Unstructured_mesh_data
Contents
Data Structure: Unstructured_mesh_data |
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Unstructured mesh generation data structure |
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Unstructured_mesh_data NUM=ival where ival is the data structure number |
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Overview Main control data structure for unstructured mesh generation which defines: •The default target element size and upper and lower bound element sizes •The quality target for tetrahedral mesh generation •Target, minimum and maximum element sizes for specific lists of entities Target mesh sizes can be assigned to any geometry entity and are used to construct target mesh size distribution at the underlying geometry points. Mesh generation is then performed using the point-wise distribution. The point-wise value is evaluated by processing all the entities with specified values in the geometry hierarchy order; i.e. volume assignments are processed first, these are overwritten by surface assignments, which are over-written by line assignments, which are overwritten by point assignments. Notes •For unstructured mesh generation the Generation_algorithm on the Mesh_control_data structure must be set to 2 (Unstructured mesh generation).
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 | Default_element_size Default element size (Compulsory) |
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Default element size for the complete domain. This value will be assigned to all entities as a default mesh size which will then be overwritten by any specific mesh size assignments, either directly applied to the entity or defined using the Mesh_region data structures.
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| Volume_mesh_quality_target Target quality for 3-D tetrahedral meshing (Optional) |
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Target quality for 3-D tetrahedral meshing which can be used to attempt to improve the quality of tetrahedral elements using TetGEn Delaunay mesh generator. The quality measure is defined as the circum-radius/the shortest side length. For a tetrahedra with equal side lengths this has a value of ca. 0.612. The mesh quality target is used by TetGen to control the termination of the Delaunay mesh generation process, and once all the elements in the mesh satisfy this target, mesh generation is complete. The lower the target the higher the quality of the mesh but the longer the mesh generation will take. Also in some situations low quality targets may not be achievable resulting in failure of the mesh generation process. The default mesh quality target is 2.0 and the minimum allowable value is 1.05.
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| Element_sizes (or Element_size_bounds) Maximum and minimum element sizes (Optional) |
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Smoothing of target mesh density (size) is performed during unstructured mesh generation in order to ensure a smooth transition from fine to coarse mesh regions. Element size bounds allow specification of the maximum and minimum allowable element sizes in this smoothing process. If Element_sizes are not specified default values are automatically generated based on the Default_element_size. The data comprises: •Location 1 - Maximum element size •Location 2 - Minimum element size
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| Points List of Points (Optional) |
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List of points (vertices) that should be meshed using an unstructured mesh.
Notes •By default all points attached to higher level entities will be meshed if required. •Specification of points is only required if specific unstructured mesh generation data is to be assigned to these points.
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| Point_element_size Element size for Points (Optional, only if Points Specified) |
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Element size for each point (vertex).
Notes •Point_element_size should only be specified if Points is also specified. •Number of unstructured points must be identical for the Points and Point_element_size datasets.
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| Point_min_element_size Minimum element size for Points (Optional, only if Points Specified) |
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Lower bound element size for point (vertex).
Notes •Point_min_element_size should only be specified if Points is also specified. •Number of unstructured points must be identical for the Points and Point_min_element_size datasets.
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| Point_max_element_size Maximum element size for Points (Optional, only if Points Specified) |
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Upper bound element size for point (vertex).
Notes •Point_max_element_size should only be specified if Points is also specified. •Number of unstructured points must be identical for the Points and Point_max_element_size datasets.
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| Lines List of lines for unstructured mesh generation (Optional) |
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List of lines to be meshed using an unstructured mesh.
Notes •Specification of Lines is only required if specific unstructured mesh generation data is to be assigned to these lines.
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| Line_element_size Element size for lines (Optional, only if Lines Specified) |
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Element size for each line.
Notes •Line_element_size should only be specified if Lines is also specified. •Number of unstructured lines must be identical for the Lines and Line_element_size datasets.
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| Line_min_element_size Minimum element size for lines (Optional, only if Lines Specified) |
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Lower bound element size for lines.
Notes •Line_min_element_size should only be specified if Lines is also specified. •Number of unstructured lines must be identical for the Lines and Line_min_element_size datasets.
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| Line_max_element_size Minimum element size for lines (Optional, only if Lines Specified) |
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Upper bound element size for lines.
Notes •Line_max_element_size should only be specified if Lines is also specified. •Number of unstructured lines must be identical for the Lines and Line_max_element_size datasets.
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| Line_default_size Default element size for lines (Optional) |
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Default element size for lines.
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| Line_min_default_size Default minimum element size for lines (Optional) |
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Lower bound default element size for lines.
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| Line_max_default_size Default maximum element size for lines (Optional) |
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Upper bound default element size for lines.
