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Yet another propeller question on this board.

I have done my research, both here & on google, but I cannot seem to find an answer.

Lets say I have a motor on wich I mount a propeller. This motor is static (not moving like on a flying airplane), so say its a small ventilator standing on my desk. What I want to know is the volume flow of air its generating at a certain motor rpm. This is what I do:

Prop pitch = 6"

Prop dia. = 9"

Motor rpm = 2000rpm

For 1 rotation, the prop moves the air 6"

For 2000 rotations, this means 12000". So the theoretical airflow speed would be 1000ft/min.

The disk area works out to 0,44 square foot.

So this would mean a volume flow of 440 CFM

Now my question; in how far is this value representative for the real flow? Does there exist a coefficient which takes this into account?

If someone could tell me a rough value this would also be good for giving me an idea..

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# From theoretical airflow speed of rotating propeller to a realistic value?

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