Automatic Hexahedral Sweep Mesh Generation of Open Volumes Nilanjan Mukherjee *1 , Bhanu Peddi 2 , Jean Cabello 3 & Michael Hancock 4 Meshing & Abstraction Group Digital Simulation Solutions Siemens PLM Software SIEMENS 2000 Eastman Dr., Milford, Ohio 45150 USA 1 {mukherjee.nilanjan@siemens.com} 2 {bhanu.peddi@siemens.com} 3 {jean.cabello@siemens.com} 4 {hancock.michael@siemens.com} * Author to whom all correspondence should be addressed Abstract: Open volumes with partial surface geometry are often encountered in the industry while modifying or morphing legacy meshes or while creating meshes in struc- tural recesses or void regions. The paper describes an algorithm for auto-generating hex- ahedral meshes on these open volumes without the need for laborious CAD repairs. Based on the available input, the open volumes are first topologically categorized into five classes. From the free edges and vertices of the open volume, a new, temporary, mesher-native and lightweight void-topology is first created. The void-topological net- work is supplemented by an underlying void-geometry which is also an abstract, light- weight, mesher-native discrete dataset. With the help of these void vertices and edges the open or void-volume is topologically and geometrically sealed. The source mesh is first morphed on the target if the latter is present. Transfinite meshing is done on the wall fac- es. A 2½D sweep meshing approach is used to complete the hex mesh. Thus, during the mesh generation process, facetted geometry is automatically created that can be handed over to the CAD engine. Keywords: open volume, hexahedral meshing, sweep, void topology, void geometry, transfinite. 1 Introduction Multiple industrial finite element analysis models experience “Open Volumes”. Some of these could be voids or structural recesses that are packed with non-structural material. Typical examples include void spaces between the content and its container filled with bubble material in drop-box analyses; epoxy or resin filled zones around fibrous material in micromechanical analyses, explosive filled spaces between missile parts, bone marrow spaces in bone cavity or interstitial fluid zones in bioengineering analyses etc. Remeshing legacy meshes and constructing new geometry from or around it has been a commonly used FE modeling procedure since the late 1990s. Such remeshing can encounter void spaces between two solid or shell meshes with partial geometry resulting in open vol- umes. Some typical examples are displayed in Figure 1. Traditional approach for gener- ating solid meshes in such void regions is to use CAD engines to create NURBS faces