GeometricSearchData

• Sometimes information needs to be exchanged between disconnected pieces of mesh.

• 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.

• Both of the capabilities work in parallel and with both Parallel- and Serial-Mesh.

• 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 MechanicalContactConstrant 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 segmentaton faults.