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V is the freestream fluid velocity, typically the true airspeed of the aircraft or the water speed of the vessel

n is the rotational speed of the propeller in revolutions per unit of time

D is the propeller's diameter

Why in my aerodynamic book from aeronautics university write V/n in advance ratio formula is aerodynamic /"effective" pitch(I agree with that), but some members which are aerodynamics experts at this site said that this is geometric pitch(zero slip)?


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  • $\begingroup$ Uh...I've never said it's geometric pitch...In fact I've specifically told you it's not geometric pitch: aviation.stackexchange.com/questions/76922/… $\endgroup$ – JZYL Sep 16 '20 at 20:55
  • $\begingroup$ @JZYL Your first answer,before I get example with numbers was that is geometric.And you didnt confirm that is effective pitch...So agree with me and books that it is aerodynamic/"effective" pitch? $\endgroup$ – user52248 Sep 16 '20 at 21:01
  • $\begingroup$ No, you're misrepresenting my answer completely. My answer states: "The geometric pitch (p) is simply the distance that a point on the prop would move forward in one rotation, if it's gripping in a solid medium." That is not V! Air is not solid medium. And double no, that is not effective pitch either. $\endgroup$ – JZYL Sep 16 '20 at 21:15
  • $\begingroup$ @JZYL I never mention your description in post, I only refer to your comments to my question.If it is not geometric or effective pitch what is it?why would book write wrong? $\endgroup$ – user52248 Sep 16 '20 at 21:32
  • $\begingroup$ I suppose you can call it effective pitch. Seems like plenty of sources define it that way. I would ask that you remove part in your question about me saying it's geometric pitch. $\endgroup$ – JZYL Sep 16 '20 at 22:01

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