Heat Solver Simulation

Prateeksha

Hi,

1) I tried to follow following example for simulating my structure:

https://support.lumerical.com/hc/en-us/articles/360042833673-Thermally-tuned-waveguide-FDE-

But I am seeing constant temperature profile for my structure. What might be the reason?

2) Can we define Graphene as thermal conductor as well as heat source simultaneously? 

3) Is there any way to calculate thermal boundary conductance (TBC)

at the interface of two materials?

4) In the following example few layers of Graphene is 50 nm thick:

https://support.lumerical.com/hc/en-us/articles/360042273534-Transient-heat-flow-in-a-graphene-coated-glass

What thickness should be taken for single layer Graphene? Since heat solver is not having any option of 2D Graphene.

5) How does heat solver work for periodic structures? Since, I am simulating only unit cell.

Thanks

Prateeksha

kghaffari

Hi Prateeksha,

1-     So similar to the example, you are using a uniform heat source, is that correct? I would recommend confirming that this is being applied as expected and the value is large enough to make a considerable impact in the temperature profile. You can use the “boundaries” results in the solver to check the total power dissipated (through substrate, convection, etc.) which should match the expected input power set in your source.

2-     When applying uniform heat source to a volume, the volume itself will also be included in the simulation (unlike if thermal boundary condition is used); meaning the thermal conductance of the material should also be relevant.

3-     My understanding is that the temperature drop related to TBC is due to nanoscale molecular dynamics at the interface, which is not simulated in HEAT. If you already have an estimate of its impact, as a workaround you can define a buffer layer (between the two materials) with a thermal conductance such that the temperature drop will match your expectations.

4-     In the example the 50 nm thickness replicates the few-layer graphene (FLG) mentioned in the reference work. I would suggest testing the same approach by further reducing the thickness as needed. You might need to add local mesh constraints to ensure the smaller features are appropriately simulated.

5-     The simulation boundaries in HEAT assume symmetric boundary by default. So if your periodic structure is also symmetric then you can simply simulate a unit cell without any need of defining any special boundary conditions. For instance, this approach has been used in our Interleaved PN modulator example.

Kind regards,

Prateeksha

Hi,

Thank you for your reply!!

I tried to follow your instructions, but unable to figure out the issue. Could you please check my simulation files? I want to simulate a periodic grating with periodicity of 800 nm and check the thermal profile using Graphene heater.

In one case, I used 800 nm of simulation region (Reflector_unit_cell.ldev) and used power boundary condition to provide input power, then I am getting variation in temperature profile, but error in parametric variation.

In other case (Reflector_edited_bigger.ldev), I expanded the simulation domain larger than unit cell period, but then it's giving a job error. Here, I used uniform heat source.

Is there any difference in "power boundary condition" and "uniform heat source"?

Kindly check my simulation files attached.

New folder.zip

Looking forward to your reply!!

Thanks

Prateeksha

Prateeksha

Hi,

Have you checked my simulation files? If not, kindly check it. I really need your feedback.

Thanks in advance!!

Thanks

Prateeksha