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

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

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
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
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
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.)
function1A function that describes the gravitational force
Default:1
C++ Type:FunctionName
Options:
Description:A function that describes the gravitational force
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.
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.)

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.
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
seed0The seed for the master random number generator
Default:0
C++ Type:unsigned int
Options:
Description:The seed for the master random number generator
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.

Advanced Parameters

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
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
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

Tagging Parameters

Input Files

modules/tensor_mechanics/test/tests/beam/dynamic/dyn_euler_small_added_mass_gravity.i

modules/tensor_mechanics/test/tests/beam/dynamic/dyn_euler_small_added_mass_gravity.i

# Test for small strain euler beam vibration in y direction
# Test uses NodalGravity instead of UserForcingFunctionNodalKernel to apply the
# force.

# An impulse load is applied at the end of a cantilever beam of length 4m.
# The beam is massless with a lumped mass at the end of the beam
# The properties of the cantilever beam are as follows:
# Young's modulus (E) = 1e4
# Shear modulus (G) = 4e7
# Shear coefficient (k) = 1.0
# Cross-section area (A) = 0.01
# Iy = 1e-4 = Iz
# Length (L)= 4 m
# mass = 0.01899772 at the cantilever end
# mass = 2.0 at the fixed end (just for file testing purposes does not alter result)

# For this beam, the dimensionless parameter alpha = kAGL^2/EI = 6.4e6
# Therefore, the beam behaves like a Euler-Bernoulli beam.

# The theoretical first frequency of this beam is:
# f1 = 1/(2 pi) * sqrt(3EI/(mL^3)) = 0.25

# This implies that the corresponding time period of this beam is 4s.

# The FEM solution for this beam with 10 element gives time periods of 4s with time step of 0.01s.
# A higher time step of 0.1 s is used in the test to reduce computational time.

# The time history from this analysis matches with that obtained from Abaqus.

# Values from the first few time steps are as follows:
# time   disp_y                vel_y                accel_y
# 0.0    0.0                   0.0                  0.0
# 0.1    0.0013076435060869    0.026152870121738    0.52305740243477
# 0.2    0.0051984378734383    0.051663017225289   -0.01285446036375
# 0.3    0.010269120909367     0.049750643493289   -0.02539301427625
# 0.4    0.015087433925158     0.046615616822532   -0.037307519138892
# 0.5    0.019534963888307     0.042334982440433   -0.048305168503101

[Mesh]
  type = GeneratedMesh
  xmin = 0.0
  xmax = 4.0
  nx = 10
  dim = 1
  displacements = 'disp_x disp_y disp_z'
[]

[Variables]
  [./disp_x]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_y]
    order = FIRST
    family = LAGRANGE
  [../]
  [./disp_z]
    order = FIRST
    family = LAGRANGE
  [../]
  [./rot_x]
    order = FIRST
    family = LAGRANGE
  [../]
  [./rot_y]
    order = FIRST
    family = LAGRANGE
  [../]
  [./rot_z]
    order = FIRST
    family = LAGRANGE
  [../]
[]

[AuxVariables]
  [./vel_x]
  order = FIRST
  family = LAGRANGE
  [../]
  [./vel_y]
  order = FIRST
  family = LAGRANGE
  [../]
  [./vel_z]
  order = FIRST
  family = LAGRANGE
  [../]
  [./accel_x]
  order = FIRST
  family = LAGRANGE
  [../]
  [./accel_y]
  order = FIRST
  family = LAGRANGE
  [../]
  [./accel_z]
  order = FIRST
  family = LAGRANGE
  [../]
[]

[AuxKernels]
  [./accel_x]
    type = NewmarkAccelAux
    variable = accel_x
    displacement = disp_x
    velocity = vel_x
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_x]
    type = NewmarkVelAux
    variable = vel_x
    acceleration = accel_x
    gamma = 0.5
    execute_on = timestep_end
  [../]
  [./accel_y]
    type = NewmarkAccelAux
    variable = accel_y
    displacement = disp_y
    velocity = vel_y
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_y]
    type = NewmarkVelAux
    variable = vel_y
    acceleration = accel_y
    gamma = 0.5
    execute_on = timestep_end
  [../]
  [./accel_z]
    type = NewmarkAccelAux
    variable = accel_z
    displacement = disp_z
    velocity = vel_z
    beta = 0.25
    execute_on = timestep_end
  [../]
  [./vel_z]
    type = NewmarkVelAux
    variable = vel_z
    acceleration = accel_z
    gamma = 0.5
    execute_on = timestep_end
  [../]
[]

