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31.5.1 Overview of Grid Partitioning

When you use the parallel solver in FLUENT, you need to partition or subdivide the grid into groups of cells that can be solved on separate processors (see Figure  31.5.1). You can either use the automatic partitioning algorithms when reading an unpartitioned grid into the parallel solver (recommended approach, described in Section  31.5.3), or perform the partitioning yourself in the serial solver or after reading a mesh into the parallel solver (as described in Section  31.5.4). In either case, the available partitioning methods are those described in Section  31.5.5. You can partition the grid before or after you set up the problem (by defining models, boundary conditions, etc.), although it is better to partition after the setup, due to some model dependencies (e.g., adaption on non-conformal interfaces, sliding-mesh and shell-conduction encapsulation).

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If your case file contains sliding meshes, or non-conformal interfaces on which you plan to perform adaption during the calculation, you will have to partition it in the serial solver. See Sections  31.5.3 and 31.5.4 for more information.

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If your case file contains a mesh generated by the GAMBIT Hex Core meshing scheme or the TGrid Mesh/Hexcore menu option (hexcore mesh), you must filter the mesh using the tpoly utility or TGrid prior to partitioning the grid. See Section  31.5.2 for more information.

Note that the relative distribution of cells among compute nodes will be maintained during grid adaption, except if non-conformal interfaces are present, so repartitioning after adaption is not required. See Section  31.5.7 for more information.

If you use the serial solver to set up the problem before partitioning, the machine on which you perform this task must have enough memory to read in the grid. If your grid is too large to be read into the serial solver, you can read the unpartitioned grid directly into the parallel solver (using the memory available in all the defined hosts) and have it automatically partitioned. In this case you will set up the problem after an initial partition has been made. You will then be able to manually repartition the case if necessary. See Sections  31.5.3 and 31.5.4 for additional details and limitations, and Section  31.5.6 for details about checking the partitions.

Figure 31.5.1: Partitioning the Grid
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