InterfaceReaction

Description

Specie M transports between two domains (domain 1 and domain 2), at the interface consider the following reaction is taking place:

$var element = document.getElementById("moose-equation-8b73726d-7c21-460d-81b6-2bd28dfb9861");katex.render("M(1)\\xrightleftharpoons[k_b]{k_f}M(2)", element, {displayMode:true,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$

With the first order reaction rate assuming a quasi-steady-state

$var element = document.getElementById("moose-equation-d5ecced5-bf89-4935-b69a-4af575416887");katex.render("Reaction Rate = \\frac {\\partial C_1} {\\partial t} = k_f C_1 - k_b C_2 \\approx 0", element, {displayMode:true,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$

where $var element = document.getElementById("moose-equation-b27e3ef0-63aa-4b6d-abff-0ad9be7a4a47");katex.render("C_1", element, {displayMode:false,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$ is the specie concentration in domain 1, $var element = document.getElementById("moose-equation-d3d10725-2424-43e7-8386-b46772ae04d1");katex.render("C_2", element, {displayMode:false,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$ is the specie concentration in domain 2, $var element = document.getElementById("moose-equation-7c53d254-d213-4db6-a656-5395557a6a7d");katex.render("k_f", element, {displayMode:false,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$ is the forward reaction coefficient, and $var element = document.getElementById("moose-equation-91dc12c6-a721-45c0-952c-1525d0663fc1");katex.render("k_b", element, {displayMode:false,throwOnError:false,macros:{"\\eqc":"\\,,","\\eqp":"\\,.","\\pd":"\\frac{\\partial #1}{\\partial #2}","\\pr":"\\left(#1\\right)","\\ddt":"\\frac{d #1}{d t}"}});$ is the backward reaction coefficient. InterfaceReaction object is used to impose this condition. Associated kernel is:

(framework/src/interfacekernels/InterfaceReaction.C)

(framework/include/interfacekernels/InterfaceReaction.h)

In addition, fluxes are matched from both domains, this could be achieved by InterfaceDiffusion.

Both kernels at the interface work together to give full mathematical and physical meaning of the problem.

Two examples (steady-state and transient-state) are shown in the MOOSE test directory,

(test/tests/interfacekernels/1d_interface/reaction_1D_steady.i)

(test/tests/interfacekernels/1d_interface/reaction_1D_transient.i)

Example Input Syntax

  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]

Input Parameters

kbBackward reaction rate coefficient.
C++ Type:double
Controllable:No
Description:Backward reaction rate coefficient.
kfForward reaction rate coefficient.
C++ Type:double
Controllable:No
Description:Forward reaction rate coefficient.
neighbor_varThe variable on the other side of the interface.
C++ Type:std::vector<VariableName>
Controllable:No
Description:The variable on the other side of the interface.
variableThe name of the variable that this residual object operates on
C++ Type:NonlinearVariableName
Controllable:No
Description:The name of the variable that this residual object operates on

Required Parameters

boundaryThe list of boundaries (ids or names) from the mesh where this object applies
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:The list of boundaries (ids or names) from the mesh where this object applies
prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Controllable:No
Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Optional Parameters

absolute_value_vector_tagsThe tags for the vectors this residual object should fill with the absolute value of the residual contribution
C++ Type:std::vector<TagName>
Controllable:No
Description:The tags for the vectors this residual object should fill with the absolute value of the residual contribution
extra_matrix_tagsThe extra tags for the matrices this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the matrices this Kernel should fill
extra_vector_tagsThe extra tags for the vectors this Kernel should fill
C++ Type:std::vector<TagName>
Controllable:No
Description:The extra tags for the vectors this Kernel should fill
matrix_tagssystemThe tag for the matrices this Kernel should fill
Default:system
C++ Type:MultiMooseEnum
Options:nontime, system
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagsnontimeThe tag for the vectors this Kernel should fill
Default:nontime
C++ Type:MultiMooseEnum
Options:nontime, time
Controllable:No
Description:The tag for the vectors this Kernel should fill

