# MassEigenKernel

## Description

MassEigenKernel is used in the context of solving eigenvalue problems of the form

(1)

where represents the eigenvalue and represents the eigenvector. Kernels that inherit from EigenKernel like MassEigenKernel are grouped into the term and have their residual contributions multiplied by the eigenvalue . Consider the equation below

(2)

where is some reaction coefficient that accounts for loss of . The terms on the LHS of Eq. 2 are equivalent to the LHS of Eq. 1 and similarly for the right hand sides.

## Example Syntax

The kernels describing Eq. 2 are shown in the Kernel block below

[Kernels]
active = 'diff rea rhs'

[./diff]
type = Diffusion
variable = u
use_displaced_mesh = true
[../]

[./rea]
type = CoefReaction
variable = u
coefficient = 2.0
use_displaced_mesh = true
[../]

[./rhs]
type = MassEigenKernel
variable = u
use_displaced_mesh = true
[../]
[]
(test/tests/executioners/eigen_executioners/ipm.i)

The syntax for MassEigenKernel is simple, taking only its type and the variable that the kernel acts on.

## 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

• eigen_postprocessor1The name of the postprocessor that provides the eigenvalue.

Default:1

C++ Type:PostprocessorName

Options:

Description:The name of the postprocessor that provides the eigenvalue.

• eigenTrueUse for eigenvalue problem (true) or source problem (false)

Default:True

C++ Type:bool

Options:

Description:Use for eigenvalue problem (true) or source problem (false)

• 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

### 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