Formation of pyramid elements for hexahedra to tetrahedra transitions

New algorithms are proposed for the modification of a mixed hexahedra-tetra hedra element mesh to maintain compatibility by the insertion of pyramid el ements. Several methods for generation of the pyramids are presented involv ing local tetrahedral transformations and/or node insertion near the hex/te t interface. Local smoothing and topological operations improve the quality of the transition region. Results show superior performance of the resulti ng elements in a commercial finite-element code over nonconforming interfac e conditions. (C) 2001 Elsevier Science B.V. All rights reserved.