How is flow rate of air through a ceiling fan compared to its speeed of rotation?

The rating is in CFM (Cubic Feet per minute).

Donf is right with the CFM. However, it sounds like you are also asking about speed. Obviously the CFM increases as the fan goes faster. If you have a close fit fan, CFM is lower when blowing up due to air pressure. Bigger diameter fans= more CFM. Impossible to tell you how many CFM per speed since each fan brand speed is different.