github_edit: False

NonReflectingBC Syntax

The input file syntax for NonReflectingBC with the the [BCs] block provides syntax for creating the correct NonReflectingBC boundary condition objects for each spacial direction.

Example Usage

[BCs<<<{"href": "../index.html"}>>>]
  [./front]
    type = PresetDisplacement<<<{"description": "Prescribe the displacement on a given boundary in a given direction.", "href": "../../../source/bcs/PresetDisplacement.html"}>>>
    variable<<<{"description": "The name of the variable that this residual object operates on"}>>> = disp_x
    function<<<{"description": "Function describing the displacement."}>>> = x_vel
    boundary<<<{"description": "The list of boundary IDs from the mesh where this object applies"}>>> = front
    acceleration<<<{"description": "The acceleration variable."}>>> = accel_x
    velocity<<<{"description": "The velocity variable."}>>> = vel_x
    beta<<<{"description": "beta parameter for Newmark time integration."}>>> = 0.25
  [../]
  [./NonReflectingBC<<<{"href": "index.html"}>>>]
    [./back]
      displacements<<<{"description": "The vector of displacement variables. The size of this vector must be same as the number of dimensions."}>>> = 'disp_x disp_y disp_z'
      velocities<<<{"description": "The vector of velocity variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements."}>>> = 'vel_x vel_y vel_z'
      accelerations<<<{"description": "The vector of acceleration variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements."}>>> = 'accel_x accel_y accel_z'
      beta<<<{"description": "The beta parameter for Newmark time integration."}>>> = 0.25
      gamma<<<{"description": "The gamma parameter for Newmark time integration."}>>> = 0.5
      boundary<<<{"description": "The list of boundary IDs from the mesh where this boundary condition will be applied"}>>> = 'back'
      shear_wave_speed<<<{"description": "shear wave speed of the material."}>>> = 10.0
      p_wave_speed<<<{"description": "P-wave speed of the material."}>>> = 16.329931618554521
      density<<<{"description": "Density of the material."}>>> = 1.0
    [../]
  [../]
  [./Periodic<<<{"href": "../Periodic/index.html"}>>>]
    [./left_right]
      variable<<<{"description": "Variable for the periodic boundary condition"}>>> = 'disp_x disp_y disp_z'
      primary<<<{"description": "Boundary ID associated with the primary boundary."}>>> = 'left'
      secondary<<<{"description": "Boundary ID associated with the secondary boundary."}>>> = 'right'
      translation<<<{"description": "Vector that translates coordinates on the primary boundary to coordinates on the secondary boundary."}>>> = '1 0 0'
    [../]
    [./top_bottom]
      variable<<<{"description": "Variable for the periodic boundary condition"}>>> = 'disp_x disp_y disp_z'
      primary<<<{"description": "Boundary ID associated with the primary boundary."}>>> = 'bottom'
      secondary<<<{"description": "Boundary ID associated with the secondary boundary."}>>> = 'top'
      translation<<<{"description": "Vector that translates coordinates on the primary boundary to coordinates on the secondary boundary."}>>> = '0 1 0'
    [../]
  [../]
[]

Input Parameters

betaThe beta parameter for Newmark time integration.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The beta parameter for Newmark time integration.
boundaryThe list of boundary IDs from the mesh where this boundary condition will be applied
C++ Type:std::vector<BoundaryName>
Controllable:No
Description:The list of boundary IDs from the mesh where this boundary condition will be applied
densityDensity of the material.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Density of the material.
gammaThe gamma parameter for Newmark time integration.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The gamma parameter for Newmark time integration.
p_wave_speedP-wave speed of the material.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:P-wave speed of the material.
shear_wave_speedshear wave speed of the material.
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:shear wave speed of the material.

Required Parameters

accelerationsThe vector of acceleration variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The vector of acceleration variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements.
active__all__ If specified only the blocks named will be visited and made active
Default:__all__
C++ Type:std::vector<std::string>
Controllable:No
Description:If specified only the blocks named will be visited and made active
alpha0The alpha parameter for HHT time integration.
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The alpha parameter for HHT time integration.
displacementsThe vector of displacement variables. The size of this vector must be same as the number of dimensions.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The vector of displacement variables. The size of this vector must be same as the number of dimensions.
inactiveIf specified blocks matching these identifiers will be skipped.
C++ Type:std::vector<std::string>
Controllable:No
Description:If specified blocks matching these identifiers will be skipped.
velocitiesThe vector of velocity variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements.
C++ Type:std::vector<VariableName>
Unit:(no unit assumed)
Controllable:No
Description:The vector of velocity variables that are coupled to the displacement variables. The size of this vector must be same as that of displacements.

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.

Advanced Parameters

(test/tests/bcs/nonreflecting_bc/non_reflecting_bc_test.i)

#@requirement F6.2
# Test for non-reflecting boundary condition and application of seismic input

# This test consists of 20 brick elements stacked in the z direction.

# Back surface (z=0) is a non-reflecting boundary modeled using Lysmer damper.

# A sawtooth displacement of period 1 s is applied in the x direction to the front surface (z=1).

# The shear wave velocity of the soil material is 10 m/s. So the wave would take 0.1 second to reach from the front to back surface.