Tagging Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
diag_save_inThe name of auxiliary variables to save this Kernel's diagonal Jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)
C++ Type:std::vector<AuxVariableName>
Controllable:No
Description:The name of auxiliary variables to save this Kernel's diagonal Jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)
diag_save_in_var_sideThis parameter must exist if diag_save_in variables are specified and must have the same length as diag_save_in. This vector specifies whether the corresponding aux_var should save-in jacobian contributions from the primary ('p') or secondary side ('s').
C++ Type:MultiMooseEnum
Options:m, s
Controllable:No
Description:This parameter must exist if diag_save_in variables are specified and must have the same length as diag_save_in. This vector specifies whether the corresponding aux_var should save-in jacobian contributions from the primary ('p') or secondary side ('s').
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:Yes
Description:Set the enabled status of the MooseObject.
implicitTrueDetermines whether this object is calculated using an implicit or explicit form
Default:True
C++ Type:bool
Controllable:No
Description:Determines whether this object is calculated using an implicit or explicit form
save_inThe name of auxiliary variables to save this Kernel's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)
C++ Type:std::vector<AuxVariableName>
Controllable:No
Description:The name of auxiliary variables to save this Kernel's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)
save_in_var_sideThis parameter must exist if save_in variables are specified and must have the same length as save_in. This vector specifies whether the corresponding aux_var should save-in residual contributions from the primary ('p') or secondary side ('s').
C++ Type:MultiMooseEnum
Options:m, s
Controllable:No
Description:This parameter must exist if save_in variables are specified and must have the same length as save_in. This vector specifies whether the corresponding aux_var should save-in residual contributions from the primary ('p') or secondary side ('s').
seed0The seed for the master random number generator
Default:0
C++ Type:unsigned int
Controllable:No
Description:The seed for the master random number generator
use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Advanced Parameters

Input Files

(test/tests/postprocessors/interface_diffusive_flux/interface_diffusive_flux.i)
(test/tests/interfacekernels/1d_interface/reaction_1D_transient.i)
(test/tests/interfacekernels/1d_interface/reaction_1D_steady.i)

(framework/src/interfacekernels/InterfaceReaction.C)

// This file is part of the MOOSE framework
// https://www.mooseframework.org
//
// All rights reserved, see COPYRIGHT for full restrictions
// https://github.com/idaholab/moose/blob/master/COPYRIGHT
//
// Licensed under LGPL 2.1, please see LICENSE for details
// https://www.gnu.org/licenses/lgpl-2.1.html

#include "InterfaceReaction.h"

registerMooseObject("MooseApp", InterfaceReaction);

InputParameters
InterfaceReaction::validParams()
{
  InputParameters params = InterfaceKernel::validParams();
  params.addRequiredParam<Real>("kf", "Forward reaction rate coefficient.");
  params.addRequiredParam<Real>("kb", "Backward reaction rate coefficient.");
  params.addClassDescription("Implements a reaction to establish ReactionRate=k_f*u-k_b*v "
                             "at interface.");
  return params;
}

InterfaceReaction::InterfaceReaction(const InputParameters & parameters)
  : InterfaceKernel(parameters), _kf(getParam<Real>("kf")), _kb(getParam<Real>("kb"))
{
}

Real
InterfaceReaction::computeQpResidual(Moose::DGResidualType type)
{
  Real r = 0;
  switch (type)
  {
    // Move all the terms to the LHS to get residual, for primary domain
    // Residual = kf*u - kb*v = kf*u - kb*v
    // Weak form for primary domain is: (test, kf*u - kb*v)
    case Moose::Element:
      r = _test[_i][_qp] * (_kf * _u[_qp] - _kb * _neighbor_value[_qp]);
      break;

    // Similarly, weak form for secondary domain is: -(test, kf*u - kb*v),
    // flip the sign because the direction is opposite.
    case Moose::Neighbor:
      r = -_test_neighbor[_i][_qp] * (_kf * _u[_qp] - _kb * _neighbor_value[_qp]);
      break;
  }
  return r;
}

