Hi @JRangel, thanks for posting
Regarding the pressure drop, that’s completely expected in my evaluation due to your porous media assigments. Porous media will basically stablish a pressure difference between its ends.
Regarding the high velocity, I can only guess - but it seems related to the air being trapped in the racks and there being a power source there. Locally, the air will heat up quite a bit and buoyancy effects might be at fault for the higher velocity.
We can also consider that your simulation might not be converged locally, this is always a possibility.
As a final note, we do have this project as a template if that would help: Data Center - Master (Do Not Edit) by dlynch | SimScale
Cheers
Igor