# The nodes on the sides are constrained to move together to periodic boundary.

# Result: The displacement at the back surface should almost be zero once the end of the wave has passed the back boundary (i.e., after 1.35 seconds in this case). This implies that most of the wave that that is incident on the boundary is absorbed by the boundary. Less than 1% of the incident wave is reflected back into the soil domain.

[Mesh]
  type = GeneratedMesh
  dim = 3
  nx = 1
  ny = 1
  nz = 20
  xmin = 0.0
  ymin = 0.0
  zmin = 0.0
  xmax = 1.0
  ymax = 1.0
  zmax = 1.0
[]


[Variables]
  [./disp_x]
  [../]
  [./disp_y]
  [../]
  [./disp_z]
  [../]
[]

[AuxVariables]
  [./vel_x]
  [../]
  [./accel_x]
  [../]
  [./vel_y]
  [../]
  [./accel_y]
  [../]
  [./vel_z]
  [../]
  [./accel_z]
  [../]
  [./layer]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[ICs]
  [./layer_ic]
    type = FunctionIC
    variable = layer
    function = layers
  [../]
[]

[Kernels]
  [./DynamicTensorMechanics]
    displacements = 'disp_x disp_y disp_z'
  [../]
  [./inertia_x]
    type = InertialForce
    variable = disp_x
    velocity = vel_x
    acceleration = accel_x
    beta = 0.25
    gamma = 0.5
  [../]
  [./inertia_y]
    type = InertialForce
    variable = disp_y
    velocity = vel_y
    acceleration = accel_y
    beta = 0.25
    gamma = 0.5
  [../]
  [./inertia_z]
    type = InertialForce
    variable = disp_z
    velocity = vel_z
    acceleration = accel_z
    beta = 0.25
    gamma = 0.5
  [../]
[]

[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]
  [./front]
    type = PresetDisplacement
    variable = disp_x
    function = x_vel
    boundary = front
    acceleration = accel_x
    velocity = vel_x
    beta = 0.25
  [../]
  [./NonReflectingBC]
    [./back]
      displacements = 'disp_x disp_y disp_z'
      velocities = 'vel_x vel_y vel_z'
      accelerations = 'accel_x accel_y accel_z'
      beta = 0.25
      gamma = 0.5
      boundary = 'back'
      shear_wave_speed = 10.0
      p_wave_speed = 16.329931618554521
      density = 1.0
    [../]
  [../]
  [./Periodic]
    [./left_right]
      variable = 'disp_x disp_y disp_z'
      primary = 'left'
      secondary = 'right'
      translation = '1 0 0'
    [../]
    [./top_bottom]
      variable = 'disp_x disp_y disp_z'
      primary = 'bottom'
      secondary = 'top'
      translation = '0 1 0'
    [../]
  [../]
[]

[Materials]
  [./Elasticity_tensor_1]
    type = ComputeIsotropicElasticityTensorSoil
    block = 0
    layer_variable = layer
    layer_ids = '10'
    shear_modulus = '1.0e+2'
    poissons_ratio = '0.2'
    density = '1.0'
  [../]

  [./strain_1]
    type = ComputeSmallStrain
    block = 0
    displacements = 'disp_x disp_y disp_z'
  [../]

  [./stress_1]
    type = ComputeLinearElasticStress
    block = 0
  [../]
[]

[Executioner]
  type = Transient
  solve_type = 'PJFNK'
  start_time = 0
  end_time = 3.0
  l_tol = 1e-6
  nl_rel_tol = 1e-6
  nl_abs_tol = 1e-6
  dt = 0.01
  timestep_tolerance = 1e-12
[]

[Functions]
  [./x_vel]
    type = PiecewiseLinear
    x = '0.0 0.25 0.5 0.75 1.0 1.25 2.0 3.0'
    y = '0.0 0.0  0.5 0.0 -0.5  0.0 0.0 0.0'
  [../]
  [./layers]
    type = ConstantFunction
    value = 10
  [../]
[]

[Postprocessors]
  [./_dt]
    type = TimestepSize
  [../]
  [./disp_1]
    type = NodalVariableValue
    nodeid = 83 # z=1(input)
    variable = disp_x
  [../]
  [./disp_2]
    type = NodalVariableValue
    nodeid = 77 # z=0.95
    variable = disp_x
  [../]
  [./disp_3]
    type = NodalVariableValue
    nodeid = 0 # z=0 (location of non-reflecting boundary)
    variable = disp_x
  [../]
[]

[Outputs]
  exodus = true
  csv = true
  print_linear_residuals = true
  perf_graph = true
[]

Example Usage
Input Parameters

Usage

Development

Demonstration

NonReflectingBC Syntax

Example Usage

Input Parameters

Required Parameters

Optional Parameters

Advanced Parameters