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 according to the meshing order, so that each subsequent part supplements the filled in mesh.
The left figure in the following example 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 one and the conductor with a meshing order of two. 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 one and the substrate's meshing order is two.
XF adheres to three rules when determining the meshing order. These rules also guide users in making 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 primary ordering method utilizes each part's priority level, all of which are equal at the default setting of 50 unless that value is changed. A higher or lower value gives an object more or less consideration, respectively, when meshed. For example, an object with a priority level of 49 is 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 is 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 a project's parts and displays it in the Parts List - Parts window. Users can view the meshing order by right-clicking on a part either in the Project Tree or the Geometry window, and selecting View Parts List. Users can also access this window by clicking View in the upper-left corner of XF and selecting Parts List (All Parts). Right-clicking on an assembly or one of its parts in the Project Tree opens a similar window listing only the parts contained in that assembly.
The parts list window displays the meshing order settings in the first through third columns, which include the meshing order, part's name, and priority level, respectively. XF determines this meshing order by adhering to the three rules previously described.
Change Meshing Order
Users cannot directly set the meshing order number per part, and adjusting the order by either editing the material properties or changing the order of parts within the project tree is impractical. The most efficient solution for changing the order is editing the meshing priority.
Users can change the meshing priority by right-clicking on a part either in the Project Tree or the Geometry window, and selecting Gridding/Meshing ❯ 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.