Real
InterfaceReaction::computeQpJacobian(Moose::DGJacobianType type)
{
  Real jac = 0;
  switch (type)
  {
    case Moose::ElementElement:
      jac = _test[_i][_qp] * _kf * _phi[_j][_qp];
      break;
    case Moose::NeighborNeighbor:
      jac = -_test_neighbor[_i][_qp] * -_kb * _phi_neighbor[_j][_qp];
      break;
    case Moose::NeighborElement:
      jac = -_test_neighbor[_i][_qp] * _kf * _phi[_j][_qp];
      break;
    case Moose::ElementNeighbor:
      jac = _test[_i][_qp] * -_kb * _phi_neighbor[_j][_qp];
      break;
  }
  return jac;
}

(framework/include/interfacekernels/InterfaceReaction.h)

// This file is part of the MOOSE framework
// https://www.mooseframework.org
//
// All rights reserved, see COPYRIGHT for full restrictions
// https://github.com/idaholab/moose/blob/master/COPYRIGHT
//
// Licensed under LGPL 2.1, please see LICENSE for details
// https://www.gnu.org/licenses/lgpl-2.1.html

#pragma once

#include "InterfaceKernel.h"

/**
 * Implements a reaction to establish ReactionRate=k_f*u-k_b*v
 * at interface.
 */
class InterfaceReaction : public InterfaceKernel
{
public:
  static InputParameters validParams();

  InterfaceReaction(const InputParameters & parameters);

protected:
  virtual Real computeQpResidual(Moose::DGResidualType type) override;
  virtual Real computeQpJacobian(Moose::DGJacobianType type) override;

  /// Forward reaction rate coefficient
  Real _kf;

  /// Backward reaction rate coefficient
  Real _kb;
};

(test/tests/interfacekernels/1d_interface/reaction_1D_steady.i)

# Steady-state test for the InterfaceReaction kernel.
#
# Specie M transport from domain 1 (0<=x<=1) to domain 2 (1<x<=2),
# u and v are concentrations in domain 1 and domain 2.
#
# Diffusion in both domains can be described by Ficks law and diffusion
# kernel is applied.
#
# Specie M has different diffusity in different domains, here set as D1=4, D2=2.
#
# Dirichlet boundary conditions are applied, i.e., u(0)=1, v(2)=0
#
# At the interface consider the following
#
# (a) Fluxes are matched from both domains (InterfaceDiffusion kernel)
#
# (b) First-order reaction is R = kf*u - kb*v
#
# Analytical solution is
# u = -0.2*u+1,    0<=u<=1
# v = -0.4*v+0.8,  1<v<=2

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 1
    nx = 10
    xmax = 2
  []
  [./subdomain1]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '1.0 0 0'
    block_id = 1
    top_right = '2.0 1.0 0'
  [../]
  [./interface]
    type = SideSetsBetweenSubdomainsGenerator
    input = 'subdomain1'
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'primary0_interface'
  [../]
[]

[Variables]
  [./u]
    order = FIRST
    family = LAGRANGE
    block = '0'
  [../]
  [./v]
    order = FIRST
    family = LAGRANGE
    block = '1'
  [../]
[]

[Kernels]
  [./diff_u]
    type = MatDiffusion
    variable = u
    block = '0'
    diffusivity = D
  [../]
  [./diff_v]
    type = MatDiffusion
    variable = v
    block = '1'
    diffusivity = D
  [../]
[]

[InterfaceKernels]
  [./interface]
    type = InterfaceDiffusion
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    D = D
    D_neighbor = D
  [../]
  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = 'left'
    value = 1
  [../]
  [./right]
    type = DirichletBC
    variable = v
    boundary = 'right'
    value = 0
  [../]
[]

[Materials]
  [./block0]
    type = GenericConstantMaterial
    block = '0'
    prop_names = 'D'
    prop_values = '4'
  [../]
  [./block1]
    type = GenericConstantMaterial
    block = '1'
    prop_names = 'D'
    prop_values = '2'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Steady
  solve_type = PJFNK
  nl_rel_tol = 1e-10
[]

[Outputs]
  print_linear_residuals = true
  execute_on = 'FINAL'
  exodus = true
  csv = true
[]

[Debug]
  show_var_residual_norms = true
[]

