InitiateFacetElements

The InitiateFacetElements method initializes facet element data for an AbstractMesh_ object. Facet elements are essential for handling boundary conditions, inter-element flux computations, and discontinuous Galerkin methods.

Interface

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

Description

This method creates and populates the facetData array in the mesh object. Facet elements represent the interfaces between mesh elements (cells) and can be either internal facets (shared between two elements) or boundary facets (associated with a single element at the domain boundary).

The implementation:

1. Performs several validation checks:

   • Ensures the mesh has a valid dimension (not 0)
   • Checks if facet data is already initialized
   • Verifies element-to-element connectivity is available
   • Confirms boundary data is initialized

2. Allocates and initializes the facetData array with size equal to the total number of faces in the mesh (obj%tfaces)

3. Processes each active element in the mesh to extract facet data information

4. Uses the utility function GetFacetDataFromElemData to extract and populate facet data from element data

Implementation Details

The method requires:

• Element-to-element connectivity (InitiateElementToElements)
• Boundary data information (InitiateBoundaryData)

Both of these dependencies are automatically initialized if not already present.

The facet data extraction process:

• Iterates through all elements in the mesh
• Skips inactive elements
• Builds a comprehensive facet data structure that contains information about:
  • The element(s) sharing each facet
  • The local facet number within each element
  • Facet type (internal, boundary, domain boundary)
  • Facet connectivity

Usage

This method is typically called internally when facet information is needed:

TYPE(YourMeshType_) :: mesh
! Initialize mesh
CALL mesh%InitiateFacetElements()

Error Handling

The method includes error handling for these cases:

• Zero-dimensional meshes (returns without action)
• No faces found in the mesh (raises an error)

Notes

• Sets the isFacetDataInitiated flag to TRUE to prevent duplicate initialization
• Uses a masks array to track which facets have been processed
• Debug information is included when compiled with DEBUG_VER defined

This method is crucial for finite element methods that require integration over element boundaries or flux calculations across interfaces.