Partition Methods

The mesh is partitioned using a bisection or METIS algorithm. The selected algorithm is applied to the parent region, and then recursively applied to the subregions. For example, to divide the mesh into four partitions with a bisection method, the solver will bisect the entire (parent) region into two child regions, and then repeat the bisection for each of the child regions, yielding four partitions in total. To divide the mesh into three partitions with a bisection method, the solver will "bisect" the parent region to create two partitions—one approximately twice as large as the other—and then bisect the larger child region again to create three partitions in total. METIS uses graph partitioning techniques that generally provide more optimal partitions than the geometric methods.

The mesh can be partitioned using one of the two algorithms listed below. The most efficient choice is problem-dependent, so you can try either method to find the one that is best for your problem. See Ansys Fluent user documentation for more information.

• Metis uses the METIS software package for partitioning irregular graphs, developed by Karypis and Kumar at the University of Minnesota and the Army HPC Research Center. It uses a multilevel approach in which the vertices and edges on the fine graph are coalesced to form a coarse graph. The coarse graph is partitioned, and then uncoarsened back to the original graph. During coarsening and uncoarsening, algorithms are applied to permit high-quality partitions. METIS routines can handle partitioning with model-weighted multiple constraints: when automatically partitioning, solid cell zones are weighted with a default value of 0.1 relative to the fluid cell weighting; when manually partitioning, you can control weighting for cells, solid cell zones, VOF, DPM, and ISAT table lookup.
• Principal Axes bisects the region based on a coordinate frame aligned with the principal axes of the region. This reduces to Cartesian bisection when the principal axes are aligned with the Cartesian axes. The algorithm is also referred to as moment, inertial, or moment-of-inertia partitioning.