Learning Forum

[NvN]

Hello!

I am running a transient HEAT simulation using an imported heat source, a pulse in the form of the power absorbed file from lumerical FDTD. My simulation starts with everything at room temperature 293K with the boundaries of the simulation region held at 293K. However, as most of the particle I am looking at heats, there are locations of my simulation where the temperature drops well below RT to 279K. This is puzzling to me as I feel it should never drop below 293K.

[kghaffari]

Hi.
Thank you for reaching out. Good question. In the boundaries, positive sign indicates input power and negative sign indicates power dissipation. Therefore here, IÔÇÖd expect to see a negative value for P_temperature. As you have mentioned this is most likely leading to the unexpected temperature results.
This issue could be related to the mesh refinement. I would recommend decreasing the mesh size in your simulation and observing its impact on the results. You can do this through the global settings in the solver or by adding local mesh constraints. Please test and let me know if this helps.
Best regards

[NvN]

Dear kghaffari Thank you so much for your response, this makes good sense! If I have a bad mesh leading to rogue areas on the surface that drop below RT, and then it makes sense that the boundaries act as an input and inject power to the particle.
I ran a simulation with a 1nm mesh constraint and indeed there is significant improvement: now there are only drops by 3K and the power running through the boundary fully indicates power dissipation. I'm gonna keep trying to improve the mesh to completely resolve the issue.
Many thanks again Nika

[kghaffari]

Hi Nika Thank you for the update. Great to hear improving mesh refinement is effective here.
All the best Khash