# 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
[../]
[]


## Input Parameters

• variableThe name of the variable that this Kernel operates on

C++ Type:NonlinearVariableName

Options:

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

### Required Parameters

• function1A function that describes the body force

Default:1

C++ Type:FunctionName

Options:

Description:A function that describes the body force

• blockThe list of block ids (SubdomainID) that this object will be applied

C++ Type:std::vector

Options:

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

• value1Coefficent to multiply by the body force term

Default:1

C++ Type:double

Options:

Description:Coefficent to multiply by the body force term

• postprocessor1A postprocessor whose value is multiplied by the body force

Default:1

C++ Type:PostprocessorName

Options:

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

Options:

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

Options:

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

Options:

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

Options:

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

Options:

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

Options:

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

Options:

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

• vector_tagsnontimeThe tag for the vectors this Kernel should fill

Default:nontime

C++ Type:MultiMooseEnum

Options:nontime time

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

Options:

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

Options:nontime system

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

Options:

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