SignedDistanceToSurfaceMesh

SignedDistanceToSurfaceMesh is a Function that returns the signed distance to an arbitrary surface mesh. It extends UnsignedDistanceToSurfaceMesh by multiplying the unsigned nearest-boundary distance by a sign obtained from an in-out test user object (via in_out_test, a PointInPolyhedronCheckUO): the value is negative inside the surface and positive outside. As with the unsigned function, the gradient evaluates to the unit vector pointing from the boundary toward the query point.

Usage

Set the builder parameter to the SBMSurfaceMeshBuilder user object that stores the surface mesh, and in_out_test to a PointInPolyhedronCheckUO built from the same surface. Both user objects must be declared in the same execution block (for example inside [UserObjects]) and executed before any kernels request the function values.

Returns signed distance to a surface mesh using KDTree nearest neighbor search. The gradient returns the unit vector pointing from boundary to query point.

Input Parameters

builderSBMSurfaceMeshBuilder that provides KDTree, elem_id_map, and boundary elements.
C++ Type:UserObjectName
Controllable:No
Description:SBMSurfaceMeshBuilder that provides KDTree, elem_id_map, and boundary elements.
in_out_testThe name of the in-out test user object
C++ Type:UserObjectName
Controllable:No
Description:The name of the in-out test user object

Required 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.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:No
Description:Set the enabled status of the MooseObject.

Advanced Parameters

Input Files

(modules/shifted_boundary_method/test/tests/distance_calc/2D_signed_distance.i)

(modules/shifted_boundary_method/test/tests/distance_calc/2D_signed_distance.i)

nx = 16
# Asymmetric immersed geometry: a non-circular closed curve. A circle is maximally
# symmetric (every diameter is a symmetry axis), so an element centroid can sit
# exactly on a symmetry axis and become equidistant to two surface segments. That
# KDTree nearest-segment tie is broken only by floating-point round-off, which
# differs across platforms and flips the gradient direction. Deforming the boundary
# with a radial modulation removes all symmetry, so every centroid has a unique
# nearest segment and the in-out sign / gradient stay reproducible across platforms.
R = 1.3
cx = 2.03
cy = 1.97
# Control the boundary asymmetry (radial modulation amplitudes).
a = 0.18
b = 0.10
n_seg = 64
[Problem]
  solve = false
[]

[Mesh]
  [shift_boundary_mesh]
    type = ParsedCurveGenerator
    x_formula = '${cx} + ${R} * (1 + ${a} * cos(t) + ${b} * sin(2*t)) * cos(t)'
    y_formula = '${cy} + ${R} * (1 + ${a} * cos(t) + ${b} * sin(2*t)) * sin(t)'
    section_bounding_t_values = '0 ${fparse 2*pi}'
    nums_segments = '${n_seg}'
    is_closed_loop = true
    save_with_name = 'shift_boundary_mesh'
  []

  [gen]
    type = CartesianMeshGenerator
    dim = 2
    dx = '4'
    dy = '4'
    ix = '${nx}'
    iy = '${nx}'
    subdomain_id = '1'
  []

  add_subdomain_ids = 2 # outside block
  add_sideset_names = 'SBMinterface'
  final_generator = 'gen'
[]

[UserObjects]
  [TreeBuilder]
    type = SBMSurfaceMeshBuilder
    surface_mesh = shift_boundary_mesh
  []
  [signed_distance_to_surface]
    type = ShortestDistanceToSurface
    surfaces = 'sign_dist_square'
    signed_distance = true
  []
  [distance_to_surface]
    type = ShortestDistanceToSurface
    surfaces = 'dist_square'
  []
  [InOutTest]
    type = PointInPolyhedronCheckUO
    builder = TreeBuilder
    # A user-selected axis-aligned ray avoids the PCA/SVD direction ambiguity of
    # an isotropic shape (circle), which is not reproducible across platforms.
    point_containment_method = user_selected_ray
    ray_direction = '1 0 0'
  []
  [SignedFunctionTest]
    type = PointInSignedFunctionCheckUO
    function = level_set
  []
[]

[Functions]
  [level_set]
    # Const level set that is > 0, so if we union with this, it does not change any behavior
    # (IN/OUT/ON still remain).
    type = ConstantFunction
    value = 1
  []
  [dist_square]
    type = UnsignedDistanceToSurfaceMesh
    builder = TreeBuilder
  []
  [sign_dist_square]
    type = SignedDistanceToSurfaceMesh
    builder = TreeBuilder
    in_out_test = InOutTest
  []
[]

[Variables]
  [u]
    initial_condition = 1
    block = 1
  []
[]

[AuxVariables]
  [signed_distance]
    order = CONSTANT
    family = MONOMIAL
  []
  [unsigned_distance]
    order = CONSTANT
    family = MONOMIAL
  []
  # Vector field capturing the signed-distance gradient direction. Sampling the
  # gradient at every element centroid exercises points both inside and outside
  # the circle, so the gold pins down the outward-pointing direction on both sides.
  [signed_distance_grad]
    order = CONSTANT
    family = MONOMIAL_VEC
  []
[]

[AuxKernels]
  [signed_dist]
    type = ElementCentroidToSurfaceDistanceAux
    distance_to_surface = signed_distance_to_surface
    variable = signed_distance
    execute_on = 'INITIAL timestep_begin'
  []
  [unsigned_dist]
    type = ElementCentroidToSurfaceDistanceAux
    distance_to_surface = distance_to_surface
    variable = unsigned_distance
    execute_on = 'INITIAL timestep_begin'
  []
  [signed_dist_grad]
    type = FunctorElementalGradientAux
    functor = sign_dist_square
    variable = signed_distance_grad
    execute_on = 'INITIAL timestep_begin'
  []
[]

[Executioner]
  type = Steady
[]

[Outputs]
  exodus = true
[]

Usage
Input Parameters
Input Files