[Bigfoot]

Hello,

I am an intermediate CFD user and a FloTHERM novice.

I have an enclosure with a board and several heat sources on it. These heat sources are cooled by 7 fans driving airflow out of the enclosure.

I have run this project with a few different meshes and I notice that the temperatures of the heat sources are fairly mesh independent (~3% variation) while the total flow rate through the box is highly mesh dependent (~100% variation).

Since the variation in flow rate does not cause a significant change in temperature of the heat sources, it leads me to believe that my model is capturing the physics near the heat sources on the board, but is not capturing the flow near the exit, i.e. near the fans correctly. I am also noticing something very curious - the operating points reported by FloTHERM for each fan are not on the fan curve! The static pressures being reported for the fans seem approximately right - but it makes no sense to me that FloTHERM is reporting incorrect flow rates for those fans given the static pressure it is computing. FYI - I am using an axial 3D 12 facet fan model to model the fans - not sure if that is the best choice for my situation.

I am wondering if any experts here can help me understand why this could be happening, and how to obtain confidence with the flow rate result.

Thanks,
Nikhil