[Postprocessors]
  [./elemental_error_u]
    type = ElementL2Error
    function = -0.2*x+1
    variable = 'u'
    block = '0'
  [../]
  [./elemental_error_v]
    type = ElementL2Error
    function = -0.4*x+0.8
    variable = 'v'
    block = '1'
  [../]
[]

(test/tests/interfacekernels/1d_interface/reaction_1D_transient.i)

# Transient-state test for the InterfaceReaction kernel.
#
# Same to steady-state, except the following
#
# Natural BCs are applied (i.e. NewmannBC h=0 at left and right)

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 1
    nx = 10
    xmax = 2
  []
  [./subdomain1]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '1.0 0 0'
    block_id = 1
    top_right = '2.0 1.0 0'
  [../]
  [./interface]
    type = SideSetsBetweenSubdomainsGenerator
    input = 'subdomain1'
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'primary0_interface'
  [../]
[]

[Variables]
  [./u]
    order = FIRST
    family = LAGRANGE
    block = '0'
  [../]
  [./v]
    order = FIRST
    family = LAGRANGE
    block = '1'
  [../]
[]

[Kernels]
  [./diff_u]
    type = MatDiffusion
    diffusivity = D
    variable = u
    block = '0'
  [../]
  [./diff_v]
    type = MatDiffusion
    diffusivity = D
    variable = v
    block = '1'
  [../]
  [./diff_u_dt]
    type = TimeDerivative
    variable = u
    block = '0'
  [../]
  [./diff_v_dt]
    type = TimeDerivative
    variable = v
    block = '1'
  [../]
  [./source_u]
    type = BodyForce
    variable = u
    block = '0'
  [../]
[]

[InterfaceKernels]
  [./interface]
    type = InterfaceDiffusion
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    D = D
    D_neighbor = D
  [../]
  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]
[]

[Materials]
  [./block0]
    type = GenericConstantMaterial
    block = '0'
    prop_names = 'D'
    prop_values = '4'
  [../]
  [./block1]
    type = GenericConstantMaterial
    block = '1'
    prop_names = 'D'
    prop_values = '2'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 10
  dt = 0.1
  solve_type = NEWTON
[]

[Outputs]
  exodus = true
  print_linear_residuals = true
[]

[Debug]
  show_var_residual_norms = true
[]

(test/tests/interfacekernels/1d_interface/reaction_1D_steady.i)

# Steady-state test for the InterfaceReaction kernel.
#
# Specie M transport from domain 1 (0<=x<=1) to domain 2 (1<x<=2),
# u and v are concentrations in domain 1 and domain 2.
#
# Diffusion in both domains can be described by Ficks law and diffusion
# kernel is applied.
#
# Specie M has different diffusity in different domains, here set as D1=4, D2=2.
#
# Dirichlet boundary conditions are applied, i.e., u(0)=1, v(2)=0
#
# At the interface consider the following
#
# (a) Fluxes are matched from both domains (InterfaceDiffusion kernel)
#
# (b) First-order reaction is R = kf*u - kb*v
#
# Analytical solution is
# u = -0.2*u+1,    0<=u<=1
# v = -0.4*v+0.8,  1<v<=2

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 1
    nx = 10
    xmax = 2
  []
  [./subdomain1]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '1.0 0 0'
    block_id = 1
    top_right = '2.0 1.0 0'
  [../]
  [./interface]
    type = SideSetsBetweenSubdomainsGenerator
    input = 'subdomain1'
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'primary0_interface'
  [../]
[]

[Variables]
  [./u]
    order = FIRST
    family = LAGRANGE
    block = '0'
  [../]
  [./v]
    order = FIRST
    family = LAGRANGE
    block = '1'
  [../]
[]

[Kernels]
  [./diff_u]
    type = MatDiffusion
    variable = u
    block = '0'
    diffusivity = D
  [../]
  [./diff_v]
    type = MatDiffusion
    variable = v
    block = '1'
    diffusivity = D
  [../]
[]

[InterfaceKernels]
  [./interface]
    type = InterfaceDiffusion
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    D = D
    D_neighbor = D
  [../]
  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = 'left'
    value = 1
  [../]
  [./right]
    type = DirichletBC
    variable = v
    boundary = 'right'
    value = 0
  [../]
[]

