InitiateBoundaryData

Inheritence

This method is inherited from the AbstractMesh class.

InitiateBoundaryData

The InitiateBoundaryData method identifies and marks boundary elements and nodes within an AbstractMesh object. It establishes the necessary data structures to efficiently identify mesh boundaries and the elements adjacent to these boundaries.

note

This method construct the boundary-element data.

• It marks elements of mesh as DOMAIN_BOUNDARY_ELEMENT and INTERNAL_ELEMENT.
• In this case boundary elements are those which contains the boundary node.
• Boundary-node information is available by reading the mesh file, see mesh import method.
• It also forms obj%elementData(ii)%boundaryData.

note

This subroutine treats all boundary element as DOMAIN_BOUNDARY_ELEMENT because it does not have information of surrouding mesh. However, this is not correct. This is because, not all mesh boundary elements are domain boundary elements. For example, some mesh-boundary element may be interface element between two mesh regions. This information can be corrected by calling SetFacetElementType method from FEDomain_.

info

If we call InitiateBoundaryData, then we do not have to call SetFacetElementType because the former routine makes an internal call to the latter.

This method needs following information:

• ElementToElements
• refelem to construct the FacetElements

Purpose

This method analyzes the mesh to identify its boundaries and creates data structures that support:

• Application of boundary conditions
• Identification of domain interfaces
• Implementation of flux calculations at boundaries
• Visualization of boundary elements
• Mesh refinement at boundaries
• Domain decomposition algorithms
• Implementation of interface coupling techniques

INTERFACE
  MODULE SUBROUTINE obj_InitiateBoundaryData(obj)
    CLASS(AbstractMesh_), INTENT(INOUT) :: obj
  END SUBROUTINE obj_InitiateBoundaryData
END INTERFACE

• obj (INTENT(INOUT)) - The AbstractMesh_ object for which to initialize boundary data

Algorithm

1. If boundary data is already initialized (obj%isBoundaryDataInitiated is true), the method returns immediately
2. Ensures element-to-element connectivity has been established by calling obj%InitiateElementToElements() if necessary
3. Sets the initialization flag to true
4. For each element in the mesh:
   • Determines if the element is on the boundary by checking its connectivity
   • For boundary elements, identifies which faces lie on the boundary
   • Marks these faces as boundary faces
   • Updates the element's boundary data with the local face IDs
   • Updates node type information for nodes on boundary faces
5. Updates element type information to distinguish between:
   • Interior elements (fully inside the domain)
   • Boundary elements (containing at least one boundary face)
   • Domain boundary elements (on the external boundary)

Implementation Details

• Uses element-to-element connectivity to identify boundary faces (faces with no neighboring element)
• Stores boundary face information in the element data structure
• Updates node type information to identify boundary nodes
• Distinguishes between internal boundaries (between subdomains) and external boundaries
• Provides timing information when obj%showTime is enabled
• Includes debugging information when compiled with debug flags

Data Structures Modified

• obj%elementData(ii)%ptr%boundaryData - For boundary elements, stores the local face IDs that lie on boundaries
• obj%elementData(ii)%ptr%elementType - Updates element type to reflect boundary status
• obj%nodeData(ii)%ptr%nodeType - Updates node type to identify boundary nodes
• obj%isBoundaryDataInitiated - Flag indicating boundary data has been initialized

Element and Node Type Categorization

Elements can be categorized as:

• INTERNAL_ELEMENT - All faces connect to other elements
• BOUNDARY_ELEMENT - At least one face lies on a boundary
• DOMAIN_BOUNDARY_ELEMENT - Element on the external domain boundary

Nodes can be categorized as:

• INTERNAL_NODE - Not on any boundary
• BOUNDARY_NODE - On a boundary
• DOMAIN_BOUNDARY_NODE - On the external domain boundary

Performance Considerations

• Time complexity is O(n × f) where n is the number of elements and f is the average number of faces per element
• Memory usage scales with the number of boundary elements and faces
• Requires element-to-element connectivity information
• For large meshes, this operation can be computationally intensive

Usage Example

TYPE(FEMesh_) :: mesh
! ... Initialize mesh ...

! Build boundary data
CALL mesh%InitiateBoundaryData()

! Check if an element is on the boundary
IF (mesh%isBoundaryElement(elemNum)) THEN
  ! Get boundary faces for this element
  boundaryFaces = mesh%GetBoundaryElementData(elemNum)
END IF

Dependencies

This method depends on:

• Element-to-element connectivity (obj%InitiateElementToElements())
• Reference element information for identifying faces
• ElemData_ExpandBoundaryData for storing boundary face information
• NodeData_SetNodeType for marking boundary nodes

Notes

• This method is a prerequisite for many boundary-related operations
• The boundary identification depends on the correct establishment of element-to-element connectivity
• For multi-domain simulations, boundary elements may be further classified as domain boundaries or internal boundaries
• This method is automatically called by other methods that require boundary information