How is the shape of the blades of an air fan determined? Trial and error, or is there a theory behind it? What are they trying to maximize, volume of air dislocated per rotation?

• I guess a follow up question is how do you measure the amount of air that is dislocated. – archgoon May 9 '11 at 19:24
• More on fans: physics.stackexchange.com/q/9030/2451 – Qmechanic May 9 '11 at 19:35
• +1 for using the Engineering tag. Got to support my kind :-) – John Alexiou May 10 '11 at 2:16
• 'Dyson' make a blade-less fan. No idea how it works though :P – qftme May 10 '11 at 8:03
• @qftme - there is a fan in base and then a series of angled holes in the ring shaped part that blow the air toward you. The clever part is that this high speed air drags more room air through the loop in the middle so gives you much more flow than the small hidden fan alone – Martin Beckett May 10 '11 at 15:34