A standard for distinguishing two overlapping parts ensures they are correctly applied to the mesh, and avoids sending a questionable mesh to the calculation engine for simulation.
Each cell edge in the finite-difference time-domain (FDTD) grid requires that a single material be assigned to it. When parts with different materials overlap, it becomes difficult to determine which of those materials should be applied to the mesh. The meshing order is XF's mechanism for removing ambiguity. Parts are applied to the mesh sequentially beginning with the first one, as indicated by the meshing order. The remaining parts supplement the mesh, filling in around the initially included parts.
The left figure in the example below shows a CAD model of an antenna printed on a substrate. The mesh in the middle figure represents the substrate with a meshing order of 1 and the conductor with a meshing order of 2. This is problematic because the conductor was not included in the mesh and will therefore not be included in the simulation. The mesh in the figure on the right shows the issue is corrected when the conductor's meshing order is 1 and the substrate's meshing order is 2.
XF adheres to three rules for determining the meshing order, which also allow users to make any necessary adjustments.
- Select part with higher meshing priority.
- If priorities are equal, then select part with higher electric conductivity.
- If materials are equal, then select part that is closer to the top of the project tree.
XF's predominant ordering method utilizes each part's priority level, all of which are equal at the default setting of 50 unless the value is changed. Changing it to a higher or lower value gives the object more or less consideration, respectively, when meshed. For example, an object with a priority level of 49 will be applied to the mesh after a part with a priority level of 50. If two overlapping parts have equal priority levels, then the part with the higher conductivity will be applied to the mesh first. The meshing order of parts with both the same priority and conductivity is determined by the order in which they appear in the project tree.
View Meshing Order
XF maintains the meshing order for all the parts in the project and presents the list to the user in the parts list. The Meshing Order can be viewed by right-clicking on the part either in the Project Tree or the Geometry window, and selecting View Parts List. Right-clicking on an assembly or one of its parts within the Project Tree will access a Parts List containing only the parts in that assembly. The entire list can also be opened by clicking the View menu in the upper-left corner of XF, and selecting Parts List.
The meshing order settings are displayed in the parts list window, so the first through third columns show the meshing order, the part's name, and the priority level, respectively. The meshing order will match the order determined by the three rules above.
Change Meshing Order
Users cannot directly set the meshing order number per part, and adjusting the order by editing the material properties or changing the order of parts within the project tree is generally an impractical solution. Changing the order is best accomplished by editing the meshing priority.
Users can change the meshing priority by right-clicking on the part, clicking Gridding/Meshing, and selecting Meshing Order. The desired priority level can either be typed in using the Set Priority option, or adjusted to be higher or lower than that of an intersecting part by using the other available options.