A multi-physics issue about the tutorial "csg_to_cad".

[PixelRonald]

Hello, all.
I am following the tutorial "csg_to_cad"https://cardinal.cels.anl.gov/tutorials/csg_to_cad.html and trying to couple the solid mechanics to simulate the heat expansion. Here are my test codes (I'm a beginner of Cardinal and MOOSE, so there may be some syntax errors)
fuel.i.txt
openmc.i.txt
and the mechanics.i:

[Mesh]
  [fuel]
    type = FileMeshGenerator
    file = krusty_full.e
  []
[]
[GlobalParams]
  displacements = 'disp_x disp_y disp_z'
[]
[Problem]
	kernel_coverage_check = false
	material_coverage_check = false
[]
[AuxVariables]
  [T]
    block = '2'
    initial_condition = 1073.15
  []
[]
[Physics/SolidMechanics/QuasiStatic]
  [all]
    add_variables = true
    automatic_eigenstrain_names = true
    block = '2'
  []
[]
[Materials]
	[elasticity]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = 8.8e10
    poissons_ratio = 0.35
    block = '2'
	[]
  [expansion]
    type = ComputeThermalExpansionEigenstrain
    temperature = T
    stress_free_temperature = 273.15    
    thermal_expansion_coeff = 2.0895e-5
    eigenstrain_name = thermal_expansion
    block = '2'
  []
  [stress]
    type = ComputeLinearElasticStress
    block = '2'
  []
[]
[BCs]
  [fixed_heatpipes_x]
    type = DirichletBC
    boundary = 'heat_pipes'
    value = 0
    variable = disp_x 
  []
  [fixed_heatpipes_y]
    type = DirichletBC
    boundary = 'heat_pipes'
    value = 0
    variable = disp_y 
  []
  [fixed_heatpipes_z]
    type = DirichletBC
    boundary = 'heat_pipes'
    value = 0
    variable = disp_z
  []
  [fixed_bottom_z]
    type = DirichletBC
    boundary = 'bottom'
    value = 0
    variable = disp_z
  []
  [fixed_top_z]
    type = DirichletBC
    boundary = 'top'
    value = 0
    variable = disp_z 
  []
[]
[Postprocessors]
	[initial_vol]
		type = VolumePostprocessor
		use_displaced_mesh = false
		execute_on = 'initial'
		block = '2'
	[]
	[mech_volume]
		type = VolumePostprocessor
		use_displaced_mesh = true
		execute_on = 'initial timestep_end'
		block = '2'
	[]
	[vol_change_rate]
		type = ParsedPostprocessor
		expression = 'mech_volume / initial_vol'
		pp_names = 'mech_volume initial_vol'
	[]
[]
[Executioner]
  type = Transient
  solve_type = NEWTON
  petsc_options_iname = '-pc_type'
  petsc_options_value = 'lu'
[]
[Outputs]
  exodus = true
[]

The codes aren't finished yet, there are some problems exist. I want only the block fuel (block '2') to do heat conduction and expansion calculations, while other parts remain unchanged. And I also want to get the flux tally of the entire model. So is this feasible, if it is, how should I do?
And here are model files:
model (1).xml
krusty.zip

[aprilnovak]

Hi @PixelRonald, apologies for the delay as a lot of our team was on travel last week at the Physor conference. Taking a look now!

[aprilnovak]

tagging @MendesMichael @meltawila

[PixelRonald]

Hi @aprilnovak, do you have any suggestions on this problem?

[aprilnovak]

Hi @PixelRonald, @MendesMichael is taking a look and will help out soon! Thanks @MendesMichael

[MendesMichael]

Hello @PixelRonald, your overall structure does makes sense.

Since you did not uploaded any error messages is kinda hard to find exactly what could be wrong, but I do have some suggestions:

Regarding the flux tally over everything, what you currently have is already doing that.

In your openmc.i file, It might be a good idea to explicitly declare your fuel_density variable in AuxVariable and block restrict it to block=2. I also noticed that you have conflicting AuxKernels on fuel_density. You have both a FunctionAux and a CellDensityAux writing to the same variable.

In your displacement variables (disp_x, disp_y, and disp_z) I believe you should also block restrict it.

In regards your mechanics.i file you might be over constraining, since you have top and bottom fixed, you might have a huge internal stresses and your simulation might fail, but since I have not ran your files I cannot confirm that 100%, if you have any convergence problem you might want to relax these BCs. You could try symmetry boundary conditions at the fuel center, allowing free expansion at both ends.

If you find any errors during your simulation, feel free to paste them here and we can try to help you out.