Learning Forum

[endo.s.ar]

Hello. I have a question of simulation for circle objects with FDTD.

I would like to simulate the reflection of a circle mirror structure, like the pasted photo.

How should I set the mesh?

For numerical calculation, it can be expected to have high reflectivity, but it is too low for FDTD.

I suspect that the mesh setting is not appropriate. The mesh is divided with rectangle shape.

I hope your advice!

[anna.wirth-singh]

Hi, thanks for your question. FDTD uses a rectilinear mesh, so meshing curved objects can be challenging. My recommendation is to first use an index monitor to view the mesh and qualitatively assess how well it represents your structure. If that seems ok, then a convergence test (see Convergence testing process for FDTD simulations – Ansys Optics) for the mesh accuracy can more quantitatively determine if the mesh is insufficient.

On the index monitor, ensure that the spatial interpolation setting is set to ‘NEAREST MESH CELL’ or ‘NONE’ to record the conformal mesh information. Then view the “index” result (not the simplified “index preview”) to see how the conformal mesh is being applied to your structure, for example:

See Refractive index monitor - Simulation object – Ansys Optics  for more information.

If the mesh seems insufficient (too coarse), then the best option is to refine the mesh near the curved area.  In the case of the pictured structure is the majority of the simulation region, so this will likely increase the simulation time.

To add a mesh override based on the structure, go to the geometry tab and select ‘based on a structure’ with the name of that object typed into the ‘structure’ box as shown in the screenshot below:

For more information, see Selecting the best mesh refinement option in the FDTD simulation object – Ansys Optics