Auto transmission system
 

Hi guys:
I am modeling whole car transmission system to see flow behaviour in various section of it (basically different gears and clutch pack which made of friction disks). Now the friction disks have many many grooves in it. It is impossible to model the friction disk with grooves, the CFD model without the friction disks is already more than 10 million cells. Now how can I model the friction disk space? I dont have any experimental data. Can I add all the surface area (through which the flow passes) of the grooves and make a groove with diameter which will give me the same surface area of the combined grooves? Any other idea?
Any body has any related paper?
Thanks.