Pressure

Applies a pressure on a given boundary in a given direction

Description

The boundary condition, Pressure applies a force to a mesh boundary in the magnitude specified by the user. A component of the normal vector to the mesh surface (0, 1, or 2 corresponding to the $var element = document.getElementById("moose-equation-4b6c887c-3d24-4ffc-ac79-a3c6b76337d0");katex.render("\\hat{x}", element, {displayMode:false,throwOnError:false});$ , $var element = document.getElementById("moose-equation-694d2e88-811b-4697-a5a0-b826e119e0e1");katex.render("\\hat{y}", element, {displayMode:false,throwOnError:false});$ , and $var element = document.getElementById("moose-equation-caca48fc-4062-4a99-89e9-d4ee8861c518");katex.render("\\hat{z}", element, {displayMode:false,throwOnError:false});$ vector components) is used to determine the direction in which to apply the traction. The boundary condition is always applied to the displaced mesh.

The magnitude of the Pressure boundary condition can be specified as either a scalar (use the input parameter factor), a function parameter, or a Postprocessor name.

note:Can Be Created with the Pressure Action

A set of Pressure boundary conditions applied to multiple variables in multiple components can be defined with the PressureAction.

Example Input File Syntax

[./outerPressure]
  type = Pressure
  boundary = right
  variable = disp_r
  component = 0
  factor = 2
[../]

Input Parameters

boundaryThe list of boundary IDs from the mesh where the pressure will be applied
C++ Type:std::vector<BoundaryName>
Options:
Description:The list of boundary IDs from the mesh where the pressure will be applied

Required Parameters

active__all__ If specified only the blocks named will be visited and made active
Default:__all__
C++ Type:std::vector<std::string>
Options:
Description:If specified only the blocks named will be visited and made active
alpha0alpha parameter for HHT time integration
Default:0
C++ Type:double
Options:
Description:alpha parameter for HHT time integration
displacementsThe displacements appropriate for the simulation geometry and coordinate system
C++ Type:std::vector<VariableName>
Options:
Description:The displacements appropriate for the simulation geometry and coordinate system
factor1The factor to use in computing the pressure
Default:1
C++ Type:double
Options:
Description:The factor to use in computing the pressure
functionThe function that describes the pressure
C++ Type:FunctionName
Options:
Description:The function that describes the pressure
inactiveIf specified blocks matching these identifiers will be skipped.
C++ Type:std::vector<std::string>
Options:
Description:If specified blocks matching these identifiers will be skipped.
save_in_disp_xThe save_in variables for x displacement
C++ Type:std::vector<AuxVariableName>
Options:
Description:The save_in variables for x displacement
save_in_disp_yThe save_in variables for y displacement
C++ Type:std::vector<AuxVariableName>
Options:
Description:The save_in variables for y displacement
save_in_disp_zThe save_in variables for z displacement
C++ Type:std::vector<AuxVariableName>
Options:
Description:The save_in variables for z displacement
use_automatic_differentiationFalseFlag to use automatic differentiation (AD) objects when possible
Default:False
C++ Type:bool
Options:
Description:Flag to use automatic differentiation (AD) objects when possible

Optional Parameters

(moose/modules/tensor_mechanics/test/tests/1D_spherical/finiteStrain_1DSphere_hollow.i)

# This simulation models the mechanics solution for a hollow sphere under
# pressure, applied on the outer surfaces, using 1D spherical symmetry
# assumpitions.  The inner radius of the sphere, r = 4mm, is pinned to prevent
# rigid body movement of the sphere.
#
# From Bower (Applied Mechanics of Solids, 2008, available online at
# solidmechanics.org/text/Chapter4_1/Chapter4_1.htm), and applying the outer
# pressure and pinned displacement boundary conditions set in this simulation,
# the radial displacement is given by:
#
# u(r) = \frac{P(1 + v)(1 - 2v)b^3}{E(b^3(1 + v) + 2a^3(1-2v))} * (\frac{a^3}{r^2} - r)
#
# where P is the applied pressure, b is the outer radius, a is the inner radius,
# v is Poisson's ration, E is Young's Modulus, and r is the radial position.
#
# The radial stress is given by:
#
# S(r) = \frac{Pb^3}{b^3(1 + v) + 2a^3(1 - 2v)} * (\frac{2a^3}{r^3}(2v - 1) - (1 + v))
#
# The test assumes an inner radius of 4mm, and outer radius of 9 mm,
# zero displacement at r = 4mm, and an applied outer pressure of 2MPa.
# The radial stress is largest in the inner most element and, at an assumed
# mid element coordinate of 4.5mm, is equal to -2.545MPa.
[Mesh]
  type = GeneratedMesh
  dim = 1
  xmin = 4
  xmax = 9
  nx = 5
[]

[GlobalParams]
  displacements = 'disp_r'
[]

[Problem]
  coord_type = RSPHERICAL
[]

[Modules/TensorMechanics/Master]
  [./all]
    strain = FINITE
    add_variables = true
  [../]
[]

[AuxVariables]
  [./stress_rr]
    order = CONSTANT
    family = MONOMIAL
  [../]
[]

[Postprocessors]
  [./stress_rr]
    type = ElementAverageValue
    variable = stress_rr
  [../]
[]

[AuxKernels]
  [./stress_rr]
    type = RankTwoAux
    rank_two_tensor = stress
    index_i = 0
    index_j = 0
    variable = stress_rr
    execute_on = timestep_end
  [../]
[]

[BCs]
  [./innerDisp]
    type = DirichletBC
    boundary = left
    variable = disp_r
    value = 0.0
  [../]
  [./outerPressure]
    type = Pressure
    boundary = right
    variable = disp_r
    component = 0
    factor = 2
  [../]
[]

[Materials]
  [./Elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    poissons_ratio = 0.345
    youngs_modulus = 1e4
  [../]
  [./stress]
    type = ComputeFiniteStrainElasticStress
  [../]
[]

[Executioner]
  type = Transient
  solve_type = PJFNK
  line_search = none


# controls for linear iterations
  l_max_its = 100
  l_tol = 1e-8

# controls for nonlinear iterations
  nl_max_its = 15
  nl_rel_tol = 1e-10
  nl_abs_tol = 1e-5

# time control
  start_time = 0.0
  dt = 0.25
  dtmin = 0.0001
  end_time = 1.0
[]

[Outputs]
  exodus = true
[]

Description
Example Input File Syntax
Input Parameters