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

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

# BodyForce

## Description

`BodyForce`

implements a force term in momentum transport or structural mechanics or a source term in species/mass transport. The strong form, given a domain is defined as

(1) where is the source term (negative if a sink) and the second term on the left hand side represents the strong forms of other kernels. The `BodyForce`

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

(2) where the are the test functions, and are the trial solutions in the finite dimensional space for the unknown ().

The Jacobian term for this kernel is zero: , since it is assumed that is not** a function of the unknown .

The force is constructed through a user supplied constant , function value evaluated at the current time and quadrature point , and/or postprocessor value . The constant , supplied through the parameter `value`

, may also be controlled over the course of a transient simulation with a `Controls`

block. , , are supplied through the input parameters `value`

, `function`

, and `postprocessor`

respectively. Not supplying , , or through its corresponding parameter is equivalent to setting its value to unity.

## Example Syntax

The case below demonstrates the use of `BodyForce`

where the force term is supplied solely through the constant value (denoted by `value`

):

```
[Kernels]
active = 'bodyforce ie'
[./bodyforce]
type = BodyForce
variable = u
value = 10.0
[../]
[./ie]
type = TimeDerivative
variable = u
[../]
[]
```

(moose/test/tests/restart/restart_diffusion/restart_diffusion_transient_from_steady.i)## Input Parameters

- function1A function that describes the body force
Default:1

C++ Type:FunctionName

Description:A function that describes the body force

- value1Coefficent to multiply by the body force term
Default:1

C++ Type:double

Description:Coefficent to multiply by the body force term

- 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

- postprocessor1A postprocessor whose value is multiplied by the body force
Default:1

C++ Type:PostprocessorName

Description:A postprocessor whose value is multiplied by the body force

### 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