Input spatial data of "alpha" into Van Genuchten capillary model

[zhx999]

Hi there,

In PorousFlow module, the Van Genuchten capillarity model is defined with two coefficients "alpha" and "m".

I understand that in the scripts "PorousFlowCapillaryPressureVG.h" and "PorousFlowCapillaryPressureVG.C" under UserObject, the alpha is set to be a single value as input.

If I want to include a file which contains the spatial data of alpha, like the heterogeneous permeability. Is there any simple way to include it?

[GiudGiud]

Hello

You can modify the source code to use alpha as a function or as an auxiliary variable.
This should not be too difficult if you have followed the tutorial and created your own object once

Guillaume

[cpgr]

Check out https://github.com/idaholab/moose/blob/next/modules/porous_flow/src/userobjects/PorousFlowCapillaryPressureBC.C for an example where the entry pressure pe can be a variable or a Real.

[cpgr]

Sorry - scratch that! I mustn't have pushed that change but have it locally somewhere. I'll try and find it 😄

[zhx999]

Sorry - scratch that! I mustn't have pushed that change but have it locally somewhere. I'll try and find it 😄

Looking forward to the commit. Thanks again for the discussion, very helpful!

[cpgr]

So, what I had done is basically what you have here. I copied your code, compiled and ran a test and it seems to work ok.

[Mesh]
  type = GeneratedMesh
  dim = 1
  nx = 100
[]

[GlobalParams]
  PorousFlowDictator = dictator
[]

[Variables]
  [p0]
    initial_condition = 1e6
  []
  [s1]
  []
[]

[AuxVariables]
  [s0aux]
    family = MONOMIAL
    order = CONSTANT
  []
  [s1aux]
    family = MONOMIAL
    order = CONSTANT
  []
  [p0aux]
    family = MONOMIAL
    order = CONSTANT
  []
  [p1aux]
    family = MONOMIAL
    order = CONSTANT
  []
  [alpha]
    family = MONOMIAL
    order = CONSTANT
  []
[]

[AuxKernels]
  [s0]
    type = PorousFlowPropertyAux
    property = saturation
    phase = 0
    variable = s0aux
  []
  [s1]
    type = PorousFlowPropertyAux
    property = saturation
    phase = 1
    variable = s1aux
  []
  [p0]
    type = PorousFlowPropertyAux
    property = pressure
    phase = 0
    variable = p0aux
  []
  [p1]
    type = PorousFlowPropertyAux
    property = pressure
    phase = 1
    variable = p1aux
  []
[]

[ICs]
  [alpha]
    type = RandomIC
    variable = alpha
    min = 1e-5
    max = 1e-4
  []
[]

[Kernels]
  [p0]
    type = Diffusion
    variable = p0
  []
  [s1]
    type = Diffusion
    variable = s1
  []
[]

[UserObjects]
  [dictator]
    type = PorousFlowDictator
    porous_flow_vars = 'p0 s1'
    number_fluid_phases = 2
    number_fluid_components = 2
  []
  [pc]
    type = PorousFlowCapillaryPressureVG_alpha
    alpha = alpha
    m = 0.5
    sat_lr = 0.1
    log_extension = false
  []
[]

[Materials]
  [temperature]
    type = PorousFlowTemperature
  []
  [ppss]
    type = PorousFlow2PhasePS
    phase0_porepressure = p0
    phase1_saturation = s1
    capillary_pressure = pc
  []
  [kr0]
    type = PorousFlowRelativePermeabilityVG
    phase = 0
    m = 0.5
  []
  [kr1]
    type = PorousFlowRelativePermeabilityCorey
    phase = 1
    n = 2
  []
[]

[VectorPostprocessors]
  [vpp]
    type = ElementValueSampler
    variable = 's0aux s1aux p0aux p1aux alpha'
    sort_by = id
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
  nl_abs_tol = 1e-6
[]

[BCs]
  [sleft]
    type = DirichletBC
    variable = s1
    value = 0
    boundary = left
  []
  [sright]
    type = DirichletBC
    variable = s1
    value = 1
    boundary = right
  []
[]

[Outputs]
  csv = true
  execute_on = timestep_end
[]

[zhx999]

Hello,

Thank you for the great insight.

I realize that I forgot to set one optional parameter log_extension = false.

  [pc]
    type = PorousFlowCapillaryPressureVG_alpha
    alpha = alpha
    m = 0.5
    sat_lr = 0.1
    log_extension = false
  []

Which already stated in the document:

Since it's optional parameter so I didn't pay attention to it. Now the simulation can run properly.

Thanks a lot!