# Nodal Gravity

Computes the gravitational force for a given nodal mass.

# Description

This NodalKernel computes the gravitational force proportional to nodal mass in the coordinate direction corresponding to the assigned variable. A constant gravitational acceleration can be provided using gravity_value parameter and an acceleration varying in space and time can be provided using the function parameter. A constant mass for all the nodes in the given boundary can be provided using the mass parameter. Otherwise, a CSV file containing nodal positions and the corresponding nodal masses can also be provided using the nodal_mass_file parameter.

For example, the below csv file has two rows with 4 columns. The first three columns correspond to the nodal positions in the global coordinate system and the last column corresponds to the nodal mass. Each row contains position and mass information for one node.

0.0, 0.0, 0.0, 2.0
4.0, 0.0, 0.0, 0.01899772

(modules/tensor_mechanics/test/tests/beam/dynamic/nodal_mass.csv)

## Input Parameters

• variableThe name of the variable that this boundary condition applies to

C++ Type:NonlinearVariableName

Options:

Description:The name of the variable that this boundary condition applies to

### Required Parameters

• function1A function that describes the gravitational force

Default:1

C++ Type:FunctionName

Options:

Description:A function that describes the gravitational force

• save_inThe name of auxiliary variables to save this BC'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 BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• diag_save_inThe name of auxiliary variables to save this BC'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 BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• gravity_value0Acceleration due to gravity.

Default:0

C++ Type:double

Options:

Description:Acceleration due to gravity.

• massMass associated with the node

C++ Type:double

Options:

Description:Mass associated with the node

• nodal_mass_fileThe file containing the nodal positions and the corresponding nodal masses.

C++ Type:FileName

Options:

Description:The file containing the nodal positions and the corresponding nodal masses.

• alpha0Alpha parameter for mass dependent numerical damping induced by HHT time integration scheme

Default:0

C++ Type:double

Options:

Description:Alpha parameter for mass dependent numerical damping induced by HHT time integration scheme

• boundaryThe list of boundary IDs from the mesh where this boundary condition applies

C++ Type:std::vector

Options:

Description:The list of boundary IDs from the mesh where this boundary condition applies

• 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

• 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.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Options:

Description:Set the enabled status of the MooseObject.

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Options:

Description:The seed for the master random number generator

• 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

• 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.

• 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