductivity = Variable Temperature
Real
298.0 0.62500e5
398.0 0.82500e5
End
Heat expansion Coefficient = 21.0e-6
Heat Conductivity = 1.0
Heat Capacity = 921.0
Mesh Poisson ratio = 0.33
Density = 2700.0
Poisson ratio = 0.33
Youngs modulus = 70.0e9
End

Material 4
Electric Conductivity = Variable Temperature
Real
298.0 0.62500e5
398.0 0.82500e5
End
Heat expansion Coefficient = 3.43e-6 ! e-3 is normal, but looks crazy. change does not effect significantly
Heat Conductivity = 0.0257
Heat Capacity = 1005.0
!Mesh Poisson ratio = 0.33
Density = 1205.0
Poisson ratio = 0.33
Youngs modulus = 1.0e5
End

Initial Condition 1
Potential = 0
Displacement 1 = 0
Displacement 2 = 0
Displacement 3 = 0
Temperature = 298
End

Initial Condition 2
Displacement 1 = 0
Displacement 2 = 0
Displacement 3 = 0
Temperature = 298
End

Body Force 1
Heat Source = Equals Joule Heating
End

Boundary Condition 1
Target Boundaries(2) = 1 2
Name = "Sym"
Heat Flux = 0
Displacement 1 = 0
End

Boundary Condition 2
Target Boundaries(3) = 3 5 7
Name = "TopPot"
Potential = 30.7
End

Boundary Condition 3
Target Boundaries(3) = 4 6 8
Name = "BotPot"
Potential = 0.0
End

Boundary Condition 4
Target Boundaries(2) = 9 10
Name = "Boun"
Displacement 3 = 0
Temperature = 298
End

Equation 1
Active Solvers(4) = 1 2 3 4
End

Solver 1
Equation = Result Output
Output Format = Vtu
Output File Name = case
Procedure = "ResultOutputSolve" "ResultOutputSolver"
Exec Solver = Always
End

Solver 2
Equation = Stat Current Solver
Procedure = "StatCurrentSolve" "StatCurrentSolver"
Variable = Potential
Variable DOFs = 1
Calculate Joule Heating = True
Calculate Electric Conductivity = True
Linear System Solver = Iterative
Linear System Iterative Method = CG
Linear System Preconditioning = ILU3
Linear System Max Iterations = 300
Linear System Convergence Tolerance = 1.0e-8
Nonlinear System Max Iterations = 1
Nonlinear System Convergence Tolerance = 1.0-6
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-12
Nonlinear System Relaxation Factor = 1.0
Steady State Convergence Tolerance = 1.0e-6
End

Solver 3
Equation = Heat Equation
Variable = Temperature
Variable DOFs = 1
!Calculate Joule Heating = True
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Preconditioning = ILU1
Linear System Max Iterations = 350
Linear System Convergence Tolerance = 1.0e-9
Nonlinear System Max Iterations = 1
Nonlinear System Convergence Tolerance = 1.0e-07
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-12
Nonlinear System Relaxation Factor = 0.5
Steady State Convergence Tolerance = 1.0e-07
End

Solver 4
Equation = Stress Analysis
Linear System Solver = Direct
Variable = Displacement
Variable Dofs = 3
Calculate Stresses = True
Linear System Iterative Method = "BiCGStab"
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-08
Linear System Abort Not Converged = True
Linear System Preconditioning = "ILU0"
Linear System Residual Output = 1
Steady State Convergence Tolerance = 1.0e-05
Nonlinear System Convergence Tolerance = 1.0e-05
Nonlinear System Max Iterations = 1
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-02
Nonlinear System Relaxation Factor = 1
Linear System Precondition Recompute = 1
End


mzenker
Posts: 1729
Joined: 07 Dec 2009, 11:49
Location: Germany

### Re: Potential & Electric Current just in specific bodies

Hi,

I did not quite get where your problem is. What happens when you run the simulation?

Difficult to say if there is a mistake just from the sif file. But at least, if you have 14 bodies, they must all figure in the sif and have materials assigned.

In general, if you are new to Elmer, you could start with a sif file generated by ElmerGUI and only go on to write the sif file from scratch if you are more experienced and if you want to do things that are not possible with the GUI.

HTH,

Matthias

MFeMult
Posts: 6
Joined: 11 Sep 2017, 16:36
Antispam: Yes

### Re: Potential & Electric Current just in specific bodies

Hey Matthias,

thnx for your reply.

1. My problem is/was that the differential equation of
$(1) \textbf{E} = -\nabla \phi$\\
$(2) \textbf{j} = \frac{1}{\varrho}\cdot\textbf{E}$
were solved in every body/domain. That was not my intent.
However, I misinterpreted the meaning of Equation, body and interaction with solvers.
After I added a second equation (so that I had two), I solved it correctly.
Now it seems absolutely clear and I don't know why I didn't see it before.

Code: Select all

Equation 1
Name = "elec-therm-mech"
Calculate Stresses = True
Active Solvers(4) = 4 3 2 1
End

Equation 2
Name = "therm-mech"
Calculate Stresses = True
Active Solvers(2) = 3 2
End

2.
But at least, if you have 14 bodies, they must all figure in the sif and have materials assigned.
Fore sure, that must be the case. However, thnx for pointing out.

3.
In general, if you are new to Elmer, you could start with a sif file generated by ElmerGUI and only go on to write the sif file from scratch
if you are more experienced and if you want to do things that are not possible with the GUI.
Well, yes and no. My main aim is to understand how things work... So I started from the scratch -> however, I do need to say, that your hint helped because it is solved Thnx

Cheers Matthias,
Manuel

mzenker
Posts: 1729
Joined: 07 Dec 2009, 11:49
Location: Germany

### Re: Potential & Electric Current just in specific bodies

Hmmm...

If you solver numbering didn't change, the above means that you solver for heat and current everywhere, and for stress only in a part of your domain. And you have result output only where you solver for stress. Is that what you wanted?

Also I would set

Exec Solver = After Timestep

for result output.

Matthias