# 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 multipled 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


[AuxKernels]
[./x_disp]
type = FunctionAux
variable = x_disp
function = x_disp_func
[../]
[./y_disp]
type = FunctionAux
variable = y_disp
function = y_disp_func
[../]
[]
(moose/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

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

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

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

Default:True

C++ Type:bool

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

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

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

• 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