Re: Dummy Objects
Hi,
As I was told by Ansoft representative a long time ago when version 8 was out, the concept of dummy object was introduced to help the mesher by applying human knowledge and experience to come to the optimum mesh for the particular problem type with the less effort (passes) and waist of dense mesh points where it is not needed.
It is easier to explain this on a example - microstrip analysis. The large objects are initially evenlly meshed in the whole of their volume whole microstrip substrate. If left on its own , the program mesher will in later passes, based on the calculated energy stored in a single mesh tetrahedron, refine the mesh so that finely mesh areas correspond to large field/energy variation volumes. Finally, after some number of passes, the mesher will concentrate the dense points underneeth the microstrip track as this is the area of most rapid field variations, and the rest of the substrate will be much coarsely meshed.
However, although we don't know the solution to our problem and have to use EM sumulator to do calculations, we do know how the field of microstrip line looks like so we can be smart and place a dummy object, approximately 5 widths of the microstrip line in total symmetrically around the center of the microstrip line (2.5w to the left and 2.5w to the right) and dummy object should have the same height as microstrip substrate and use the same material. The object is much smaller than the whole microstrip substrate and will be initially meshed much finely that the rest of the substrate. So, by applying this method, the initial mesh will be much closer to the optimum one than in the "free running" mesh case.
However, HFSS mesher has been considerably improved since v8 and for v11 that is currently available, it is not needed to use dummy elements (as I was again told by the representative)
flyhigh