- 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

# VectorNeumannBC

Imposes the integrated boundary condition , where is a user-defined, constant vector.

## Description

`VectorNeumannBC`

is an `IntegratedBC`

which weakly imposes the flux boundary condition , where the user specifies the vector and the unit normal vector is determined by the geometry of the domain . This class is appropriate to use in systems of partial differential equations (PDEs) of the form (1)

There is not a 1:1 correspondence between the choice of and the resulting solution, since the component of which is orthogonal to the outward normal vector will not have any effect on the result.

This class exists mainly for convenience: if the true solution has a constant flux, then it is easier to specify Neumann boundary conditions on parts of the boundary with different outward normal vectors by simply specifying the true constant flux vector, and allowing MOOSE to dot it with the appropriate outward normals as necessary.

## Example Input Syntax

```
[./top]
type = VectorNeumannBC
variable = u
vector_value = '1 1 0'
boundary = 2
[../]
```

(moose/test/tests/bcs/misc_bcs/vector_neumann_bc_test.i)## Input Parameters

- vector_value0 0 0vector this BC should act in
Default:0 0 0

C++ Type:libMesh::VectorValue

Description:vector this BC should act in

### Optional Parameters

- enableTrueSet the enabled status of the MooseObject.
Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

- 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.)

- 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.

- 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.

- seed0The seed for the master random number generator
Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

- 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.)

- 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

### Advanced Parameters

- vector_tagsnontimeThe tag for the vectors this Kernel should fill
Default:nontime

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_tagssystemThe tag for the matrices this Kernel should fill
Default:system

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