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| Surfaces List of surfaces (Optional) |
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List of surfaces to be meshed using an unstructured mesh.
Notes •Specification of Surfaces is only required if specific unstructured mesh generation data is to be assigned to these surfaces.
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| Surface_element_size Element size for surfaces (Optional, only if Lines Specified) |
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Element size for surfaces.
Notes •Surface_element_size should only be specified if Surfaces is also specified. •Number of unstructured surfaces must be identical for the Surfaces and Surface_element_size datasets.
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| Surface_min_element_size Minimum element size for surfaces (Optional, only if Lines Specified) |
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Lower bound element size for surfaces.
Notes •Surface_min_element_size should only be specified if Surfaces is also specified. •Number of unstructured surfaces must be identical for the Surfaces and Surface_min_element_size datasets.
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| Surface_max_element_size Minimum element size for surfaces (Optional, only if Lines Specified) |
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Upper bound element size for surfaces.
Notes •Surface_max_element_size should only be specified if Surfaces is also specified. •Number of unstructured surfaces must be identical for the Surfaces and Surface_max_element_size datasets.
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| Surface_default_size Default element size for surfaces (Optional) |
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Default element size for surfaces.
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| Surface_min_default_size Default minimum element size for surfaces (Optional) |
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Lower bound default element size for surfaces.
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| Surface_max_default_size Default maximum element size for surfaces (Optional) |
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Upper bound default element size for surfaces.
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| Volumes List of volumes |
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List of volumes to be meshed using an unstructured mesh.
Notes •Specification of Volumes is only required if specific unstructured mesh generation data is to be assigned to these volumes.
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| Volume_element_size Element size for volumes |
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Element size for volumes.
Notes •Volume_element_size should only be specified if Volumes is also specified. •Number of unstructured volumes must be identical for the Volumes and Volume_element_size datasets.
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| Volume_min_element_size Minimum element size for volumes |
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Lower bound element size for volumes.
Notes •Volume_min_element_size should only be specified if Volumes is also specified. •Number of unstructured volumes must be identical for the Volumes and Volume_min_element_size datasets.
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| Volume_max_element_size Minimum element size for volumes |
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Upper bound element size for volumes.
Notes •Volume_max_element_size should only be specified if Volumes is also specified. •Number of unstructured volumes must be identical for the Volumes and Volume_max_element_size datasets.
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| Mesh_regions List of mesh region sets |
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List of mesh region sets with additional specific mesh generation data.
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| Curvature_sets List of mesh curvature sets |
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Specifies the list of mesh curvature sets to be used during initial mesh generation. Mesh curvature sets allow definition of mesh density based on the curvature of the lines and surfaces enabling refinement of the mesh in regions of high curvature.
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| Mesh_check_level Level of checking during mesh generation |
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The level of mesh checking during mesh generation of unstructured grids is generally set by default depending on the nature of the application; e.g. whether contact surfaces, which may result in overlapping geometry, are present. It may, however, be overridden by the user. Valid settings are: • "Simple" - Basic checking only • "Standard" - Standard checking applied to most applications • "High" - High level checking required if geometry is complex and may contain overlapping features (e.g. contact)
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| Fracture_tip_flag Flag indicating that the mesh generator should check for fracture/fault tip nodes |
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Checking for fracture/fault tip nodes if fractures or faults terminate at sharp points within surfaces (in 2-D) or within a single volume in 3-D. In this case additional steps are required to ensure mesh generation as slight overlap of elements may occur on the lines (2-D) or surfaces (3-D) adjacent to the fracture/fault surface. Consequently it is not generally required and is not used by default ( Fracture_tip_flag = 0). Valid settings are: • 0 - Do not check for fracture/fault tips • 1 - Check for fracture/fault tips
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| Line_angle_tolerance Facet angle tolerance for node insertion on unstructured lines |
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Facet angle tolerance for node insertion on unstructured lines. When defined if the angle between any two adjacent facets on a polyline background grid is greater than the specified angle a node will be inserted during unstructued mesh generation. If Line_angle_tolerance is not specified then the lines are assumed to be smooth.
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| Surface_smoothing_update Number of iterations for surface smoothing operation |
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Number of iterations for surface smoothing operation (default 10).
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| Mesh_smoothing_update Number of iterations for full mesh smoothing operation |
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Number of iterations for full mesh smoothing operation (default 0 - not used). Full mesh smoothing is only available in 2-D.
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| Orthotropic_mesh_sets List of Orthotropic mesh sets |
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List of Orthotropic mesh sets with additional specific mesh generation data.
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| Volume_hole_list List of volumes with holes |
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List of volumes with holes (one entry for each hole). A volume may occur more than once if it has multiple holes.
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| Hole_coordinates List of hole coordinates |
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List of coordinates of an arbirary location within each hole.
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