# MatchedValueBC

Implements a NodalBC which equates two different Variables' values on a specified boundary.

## Description

MatchedValueBC is a NodalBC which applies to systems of two or more variables, and can be used to impose equality of two solutions along a given boundary. This class is appropriate for systems of partial differential equations (PDEs) of the form (1) where is the domain, and is its boundary, , are the unknowns, , are forcing functions (which may depend on both and ), and and are given fluxes. The v parameter is used to specify the variable whose value is tied to . In the example below, the other variable's name happens to be v as well.

## Example Input Syntax

  [./left_u]
type = MatchedValueBC
variable = u
boundary = 1
v = v
[../]
(moose/test/tests/bcs/matched_value_bc/matched_value_bc_test.i)

## Input Parameters

• variableThe name of the variable that this boundary condition applies to

C++ Type:NonlinearVariableName

Description:The name of the variable that this boundary condition applies to

• boundaryThe list of boundary IDs from the mesh where this boundary condition applies

C++ Type:std::vector

Description:The list of boundary IDs from the mesh where this boundary condition applies

• vThe variable whose value we are to match.

C++ Type:std::vector

Description:The variable whose value we are to match.

### Required Parameters

• 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

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.)

• 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

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.)

### Optional Parameters

• control_tagsAdds user-defined labels for accessing object parameters via control logic.

C++ Type:std::vector

Description:Adds user-defined labels for accessing object parameters via control logic.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

• implicitTrueDetermines whether this object is calculated using an implicit or explicit form

Default:True

C++ Type:bool

Description:Determines whether this object is calculated using an implicit or explicit form

• 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

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.

• vector_tagsresidualThe tag for the vectors this Kernel should fill

Default:residual

C++ Type:MultiMooseEnum

Description:The tag for the vectors this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

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

Description:The tag for the matrices this Kernel should fill

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Description:The extra tags for the matrices this Kernel should fill