HPC CFD analysis, Air flow inside rack (Beginner)

Hi,

I am modelling and simulating an HPC server room using Solidworks Flow simulation. The facility have 48 server racksa and 5 CRAC(Computer room AC) units with cold aisle containment model.   Now  I want to model the airflow inside the server rack. Each rack have been modelled as rectangular shaped boxes with several small rectangular cut through holes through which cold air can go inside the rack suk the heat generated by rack and go out from back side of rack. Cut through holes are assigned air inflow(2 m/s). Kindly see the attached images. Boundary conditions and inputs given are as below:

1. Cold air from CRAC: 6400 CFM

2. Rack volumetric hear generation: 21,000 W

3. Air flow through rack perforation: 2 m/s

But my model is showing too much time for completion: Around 3000 hrs. Now i am trying to minimize the complexity of my model for reducing the run time.

I am a beginner in this. Kindly suggest me any better model or any better way to model the air flow iside the rack.

SolidworksFlow Simulation