Density Scaling

Automatically scale the material density to achieve the desired time step size to satisfy CFL conditions.

Description

The material DensityScaling computes the extra element density required in every element to allow explicit dynamics solves to be solved with a time step prescribed by a user (see CriticalTimeStep). The addition of mass can alter the dynamics of the system, so usage of mass scaling is particularly recommended when the finite element mesh contains a handful of small finite elements or when system fundamental frequencies do not have a key influence on the simulation output metrics.

Example Input File

[Materials]
  [density_scaling]
    type = DensityScaling
    block = 0
    density = density
    desired_time_step = 0.06
    output_properties = density_scaling
    outputs = 'exodus'
    factor = 0.5
  []
[]

Input Parameters

densityName of Material Property or a constant real number defining the density of the material.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:Name of Material Property or a constant real number defining the density of the material.
desired_time_stepTime step to achieve.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Time step to achieve.

Required Parameters

blockThe list of blocks (ids or names) that this object will be applied
C++ Type:std::vector<SubdomainName>
Unit:(no unit assumed)
Controllable:No
Description:The list of blocks (ids or names) that this object will be applied
boundaryThe list of boundaries (ids or names) from the mesh where this object applies
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:The list of boundaries (ids or names) from the mesh where this object applies
computeTrueWhen false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:When false, MOOSE will not call compute methods on this material. The user must call computeProperties() after retrieving the MaterialBase via MaterialBasePropertyInterface::getMaterialBase(). Non-computed MaterialBases are not sorted for dependencies.
constant_onNONEWhen ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped
Default:NONE
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:NONE, ELEMENT, SUBDOMAIN
Controllable:No
Description:When ELEMENT, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps.When SUBDOMAIN, MOOSE will only call computeQpProperties() for the 0th quadrature point, and then copy that value to the other qps. Evaluations on element qps will be skipped
declare_suffixAn optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:An optional suffix parameter that can be appended to any declared properties. The suffix will be prepended with a '_' character.
factor1Factor to multiply to the critical time step. This factor is typically less than one to be on the conservative side due to two types of approximation: Time step lagging and the approximation of the critical time step formula.
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Factor to multiply to the critical time step. This factor is typically less than one to be on the conservative side due to two types of approximation: Time step lagging and the approximation of the critical time step formula.
prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:Yes
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
Unit:(no unit assumed)
Controllable:No
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
Unit:(no unit assumed)
Controllable:No
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
Unit:(no unit assumed)
Controllable:No
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

output_propertiesList of material properties, from this material, to output (outputs must also be defined to an output type)
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:List of material properties, from this material, to output (outputs must also be defined to an output type)
outputsnone Vector of output names where you would like to restrict the output of variables(s) associated with this object
Default:none
C++ Type:std::vector<OutputName>
Unit:(no unit assumed)
Controllable:No
Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object

Outputs Parameters

References

No citations exist within this document.

(moose/modules/solid_mechanics/test/tests/central_difference/consistent/3D/3d_consistent_explicit_mass_scaling.i)

# One element test to test the central difference time integrator in 3D.

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 1
  ny = 1
  nz = 2
  xmin = 0.0
  xmax = 1
  ymin = 0.0
  ymax = 1
  zmin = 0.0
  zmax = 2
[]

[Variables]
  [disp_x]
  []
  [disp_y]
  []
  [disp_z]
  []
[]

[AuxVariables]
  [vel_x]
  []
  [accel_x]
  []
  [vel_y]
  []
  [accel_y]
  []
  [vel_z]
  []
  [accel_z]
  []
[]

[AuxKernels]
  [accel_x]
    type = TestNewmarkTI
    variable = accel_x
    displacement = disp_x
    first = false
  []
  [vel_x]
    type = TestNewmarkTI
    variable = vel_x
    displacement = disp_x
  []
  [accel_y]
    type = TestNewmarkTI
    variable = accel_y
    displacement = disp_y
    first = false
  []
  [vel_y]
    type = TestNewmarkTI
    variable = vel_y
    displacement = disp_x
  []
  [accel_z]
    type = TestNewmarkTI
    variable = accel_z
    displacement = disp_z
    first = false
  []
  [vel_z]
    type = TestNewmarkTI
    variable = vel_z
    displacement = disp_z
  []
[]

[Kernels]
  [DynamicSolidMechanics]
    displacements = 'disp_x disp_y disp_z'
  []
  [inertia_x]
    type = InertialForce
    variable = disp_x
  []
  [inertia_y]
    type = InertialForce
    variable = disp_y
  []
  [inertia_z]
    type = InertialForce
    variable = disp_z
  []
[]

[BCs]
  [x_bot]
    type = FunctionDirichletBC
    variable = disp_x
    boundary = 'back'
    function = dispx
    preset = false
  []
  [y_bot]
    type = FunctionDirichletBC
    variable = disp_y
    boundary = 'back'
    function = dispy
    preset = false
  []
  [z_bot]
    type = FunctionDirichletBC
    variable = disp_z
    boundary = 'back'
    function = dispz
    preset = false
  []
  [Periodic]
    [x_dir]
      variable = 'disp_x disp_y disp_z'
      primary = 'left'
      secondary = 'right'
      translation = '1.0 0.0 0.0'
    []
    [y_dir]
      variable = 'disp_x disp_y disp_z'
      primary = 'bottom'
      secondary = 'top'
      translation = '0.0 1.0 0.0'
    []
  []
[]

[Functions]
  [dispx]
    type = PiecewiseLinear
    x = '0.0 1.0 2.0 3.0 4.0' # time
    y = '0.0 1.0 0.0 -1.0 0.0' # displacement
  []
  [dispy]
    type = ParsedFunction
    value = 0.1*t*t*sin(10*t)
  []
  [dispz]
    type = ParsedFunction
    value = 0.1*t*t*sin(20*t)
  []
[]

[Materials]
  [elasticity_tensor_block]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = 1e6
    poissons_ratio = 0.25
    block = 0
  []
  [strain_block]
    type = ComputeIncrementalStrain
    block = 0
    displacements = 'disp_x disp_y disp_z'
    implicit = false
  []
  [stress_block]
    type = ComputeFiniteStrainElasticStress
    block = 0
  []
  [density]
    type = GenericConstantMaterial
    block = 0
    prop_names = density
    prop_values = 1e4
  []
  [density_scaling]
    type = DensityScaling
    block = 0
    density = density
    desired_time_step = 0.06
    output_properties = density_scaling
    outputs = 'exodus'
    factor = 0.5
  []
[]

[Executioner]
  type = Transient
  start_time = -0.01
  end_time = 0.1
  dt = 0.005
  timestep_tolerance = 1e-6
  [TimeIntegrator]
    type = CentralDifference
    use_constant_mass = false
    solve_type = lumped
  []
  [TimeStepper]
    type = PostprocessorDT
    postprocessor = time_step
  []
[]

[Postprocessors]
  [accel_6x]
    type = NodalVariableValue
    nodeid = 6
    variable = accel_x
  []
  [time_step]
    type = CriticalTimeStep
    factor = 0.5
    density = density
    density_scaling = density_scaling
    execute_on = 'INITIAL TIMESTEP_END'
  []
[]

[Outputs]
  exodus = true
  csv = true
[]