GeometricSearchData

  • Sometimes information needs to be exchanged between topologically-disconnected pieces of mesh which are in or near contact with each other.

  • Examples include: - Mechanical Contact - Gap Heat Conduction - Radiation - Constraints - Mesh Tying

  • The Geometric Search system allows an application to track evolving geometric relationships.

  • Currently, this entails two main capabilities: NearestNodeLocator and PenetrationLocator.

  • The PenetrationLocator capability defaults to a quick, mesh-topology-based location algorithm. Cases where a surface element may touch a node that is not one of its own nodes, such as Flex IGA meshes and adaptively-refined 3D meshes, should setSearchUsingPointLocator(true) to switch to a more thorough octree-based algorithm.

  • Most user interaction with GeometricSearchData is likely to be through objects which inherit from GeometricSearchInterface. Users can change the algorithm of PenetrationLocator by setting search_method=all_proximate_sides on such objects.

  • Both of the capabilities work in parallel and with both distributed and replicated meshes.

  • Locators can be requested using four different methods on the GeometricSearchData API: - getQuadraturePenetrationLocator - getPenetrationLocator - getQuadratureNearestNodeLocator - getNearestNodeLocator

  • The *Quadrature* based methods should be used within quadrature-point based objects like: - Materials e.g. the HeatConduction module's GapConductance object - IntegratedBCs e.g. the HeatConduction module's GapHeatTransfer object - Elemental AuxKernels e.g. the elemental versions of GapValueAux, NearestNodeDistanceAux, and PenetrationAux

  • The non-quadrature based methods should be used for nodal objects such as: - NodeFaceConstraints e.g. the Contact module's MechanicalContactConstraint object - Nodal AuxKernels e.g. the nodal versions of GapValueAux, NearestNodeDistanceAux, and PenetrationAux

  • geometric search objects like NearestNodeLocator and PenetrationLocator should hold to their geometric purpose and not call algebraic APIs like FEProblemBase::prepare which will query libMesh::DofObject information. This information may or may not have been initialized at the time that geometric search objects are being updated, so any query attempt may result in failed assertions or segmentation faults.