- variableThe name of the variable that this Kernel operates on
C++ Type:NonlinearVariableName

Description:The name of the variable that this Kernel operates on

- vThe coupled variable which provides the force
C++ Type:std::vector

Description:The coupled variable which provides the force

# CoupledForce

## Description

`CoupledForce`

implements a source term within the domain proportional to a coupled variable: (1) where is a known scalar coefficient, is a coupled unknown value, and the second term on the left hand side corresponds to the strong forms of other kernels. In a species transport context, the value can be regarded as a reaction rate coefficient.

The weak form, in inner-product notation, is defined as

(2) where are the test functions and is the finite element solution of the weak formulation.

The corresponding Jacobian is (3)

## Example Syntax

The kernel block below shows a variable that is diffusing and being produced at a rate proportional to the concentration of a variable which is also diffusing.

```
[Kernels]
[./diff_u]
type = Diffusion
variable = u
[../]
[./coupled_force_u]
type = CoupledForce
variable = u
v = v
[../]
[./diff_v]
type = Diffusion
variable = v
[../]
[]
```

(moose/test/tests/bcs/coupled_dirichlet_bc/coupled_dirichlet_bc.i)In this example the input parameter "coef" that corresponds to is omitted. In this case the "coef" value defaults to one.

## Input Parameters

- blockThe list of block ids (SubdomainID) that this object will be applied
C++ Type:std::vector

Description:The list of block ids (SubdomainID) that this object will be applied

- coef1Coefficent ($\sigma$) multiplier for the coupled force term.
Default:1

C++ Type:double

Description:Coefficent ($\sigma$) multiplier for the coupled force term.

### 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 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

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.)

- 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 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

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.)

- 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