[Materials]
  [./block0]
    type = GenericConstantMaterial
    block = '0'
    prop_names = 'D'
    prop_values = '4'
  [../]
  [./block1]
    type = GenericConstantMaterial
    block = '1'
    prop_names = 'D'
    prop_values = '2'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Steady
  solve_type = PJFNK
  nl_rel_tol = 1e-10
[]

[Outputs]
  print_linear_residuals = true
  execute_on = 'FINAL'
  exodus = true
  csv = true
[]

[Debug]
  show_var_residual_norms = true
[]

[Postprocessors]
  [./elemental_error_u]
    type = ElementL2Error
    function = -0.2*x+1
    variable = 'u'
    block = '0'
  [../]
  [./elemental_error_v]
    type = ElementL2Error
    function = -0.4*x+0.8
    variable = 'v'
    block = '1'
  [../]
[]

(test/tests/postprocessors/interface_diffusive_flux/interface_diffusive_flux.i)

postprocessor_type = InterfaceDiffusiveFluxAverage

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 6
    xmax = 3
    ny = 9
    ymax = 3
    elem_type = QUAD4
  []
  [subdomain_id]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '0 0 0'
    top_right = '2 1 0'
    block_id = 1
  []
  [interface]
    input = subdomain_id
    type = SideSetsBetweenSubdomainsGenerator
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'interface'
  []
[]

[Functions]
  [fn_exact]
    type = ParsedFunction
    expression = 'x*x+y*y'
  []
[]

[Variables]
  [u]
    block = 0
  []
  [v]
    block = 1
  []
[]


[Kernels]
  [diff_u]
    type = Diffusion
    variable = u
  []
  [body_u]
    type = BodyForce
    variable = u
    function = 1
  []

  [diff_v]
    type = Diffusion
    variable = v
  []
  [body_v]
    type = BodyForce
    variable = v
    function = -1
  []
[]

# Not a diffusion interface but can test the postprocessor anyway
[InterfaceKernels]
  [reaction]
    type = InterfaceReaction
    kb = 1
    kf = 2
    variable = u
    neighbor_var = v
    boundary = 'interface'
  []
[]

[BCs]
  [all]
    type = FunctionDirichletBC
    variable = u
    boundary = '0 1 2 3'
    function = fn_exact
  []
[]

[Postprocessors]
  [diffusive_flux]
    type = ${postprocessor_type}
    variable = u
    neighbor_variable = v
    diffusivity = 1
    execute_on = TIMESTEP_END
    boundary = 'interface'
  []
[]

[Executioner]
  type = Steady
  solve_type = NEWTON
[]

[Outputs]
  file_base = ${raw ${postprocessor_type} _fe}
  exodus = true
[]

(test/tests/interfacekernels/1d_interface/reaction_1D_transient.i)

# Transient-state test for the InterfaceReaction kernel.
#
# Same to steady-state, except the following
#
# Natural BCs are applied (i.e. NewmannBC h=0 at left and right)

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 1
    nx = 10
    xmax = 2
  []
  [./subdomain1]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '1.0 0 0'
    block_id = 1
    top_right = '2.0 1.0 0'
  [../]
  [./interface]
    type = SideSetsBetweenSubdomainsGenerator
    input = 'subdomain1'
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'primary0_interface'
  [../]
[]

[Variables]
  [./u]
    order = FIRST
    family = LAGRANGE
    block = '0'
  [../]
  [./v]
    order = FIRST
    family = LAGRANGE
    block = '1'
  [../]
[]

[Kernels]
  [./diff_u]
    type = MatDiffusion
    diffusivity = D
    variable = u
    block = '0'
  [../]
  [./diff_v]
    type = MatDiffusion
    diffusivity = D
    variable = v
    block = '1'
  [../]
  [./diff_u_dt]
    type = TimeDerivative
    variable = u
    block = '0'
  [../]
  [./diff_v_dt]
    type = TimeDerivative
    variable = v
    block = '1'
  [../]
  [./source_u]
    type = BodyForce
    variable = u
    block = '0'
  [../]
[]

