DirichletBC

Imposes the essential boundary condition $var element = document.getElementById("moose-equation-9cfdfbeb-f2bb-485c-bdc7-5e158095440e");katex.render("u=g", element, {displayMode:false,throwOnError:false});$ , where $var element = document.getElementById("moose-equation-dbed3277-beef-41ee-919d-74b55f70b688");katex.render("g", element, {displayMode:false,throwOnError:false});$ is a constant, controllable value.

Description

DirichletBC is the simplest type of NodalBC, and is used for imposing so-called "essential" boundary conditions on systems of partial differential equations (PDEs). Such boundary conditions force a particular set of degrees of freedom (DOFs) defined by the boundary parameter to take on a single, controllable value. This class is appropriate to use for PDEs of the form

$var element = document.getElementById("moose-equation-f8535f92-e973-41b6-b06f-1f79a99ce327");katex.render("\\begin{aligned} -\\nabla^2 u &= f && \\quad \\in \\Omega \\\\ u &= g && \\quad \\in \\partial \\Omega_D \\\\ \\frac{\\partial u}{\\partial n} &= h && \\quad \\in \\partial \\Omega_N, \\end{aligned}", element, {displayMode:true,throwOnError:false});$

where $var element = document.getElementById("moose-equation-4272c9f7-f995-4d08-928f-11f6299d9e4c");katex.render("\\Omega \\subset \\mathbb{R}^n", element, {displayMode:false,throwOnError:false});$ is the domain, and $var element = document.getElementById("moose-equation-5900e982-f465-4b7c-808a-59ab48eff283");katex.render("\\partial \\Omega = \\partial \\Omega_D \\cup \\partial \\Omega_N", element, {displayMode:false,throwOnError:false});$ is its boundary. In this case, a DirichletBC object is used to impose the condition (2) on the subset of the boundary denoted by $var element = document.getElementById("moose-equation-cf173a43-110a-498c-b1f9-583f0e94be95");katex.render("\\partial \\Omega_D", element, {displayMode:false,throwOnError:false});$ . In this case, the value corresponds to the constant $var element = document.getElementById("moose-equation-15b4d4a9-02da-4974-88c2-f4cd2dfb26ea");katex.render("g", element, {displayMode:false,throwOnError:false});$ , and the user must define one or more sidesets corresponding to the boundary subset $var element = document.getElementById("moose-equation-2f5cc53f-081d-45c3-b262-5acefc419f95");katex.render("\\partial \\Omega_D", element, {displayMode:false,throwOnError:false});$ .

Preset boundary conditions

With the parameter preset = true, the value of the boundary condition is applied before the solve begins. With preset = false, the boundary condition is only enforced as the solve progresses. In most situations, presetting the boundary condition is better.

Similar Dirichlet BCs

To use a Function instead of a constant value : FunctionDirichletBC
To impose a Dirichlet BC using a penalty method or on an elemental variable : PenaltyDirichletBC
To use a another variable instead of a constant value : MatchedValueBC

Example Input Syntax

  [./right_v]
    type = DirichletBC
    variable = v
    boundary = 1
    value = 3
  [../]

Input Parameters

boundaryThe list of boundary IDs from the mesh where this object applies
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:The list of boundary IDs from the mesh where this object applies
valueValue of the BC
C++ Type:double
Unit:(no unit assumed)
Controllable:Yes
Description:Value of the BC
variableThe name of the variable that this residual object operates on
C++ Type:NonlinearVariableName
Unit:(no unit assumed)
Controllable:No
Description:The name of the variable that this residual object operates on

Required Parameters

diag_save_inThe name of auxiliary variables to save this BC'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>
Unit:(no unit assumed)
Controllable:No
Description:The name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)
displacementsThe displacements
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The displacements
presetTrueWhether or not to preset the BC (apply the value before the solve begins).
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether or not to preset the BC (apply the value before the solve begins).
save_inThe name of auxiliary variables to save this BC'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>
Unit:(no unit assumed)
Controllable:No
Description:The name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

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>
Unit:(no unit assumed)
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>
Unit:(no unit assumed)
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>
Unit:(no unit assumed)
Controllable:No
Description:The extra tags for the vectors this Kernel should fill
matrix_tagssystem timeThe tag for the matrices this Kernel should fill
Default:system time
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:nontime, system, time
Controllable:No
Description:The tag for the matrices this Kernel should fill
vector_tagsresidualThe tag for the vectors this Kernel should fill
Default:residual
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:nontime, time, residual
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>
Unit:(no unit assumed)
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Unit:(no unit assumed)
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
Unit:(no unit assumed)
Controllable:No
Description:Determines whether this object is calculated using an implicit or explicit form
seed0The seed for the master random number generator
Default:0
C++ Type:unsigned int
Unit:(no unit assumed)
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
Unit:(no unit assumed)
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

(moose/test/tests/bcs/matched_value_bc/matched_value_bc_test.i)

[Mesh]
  [./square]
    type = GeneratedMeshGenerator
    nx = 2
    ny = 2
    dim = 2
  [../]
[]

# Solves a pair of coupled diffusion equations where u=v on the boundary

[Variables]
  active = 'u v'

  [./u]
    order = FIRST
    family = LAGRANGE
    initial_condition = 3
  [../]

  [./v]
    order = FIRST
    family = LAGRANGE
    initial_condition = 2
  [../]
[]

[Kernels]
  active = 'diff_u diff_v'

  [./diff_u]
    type = Diffusion
    variable = u
  [../]

  [./diff_v]
    type = Diffusion
    variable = v
  [../]
[]

[BCs]
  active = 'right_v left_u'

  [./right_v]
    type = DirichletBC
    variable = v
    boundary = 1
    value = 3
  [../]

  [./left_u]
    type = MatchedValueBC
    variable = u
    boundary = 3
    v = v
  [../]
[]

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

[Executioner]
  type = Steady
  solve_type = 'NEWTON'

  petsc_options_iname = '-pc_type -pc_hypre_type'
  petsc_options_value = 'hypre boomeramg'

  nl_rel_tol = 1e-10
  l_tol = 1e-12
[]

[Outputs]
  file_base = out
  exodus = true
[]

Description
Preset boundary conditions
Similar Dirichlet BCs
Example Input Syntax
Input Parameters