ElementsToSimplicesConverter

Splits all non-simplex elements in a mesh into simplices.

An input mesh, as specified in the "input" parameter, will be modified to replace each non-simplex mesh element with a set of simplices connecting the same nodes. Each quad is split into 2 triangles, each pyramid into 2 tetrahedra, each prism into 3 tets, and each cube into 6 tets.

The input mesh must be "flat", not hierarchically refined.

The algorithm in 2D splits quads along their shortest interior diagonal, to try to improve element quality.

Currently the algorithm in 3D uses node ids to decide on splitting directions in a consistent way across face neighbors; this may change in the future.

In 3D, the geometry of any non-planar quadrilateral faces of cubes and/or prisms will not be exactly preserved, due to the change from bilinear or biquadratic mapping on quadrilaterals to linear or quadratic mapping on the triangles that replace them.

Input Parameters

inputInput mesh to convert to all-simplex mesh
C++ Type:MeshGeneratorName
Controllable:No
Description:Input mesh to convert to all-simplex mesh

Required Parameters

enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:No
Description:Set the enabled status of the MooseObject.
save_with_nameKeep the mesh from this mesh generator in memory with the name specified
C++ Type:std::string
Controllable:No
Description:Keep the mesh from this mesh generator in memory with the name specified

Advanced Parameters

nemesisFalseWhether or not to output the mesh file in the nemesisformat (only if output = true)
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not to output the mesh file in the nemesisformat (only if output = true)
outputFalseWhether or not to output the mesh file after generating the mesh
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not to output the mesh file after generating the mesh
show_infoFalseWhether or not to show mesh info after generating the mesh (bounding box, element types, sidesets, nodesets, subdomains, etc)
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not to show mesh info after generating the mesh (bounding box, element types, sidesets, nodesets, subdomains, etc)

Debugging Parameters

Input Files

(test/tests/meshgenerators/manifold_subdomain/cone.i)
(test/tests/meshgenerators/elements_to_simplices_converter/simple_convert.i)
(test/tests/meshgenerators/elements_to_simplices_converter/hex_prism_convert.i)
(modules/xfem/test/tests/solid_mechanics_basic/double_cantilever_crack.i)

(test/tests/meshgenerators/manifold_subdomain/cone.i)

expected = '2975'

!include check.i

[Mesh]
  [disk]
    type = ConcentricCircleMeshGenerator
    num_sectors = 6
    radii = '0.9'
    rings = '10'
    has_outer_square = false
    preserve_volumes = false
  []
  [cone]
    type = ParsedNodeTransformGenerator
    input = disk
    z_function = '0.9 - sqrt(x * x + y * y)'
  []
  [surface_quads]
    type = StitchMeshGenerator
    inputs = 'cone disk'
    stitch_boundaries_pairs = 'outer outer'
    clear_stitched_boundary_ids = true
  []

  [background]
    type = GeneratedMeshGenerator
    dim = 3
    nx = 25
    ny = 25
    nz = 25
    xmin = -1
    xmax = 1
    ymin = -1
    ymax = 1
    zmax = 1
  []

  [surface]
    type = ElementsToSimplicesConverter
    input = surface_quads
  []
  [tag]
    type = ManifoldSubdomainGenerator
    input = background
    manifold = surface
    block_id = 1
  []
  [remove]
    type = BlockDeletionGenerator
    input = tag
    block = '0'
  []
[]

(test/tests/meshgenerators/elements_to_simplices_converter/simple_convert.i)

[Mesh]
  [gmg]
    type = GeneratedMeshGenerator
    dim = 3
    nx = 1
    ny = 2
    nz = 2
  []
  [block_1]
    type = ParsedSubdomainMeshGenerator
    input = gmg
    combinatorial_geometry = 'z>0.5'
    block_id = 1
  []
  [convert]
    type = ElementsToSimplicesConverter
    input = block_1
  []

  # Simplices conversion currently depends on element id numbering
  allow_renumbering = false
[]

(test/tests/meshgenerators/elements_to_simplices_converter/hex_prism_convert.i)

[Mesh]
  [accg]
    type = FileMeshGenerator
    file = 'hex_prism_2d.e'
  []
  [extrude]
    type = AdvancedExtruderGenerator
    input = accg
    heights = '0.4 0.8 1.2'
    num_layers = '1 2 3'
    direction = '0 0 1'
    bottom_boundary = '200'
    top_boundary = '300'
    subdomain_swaps = '10 11 15 16;
                       10 12 15 17;
                       10 13 15 18'
  []
  [convert]
    type = ElementsToSimplicesConverter
    input = extrude
  []

  # Simplices conversion currently depends on element id numbering
  allow_renumbering = false
[]

(modules/xfem/test/tests/solid_mechanics_basic/double_cantilever_crack.i)

# 3D Double Cantiler beam example.
# Figure 9 in: Belytschko and Black (1999)
# https://doi.org/10.1002/(SICI)1097-0207(19990620)45:5<601::AID-NME598>3.0.CO;2-S

# to reproduce literature results the mesh must be refined, in addition to using smaller fracture domain integral radii and smaller crack growth increments
# search comments for "to reproduce literature use"

