I was thinking about propeller design just now and it came to mind that, theoretically, the air displaced by the propeller after every rotation might not be able to "flow back" into the area "served" by the propeller, resulting in a propeller surge, I guess you would call it.

Does this generally happen, is this accounted for in general or only in very detailed calculations or basically not at all? Does it have a name?

Edit: At high RPMs, of course.

  • $\begingroup$ I hope I'm understanding your question correctly. Propeller cavitation is the effect of airflow caused by a low pressure zone the propeller generates when it displaces the air. Here is a good video describing it's effect on submarine propellers: youtube.com/watch?v=ON_irzFAU9c $\endgroup$ – YAHsaves Sep 10 '18 at 0:09
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    $\begingroup$ I think what she is actually talking about is blade stall, since the prop is just a spinning wing. Mostly a problem for fixed pitch propellers where the static thrust is below the prop's potential because some of the blade is stalled, and thrust builds as the airplane accelerates and blade angle of attack goes down. I would think this is largely addressed by variable pitch/constant speed propellers which keep blade AOA closer to optimum most of the time. $\endgroup$ – John K Sep 10 '18 at 3:16
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    $\begingroup$ Perhaps you mean something like the 'vortex ring state', that sometimes appears in helicopter rotors, causing an abrupt loss of thrust. $\endgroup$ – xxavier Sep 10 '18 at 6:34
  • $\begingroup$ It was really just a blade stall actually, thinking about it, you're right @John K, though I guess the "disruption of airflow" is a kind of special case here! What I was wondering about is: Are blade stalls only accounted for in detailed foil-making for propellers or is it even in superficial calculations/designs a necessary or widespread variable? $\endgroup$ – Julie M. Sep 10 '18 at 21:05
  • $\begingroup$ @xxavier a vortex ring state requires a high descent rate in a helicopter (it's not the same as settling with power) something like 500 fpm or more. A propeller would have to be going backward. $\endgroup$ – John K Sep 11 '18 at 13:20

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