[InterfaceKernels]
  [./interface]
    type = InterfaceDiffusion
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    D = D
    D_neighbor = D
  [../]
  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]
[]

[Materials]
  [./block0]
    type = GenericConstantMaterial
    block = '0'
    prop_names = 'D'
    prop_values = '4'
  [../]
  [./block1]
    type = GenericConstantMaterial
    block = '1'
    prop_names = 'D'
    prop_values = '2'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient
  num_steps = 10
  dt = 0.1
  solve_type = NEWTON
[]

[Outputs]
  exodus = true
  print_linear_residuals = true
[]

[Debug]
  show_var_residual_norms = true
[]

(test/tests/interfacekernels/1d_interface/reaction_1D_steady.i)

# Steady-state test for the InterfaceReaction kernel.
#
# Specie M transport from domain 1 (0<=x<=1) to domain 2 (1<x<=2),
# u and v are concentrations in domain 1 and domain 2.
#
# Diffusion in both domains can be described by Ficks law and diffusion
# kernel is applied.
#
# Specie M has different diffusity in different domains, here set as D1=4, D2=2.
#
# Dirichlet boundary conditions are applied, i.e., u(0)=1, v(2)=0
#
# At the interface consider the following
#
# (a) Fluxes are matched from both domains (InterfaceDiffusion kernel)
#
# (b) First-order reaction is R = kf*u - kb*v
#
# Analytical solution is
# u = -0.2*u+1,    0<=u<=1
# v = -0.4*v+0.8,  1<v<=2

[Mesh]
  [gen]
    type = GeneratedMeshGenerator
    dim = 1
    nx = 10
    xmax = 2
  []
  [./subdomain1]
    input = gen
    type = SubdomainBoundingBoxGenerator
    bottom_left = '1.0 0 0'
    block_id = 1
    top_right = '2.0 1.0 0'
  [../]
  [./interface]
    type = SideSetsBetweenSubdomainsGenerator
    input = 'subdomain1'
    primary_block = '0'
    paired_block = '1'
    new_boundary = 'primary0_interface'
  [../]
[]

[Variables]
  [./u]
    order = FIRST
    family = LAGRANGE
    block = '0'
  [../]
  [./v]
    order = FIRST
    family = LAGRANGE
    block = '1'
  [../]
[]

[Kernels]
  [./diff_u]
    type = MatDiffusion
    variable = u
    block = '0'
    diffusivity = D
  [../]
  [./diff_v]
    type = MatDiffusion
    variable = v
    block = '1'
    diffusivity = D
  [../]
[]

[InterfaceKernels]
  [./interface]
    type = InterfaceDiffusion
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    D = D
    D_neighbor = D
  [../]
  [./interface_reaction]
    type = InterfaceReaction
    variable = u
    neighbor_var = 'v'
    boundary = 'primary0_interface'
    kf = 1 # Forward reaction rate coefficient
    kb = 2 # Backward reaction rate coefficient
  [../]
[]

[BCs]
  [./left]
    type = DirichletBC
    variable = u
    boundary = 'left'
    value = 1
  [../]
  [./right]
    type = DirichletBC
    variable = v
    boundary = 'right'
    value = 0
  [../]
[]

[Materials]
  [./block0]
    type = GenericConstantMaterial
    block = '0'
    prop_names = 'D'
    prop_values = '4'
  [../]
  [./block1]
    type = GenericConstantMaterial
    block = '1'
    prop_names = 'D'
    prop_values = '2'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Steady
  solve_type = PJFNK
  nl_rel_tol = 1e-10
[]

[Outputs]
  print_linear_residuals = true
  execute_on = 'FINAL'
  exodus = true
  csv = true
[]

[Debug]
  show_var_residual_norms = true
[]

[Postprocessors]
  [./elemental_error_u]
    type = ElementL2Error
    function = -0.2*x+1
    variable = 'u'
    block = '0'
  [../]
  [./elemental_error_v]
    type = ElementL2Error
    function = -0.4*x+0.8
    variable = 'v'
    block = '1'
  [../]
[]

Description
Example Input Syntax
Input Parameters
Input Files