Automatic Scheme Selection for Toolkit Hex Meshing

2nd Symposium on Trends in Unstructured Mesh Generation, University of Colorado, Boulder, August 1999

MESHING
RESEARCH
CORNER

Sandia National Laboratories, P.O Box 5800, MS0441, Albuquerque, NM 87185-0441
[drwhite | tjtautg]@sandia.gov

Abstract
In the absence of a single hex meshing algorithm, the toolkit-based approach of meshing solid models has become mainstream. New volume meshing tools such as multi-sweep and submapping are being combined with traditional sweeping, mapping and primitive meshing to produce automated meshing. This paper presents another tool for further automation. It presents a method for automatically selecting schemes for meshing. The algorithm relies on geometric characteristics but is also heavily dependent on the types and variety of tools existing in the CUBIT toolkit.

Within automatic scheme selection, two algorithms in this paper will be detailed. First an algorithm for finding sweepable volumes, called 'automatic sweep detection', is described. This algorithm uses the surface schemes to form several loops of chained side surfaces. Through the existence of these loops, and proper traversal thereof, a volume can be determined sweepable. Additionally, the source and target surfaces for the sweep fall out automatically in this algorithm, further reducing user input.

Second, a method for grouping and ordering sweepable volumes for meshing is also presented. Often, a complicated assembly of parts is decomposed into several groups of non-manifold volumes. While each of the volumes can be easily meshed alone, meshing the collection often requires serial ordering. Sweep grouping finds the order, if one exists, for each collection of volumes to be meshed.

The automatic scheme selection algorithm in CUBIT has been used to reduce meshing time. In one example, a Neutron Generator Ion Target (Figure 1) at Sandia National Laboratories was decomposed initially from 67 initial parts to 243 volumes. Automatic scheme selection was used and returned 21 volumes that could not be meshed, reducing the users problem scope from 243 down to 21.

(Figure omitted)

Sandia National Laboratories is operated for the U.S. DOE under contract No. DE-AL04-94AL8500. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. DOE.