MgDyn: Trivially zero solution

[OscarS]

Hi,

I am trying to familiarize with Gmsh for geometry and Elmer for electromagnetic (and eventually also thermal) FEA, such that later I will be able to design a three-phase transformer.
I have been playing around with some examples, and now I am trying to start setting up a model that gets a bit closer to the product I will be working on. I think I made to create a geometry and mesh its volumes using Gmsh (.msh file attached); consisting of three ferromagnetic cores, one coil, and an air sphere around this assembly. The next step would be to solve this problem while applying an arbitrary current to the coil (in this case 100A is used as input), and I would like to output magnetic field strength and/or magnetic flux density.
However, when solving this problem the solver output is "Solution trivially zero!". I have been trying altering various settings, but no positive result and I am getting a bit lost.
Also tried with two different solvers: Static current Conduction, or Coil Solver. In both cases no proper result.
In the attachment the .sif file, and the mesh file of the domain are included. Note; mesh is made a bit coarser in this model to be able to attach it with the limited file size.

[kevinarden]

MGDYN Post is going first so there is no solution to calculate fields from so it reports Solution Trivially zero
Need to make MGDYN solver 1 to create the solution
then MGDYN POST can run

viewtopic.php?t=8184

[OscarS]

Thanks for the quick support!
What you are saying makes quit a lot of sense yes, thanks:)
I tried to alter the sif file accordingly, but it seems not to solve the issue..? At least, after altering the outcome still is the same.

In the attachment the adjusted sif file.

Below the solver log:


ELMER SOLVER (v 9.0) STARTED AT: 2024/01/12 11:43:06
ParCommInit: Initialize #PEs: 1
MAIN:
MAIN: =============================================================
MAIN: ElmerSolver finite element software, Welcome!
MAIN: This program is free software licensed under (L)GPL
MAIN: Copyright 1st April 1995 - , CSC - IT Center for Science Ltd.
MAIN: Webpage http://www.csc.fi/elmer, Email elmeradm@csc.fi
MAIN: Version: 9.0 (Rev: Release, Compiled: 2022-08-02)
MAIN: Running one task without MPI parallelization.
MAIN: Running with just one thread per task.
MAIN: Lua interpreter linked in.
MAIN: =============================================================

MAIN:
MAIN:
MAIN: -------------------------------------
MAIN: Reading Model: case.sif
LoadInputFile: Scanning input file: case.sif
LoadInputFile: Scanning only size info
LoadInputFile: First time visiting
LoadInputFile: Reading base load of sif file
LoadInputFile: Loading input file: case.sif
LoadInputFile: Reading base load of sif file
LoadInputFile: Number of BCs: 1
LoadInputFile: Number of Body Forces: 1
LoadInputFile: Number of Initial Conditions: 0
LoadInputFile: Number of Materials: 3
LoadInputFile: Number of Equations: 2
LoadInputFile: Number of Solvers: 3
LoadInputFile: Number of Bodies: 5
WARNING:: LoadInputFile: > Body Force 1 < not used in any Body!
ListTagKeywords: Setting weight for keywords!
ListTagKeywords: No parameters width suffix: normalize by area
ListTagKeywords: Setting weight for keywords!
ListTagKeywords: No parameters width suffix: normalize by volume

ElmerAsciiMesh: Base mesh name: ./.

LoadMesh: Elapsed REAL time: 1.3200 (s)

MAIN: -------------------------------------
AddVtuOutputSolverHack: Adding ResultOutputSolver to write VTU output in file: case

OptimizeBandwidth: ---------------------------------------------------------

OptimizeBandwidth: Computing matrix structure for: mgdyn...done.
OptimizeBandwidth: Half bandwidth without optimization: 34002
OptimizeBandwidth:

OptimizeBandwidth: Bandwidth Optimization ...done.
OptimizeBandwidth: Half bandwidth after optimization: 1619
OptimizeBandwidth: ---------------------------------------------------------

CoilSolver_int: Computing elemental field as only that can be fixed!

OptimizeBandwidth: ---------------------------------------------------------

OptimizeBandwidth: Computing matrix structure for: coilsolver...done.
OptimizeBandwidth: Half bandwidth without optimization: 6044
OptimizeBandwidth:

OptimizeBandwidth: Bandwidth Optimization ...done.
OptimizeBandwidth: Half bandwidth after optimization: 146
OptimizeBandwidth: ---------------------------------------------------------

OptimizeBandwidth: ---------------------------------------------------------

OptimizeBandwidth: Computing matrix structure for: mgdynpost...done.
OptimizeBandwidth: Half bandwidth without optimization: 6044
OptimizeBandwidth:
OptimizeBandwidth: Bandwidth Optimization ...done.
OptimizeBandwidth: Half bandwidth after optimization: 376
OptimizeBandwidth: ---------------------------------------------------------

ElmerSolver: Number of timesteps to be saved: 1

MAIN:
MAIN: -------------------------------------
MAIN: Steady state iteration: 1
MAIN: -------------------------------------
MAIN:

WhitneyAVSolver: Solving the AV equations with edge elements

MGDynAssembly: Elapsed REAL time: 0.2970 (s)

SolveLinearSystem: Solution trivially zero!

