i think that question has been brought up before, but i dont remember what the answer is.
i do know that the fins run a different direction than most cylinders - horizontal rather than vertical i guess you could say? they run side to side to catch air blowing from the fan rather than front to back to catch air moving past the moving bike.
so it wouldnt be exactly the same to just run it without the fan and let the movement of the bike do the work..