L = 11.8
H = 3.94
W = 4
poissons = 0.3
youngs = 3e7
a = 3.94
da = 0.3
dtheta = 5.71 # 1.43, 2.86, 5.71

[GlobalParams]
  displacements = 'disp_x disp_y disp_z'
  volumetric_locking_correction = true
[]

[XFEM]
  geometric_cut_userobjects = 'cut_mesh'
  qrule = volfrac
  output_cut_plane = true
[]

[Mesh]
  [cut_profile]
    type = PolyLineMeshGenerator
    loop = false
    points = '-0.01 0 -2.01
              ${a} 0 -2.01
              ${fparse a+da*cos(dtheta*pi/180)} ${fparse da*sin(dtheta*pi/180)} -2.01'
  []
  [cut_surfaace]
    type = AdvancedExtruderGenerator
    input = cut_profile
    direction = '0 0 1'
    heights = '4.02'
    num_layers = '3'
    biases = '1'
  []
  [tri]
    type = ElementsToSimplicesConverter
    input = cut_surfaace
    save_with_name = cut_mesh
  []

  [gen]
    type = GeneratedMeshGenerator
    dim = 3
    nx = 30 # to reproduce literature use 240
    ny = 11 # to reproduce literature use 81
    nz = 4 # to reproduce literature use 10
    xmin = 0
    xmax = ${L}
    ymin = '-${fparse H/2}'
    ymax = '${fparse H/2}'
    zmin = '-${fparse W/2}'
    zmax = '${fparse W/2}'
    elem_type = HEX8
  []
  [bottom_left_elem]
    type = ParsedGenerateSideset
    input = gen
    combinatorial_geometry = 'x < 0.21'
    normal = '0 -1 0'
    include_only_external_sides=true
    new_sideset_name = bottom_left_elem
  []
  [top_left_elem]
    type = ParsedGenerateSideset
    input = bottom_left_elem
    combinatorial_geometry = 'x < 0.21'
    normal = '0 1 0'
    include_only_external_sides=true
    new_sideset_name = top_left_elem
  []
  final_generator = 'top_left_elem'
[]

[Functions]
  [growth_func_v]
    type = ParsedFunction
    expression = 0.21 # to reproduce literature use 0.0125
  []
[]
[UserObjects]
  [cut_mesh]
    type = CrackMeshCut3DUserObject
    mesh_generator_name = 'cut_mesh'
    growth_dir_method = MAX_HOOP_STRESS
    size_control = 1
    n_step_growth = 1
    growth_rate = growth_func_v
  []
[]

[DomainIntegral]
  integrals = 'Jintegral InteractionIntegralKI InteractionIntegralKII'
  displacements = 'disp_x disp_y disp_z'
  crack_front_points_provider = cut_mesh
  crack_direction_method = CurvedCrackFront
  radius_inner = 0.42 # to reproduce literature use 0.1
  radius_outer = 1.0 # to reproduce literature use 0.3
  poissons_ratio = ${poissons}
  youngs_modulus = ${youngs}
  incremental = false
[]

[Physics/SolidMechanics/QuasiStatic]
  [all]
    strain = SMALL
    incremental = false
    generate_output = 'stress_xx stress_yy stress_zz vonmises_stress max_principal_stress'
    add_variables = true
  []
[]

[BCs]
  [right_x]
    type = DirichletBC
    boundary = 'right'
    variable = disp_x
    value = 0
  []
  [right_y]
    type = DirichletBC
    boundary = 'right'
    variable = disp_y
    value = 0
  []
  [right_z]
    type = DirichletBC
    boundary = 'right'
    variable = disp_z
    value = 0
  []
  [planar_z]
    type = DirichletBC
    boundary = 'front back'
    variable = disp_z
    value = 0
  []
  [bottom_left_elem_y]
    type = NeumannBC
    boundary = 'bottom_left_elem'
    variable = disp_y
    value = -1000
  []
  [top_left_elem_y]
    type = NeumannBC
    boundary = 'top_left_elem'
    variable = disp_y
    value = 1000
  []
[]

[Materials]
  [elasticity_tensor]
    type = ComputeIsotropicElasticityTensor
    youngs_modulus = ${youngs}
    poissons_ratio = ${poissons}
  []
  [stress]
    type = ComputeLinearElasticStress
  []
[]

[Executioner]
  type = Transient
  solve_type = 'NEWTON'
  petsc_options_iname = '-pc_type -pc_hypre_type -ksp_gmres_restart'
  petsc_options_value = 'hypre boomeramg 31'
  # petsc_options_iname = '-pc_type -pc_factor_mat_solver_package -pc_factor_shift_type -pc_factor_shift_amount'
  # petsc_options_value = ' lu       superlu_dist                 NONZERO               1e-20'
  line_search = 'none'
  nl_abs_tol = 1e-7
  dt = 1.0
  end_time = 8 # to reproduce literature use 100
  max_xfem_update = 1
[]

[Outputs]
  csv = true
  execute_on=final
[]

Input Parameters
Input Files