ComputeChange: SS (ITER=1) (NRM,RELC): ( 0.0000000 0.0000000 ) :: mgdyn

CoilSolver: --------------------------------------
CoilSolver: Solving current distribution in a coil
CoilSolver: --------------------------------------
CoilSolver: Assuming that all coils are closed!

CoilSolver: Choosing narrow fixing nodes for set: 1

CoilSolver: Choosing narrow fixing nodes for set: 2

CoilSolver: Set1 : 39 +nodes and 38 -nodes
CoilSolver: Set2 : 40 +nodes and 42 -nodes
CoilSolver: Computing the dummy potential field

10 0.3021E-02

20 0.1052E-02

30 0.4737E-03

40 0.3548E-03

50 0.3381E-03

60 0.2462E-04

70 0.1496E-06

78 0.6344E-10

ComputeChange: NS (ITER=1) (NRM,RELC): ( 0.58019404 2.0000000 ) :: coilsolver
CoilSolver: Initial coil current for coil 1: 9.1198E+03
CoilSolver: Coil potential multiplier: 1.0965E-04

10 0.1607E-02

20 0.5432E-03

30 0.1793E-04

40 0.5404E-04

50 0.4058E-05

60 0.1191E-05

70 0.1490E-06

79 0.8961E-10

ComputeChange: NS (ITER=2) (NRM,RELC): ( 0.57975005 0.76554901E-03 ) :: coilsolver
CoilSolver: Initial coil current for coil 1: 9.1249E+03
CoilSolver: Coil potential multiplier: 1.0959E-04

5 0.1136E-11

4 0.9786E-10

5 0.8202E-12

6 0.1057E-11

4 0.9786E-10

5 0.8202E-12

CoilSolver: Finding fixing potential for elemental current density!

10 0.1850E+00

20 0.5880E-01

30 0.1586E-01

40 0.1547E-01

50 0.2273E-01

60 0.3998E-02

70 0.1159E-02

80 0.3639E-05

87 0.4387E-10

CoilSolver: Fixing elemental current density to be divergence free!

CoilSolver: --------------------------------------
ComputeChange: SS (ITER=1) (NRM,RELC): ( 0.63619464E-04 2.0000000 ) :: coilsolver

MagnetoDynamicsCalcFields: Computing postprocessed fields

WARNING:: GetPermittivity: Permittivity not defined in material, defaulting to that of vacuum

SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!

SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
SolveLinearSystem: Solution trivially zero!
MagnetoDynamicsCalcFields: Eddy current power: 0.000000E+00
MagnetoDynamicsCalcFields: ElectroMagnetic Field Energy: 0.000000E+00
ResultOutputSolver: -------------------------------------
ResultOutputSolver: Saving with prefix: case
ResultOutputSolver: Creating list for saving - if not present
CreateListForSaving: Field Variables for Saving

ResultOutputSolver: Saving in unstructured VTK XML (.vtu) format
VtuOutputSolver: Saving results in VTK XML format with prefix: case
VtuOutputSolver: Saving number of partitions: 1

ResultOutputSolver: -------------------------------------
ElmerSolver: *** Elmer Solver: ALL DONE ***

ElmerSolver: The end
SOLVER TOTAL TIME(CPU,REAL): 3.46 3.46
ELMER SOLVER FINISHED AT: 2024/01/12 11:43:10

[kevinarden]

Try

Solver 3
Equation = MgDynPost
Calculate Current Density = True
Calculate Magnetic Field Strength = True
Procedure = "MagnetoDynamics" "MagnetoDynamicsCalcFields"
Calculate Electric Field = True
Exec Solver = After Saving

[OscarS]

I tried that one too, but the results is the same

[kevinarden]

OK I will take a harder look

[kevinarden]

You have a mesh issue. The bodies inside the air sphere do not know about the air sphere because they do not share nodes.

mesh.png

(497.11 KiB) Not downloaded yet

See page 61 chapter 9

https://www.nic.funet.fi/pub/sci/physic ... dElmer.pdf