Automatic Meshing

The PHOENICS Satellite module possesses an auto-meshing feature. By default it generates a grid from what it finds in the > OBJ lines in the Q1 file which has been presented to it, based upon a maximum cell size (as a fraction of the domain size), and a maximum change in cell size across region boundaries.

This default grid can, and often should, be modified by the user. The following picture shows how the above-shown grid has been further refined by the user's having increased the number of grid intervals per region:

The 'often should be' remark deserves attention; for the built-in auto-mesher responds to the existence of an object; but it knows nothing about its relative importance. Thus, in the above example, a large block on the left has some smaller ones by its side, for which the auto mesher has supplied fine-grid regions. Their physical presence may have no significant effect on the phenomena which the user is seeking to simulate; yet the finer grid may significantly increase the expense of performing that simulation.

Let the following image serve as a reminder: if the man and the stick appears in the Q1 as separate objects, the automesher devotes as many cells to the stick as to the man.

Users of the automesher are therefore advised always to inspect the grid which it has created, and then to remove unnecessary fine-grid regions.

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