Mesh Sizes Listed in HFSS Solution Profile

There are two different mesh sizes reported in the HFSS Solution Profile. This article shows how to interpret them.

For a solved model, the solution profile reports the number of tetrahedra mesh elements both for Adaptive Refine and for Simulation Setup / Matrix Assembly. The number of tetrahedra elements reported for Adaptive Refine corresponds to the total number of elements listed in the Mesh Statistics dialog. The number of tetrahedra elements reported for Simulation Setup / Matrix Assembly corresponds to the number of solved elements shown in the Convergence dialog table.

What is the difference between the reported mesh sizes?

These reported values can be different because the total number of elements shown in Mesh Statistics can include tetrahedra elements which are located inside electrically conducting objects. These objects are meshed by HFSS, but are not part of the solution matrix because HFSS does not solve for the field solution inside conductors (the electric field is zero inside good conductors). From a practical viewpoint, if the values are different it is best to view the model size as the number of solved elements since this correlates to the usage of computational resources.

Example #1: Microstrip patch antenna

In the coax-fed microstrip patch antenna model shown below, there are 44,518 tetrahedra elements listed in the solution profile for Adaptive Refine and also listed in Mesh Statistics. The model contains three electrically conducting objects named coax_pin, feed_pin, and port_cap. The "Solve Inside" setting is disabled for these objects by default because they are good conductors. Mesh Statistics shows that the coax_pin has 1,818 tetrahedra, the feed_pin has 658 tetrahedra, and the port_cap has 240 tetrahedra. Subtracting these tetrahedra, which are located inside conductors, from the total gives 41,802 tetrahedra which corresponds to the elements used in the solution matrix. The value of 41,802 elements is listed in the solution profile for Simulation Setup / Matrix Assembly and also shown in the Convergence table. 

Figure 1: Microstrip patch antenna model with 3D conducting objects

Figure 2: Solution profile reports different mesh sizes for Adaptive Refine and Simulation Setup / Matrix Assembly

Figure 3: Mesh statistics reports the mesh size for Adaptive Refine

Figure 4: Convergence table reports the mesh size for Solution Setup / Matrix Assembly

Example #2: Rectangular waveguide

When an HFSS model does not contain any three-dimensional (solid) electrical conductors having the "Solve Inside" setting disabled, the entire model domain will be meshed and the reported mesh sizes in the solution profile will be identical. In the example rectangular waveguide model shown below, there are 840 tetrahedra elements listed in Convergence table and also listed in Mesh Statistics. The model contains only the air-filled waveguide with boundary conditions used to model the conducting walls. 

Figure 5: Rectangular waveguide model with no 3D conducting objects

Figure 6: Mesh statistics reports the mesh size for Adaptive Refine

Figure 7: Convergence table reports the mesh size for Solution Setup / Matrix Assembly