[BCs]
  [./fixx1]
    type = DirichletBC
    variable = disp_x
    boundary = left
    value = 0.0
  [../]
  [./fixy1]
    type = DirichletBC
    variable = disp_y
    boundary = left
    value = 0.0
  [../]
  [./fixz1]
    type = DirichletBC
    variable = disp_z
    boundary = left
    value = 0.0
  [../]
  [./fixr1]
    type = DirichletBC
    variable = rot_x
    boundary = left
    value = 0.0
  [../]
  [./fixr2]
    type = DirichletBC
    variable = rot_y
    boundary = left
    value = 0.0
  [../]
  [./fixr3]
    type = DirichletBC
    variable = rot_z
    boundary = left
    value = 0.0
  [../]
[]

[NodalKernels]
  [./force_y2]
    type = NodalGravity
    variable = disp_y
    boundary = 'left right'
    gravity_value = 52.6378954948 # inverse of nodal mass at cantilever end
    function = force
  #  nodal_mass_file = nodal_mass.csv # commented out for testing purposes
  # mass = 0.01899772 # commented out for testing purposes
  [../]
  [./x_inertial]
    type = NodalTranslationalInertia
    variable = disp_x
    velocity = vel_x
    acceleration = accel_x
    boundary = right
    beta = 0.25
    gamma = 0.5
    mass = 0.01899772
  [../]
  [./y_inertial]
    type = NodalTranslationalInertia
    variable = disp_y
    velocity = vel_y
    acceleration = accel_y
    boundary = right
    beta = 0.25
    gamma = 0.5
    mass = 0.01899772
  [../]
  [./z_inertial]
    type = NodalTranslationalInertia
    variable = disp_z
    velocity = vel_z
    acceleration = accel_z
    boundary = right
    beta = 0.25
    gamma = 0.5
    mass = 0.01899772
  [../]
[]

[Functions]
  [./force]
    type = PiecewiseLinear
    x = '0.0 0.1 0.2 10.0'
    y = '0.0 1e-2  0.0  0.0'
  [../]
[]

[Preconditioning]
  [./smp]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient
  solve_type = NEWTON

  petsc_options_iname = '-ksp_type -pc_type'
  petsc_options_value = 'preonly   lu'

  dt = 0.1
  end_time = 5.0
  timestep_tolerance = 1e-6
[]

[Kernels]
  [./solid_disp_x]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 0
    variable = disp_x
  [../]
  [./solid_disp_y]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 1
    variable = disp_y
  [../]
  [./solid_disp_z]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 2
    variable = disp_z
  [../]
  [./solid_rot_x]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 3
    variable = rot_x
  [../]
  [./solid_rot_y]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 4
    variable = rot_y
  [../]
  [./solid_rot_z]
    type = StressDivergenceBeam
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    component = 5
    variable = rot_z
  [../]
[]

[Materials]
  [./elasticity]
    type = ComputeElasticityBeam
    youngs_modulus = 1.0e4
    poissons_ratio = -0.999875
    shear_coefficient = 1.0
    block = 0
  [../]
  [./strain]
    type = ComputeIncrementalBeamStrain
    block = '0'
    displacements = 'disp_x disp_y disp_z'
    rotations = 'rot_x rot_y rot_z'
    area = 0.01
    Ay = 0.0
    Az = 0.0
    Iy = 1.0e-4
    Iz = 1.0e-4
    y_orientation = '0.0 1.0 0.0'
  [../]
  [./stress]
    type = ComputeBeamResultants
    block = 0
  [../]
[]

[Postprocessors]
  [./disp_x]
    type = PointValue
    point = '4.0 0.0 0.0'
    variable = disp_x
  [../]
  [./disp_y]
    type = PointValue
    point = '4.0 0.0 0.0'
    variable = disp_y
  [../]
  [./vel_y]
    type = PointValue
    point = '4.0 0.0 0.0'
    variable = vel_y
  [../]
  [./accel_y]
    type = PointValue
    point = '4.0 0.0 0.0'
    variable = accel_y
  [../]
[]

[Outputs]
  file_base = dyn_euler_small_added_mass_out
  exodus = true
  csv = true
  perf_graph = true
[]

Input Parameters
Input Files

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Information and Tools

Nodal Gravity

Description

Input Parameters

Required Parameters

Optional Parameters

Advanced Parameters

Tagging Parameters

Input Files

Nodal Gravity

Description

/opt/civet/build_0/moose/modules/tensor_mechanics/test/tests/beam/dynamic/nodal_mass.csv

Input Parameters

Required Parameters

Optional Parameters

Advanced Parameters

Tagging Parameters

Input Files

modules/tensor_mechanics/test/tests/beam/dynamic/dyn_euler_small_added_mass_gravity.i