No integrate around the disc, Juergen. Drag opposes to the forward flight. Integrate transversally an edge of the disc to the other and you will see that the load of the rotor disk is not the same as a circular wing.
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The Legacy of Martin Hollmann
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The full derivation is in naca 716 up to equation 25 roughly. The main point is that you have to stay consistent with Glauert's inflow calculationLast edited by kolibri282; 04022013, 02:52 PM.Cheers,
Juergen
..Il semble que la perfection soit atteinte..
....non quand il n'y a plus rien à ajouter,...
...mais quand il n'y a plus rien à retrancher...
 Antoine de SaintExupéry 
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Yes of course it is, but at that time only analytical expressions could be used. Wind tunnel measurements show that the induced velocity has a very marked longitudinal distribution. Mangler and Squire developed a Fourier series expansion that is the best analytical solution available (as far as I know to the day). They showed that the induced velocity component of the flow field can be treated as a small perturbation and for that case the flow field satisfies Laplace second order differential equation. Using this series Bramwell showed ("Helicopter Dynamics" p. 137ff) that induced power is 11% higher than for the constant case. If the lateral distribution is to be modeled as well you have to take recourse to numerical methods, e.g. the flat wake theory www.rotaryforum.com/forum/showthread.php?t=36560 or to a full fledged 3D CFD solution.
One must keep in mind though that very successful Helicopters like the Flettner Fl282 and the early Sikorsky types R4B and S51 have been designed using the assumption of a constant induced velocity.Last edited by kolibri282; 04032013, 01:01 AM.Cheers,
Juergen
..Il semble que la perfection soit atteinte..
....non quand il n'y a plus rien à ajouter,...
...mais quand il n'y a plus rien à retrancher...
 Antoine de SaintExupéry 
Comment

Everybody knew that the assumption of constant induced velocity would give a value that was too low. An increase of 15% seems to have been the accepted figure but nobody really cared since the error in fuselage drag was even larger and the error introduced by blade flexibility was as about the same magnitude. That is why the analytical solutions for two per rev flapping angles a2 and b2, which were availabel even in the early thirties, were also neglected.
The last equation on your page is by the way a simplified longitudinal distribution of induced velocity.Cheers,
Juergen
..Il semble que la perfection soit atteinte..
....non quand il n'y a plus rien à ajouter,...
...mais quand il n'y a plus rien à retrancher...
 Antoine de SaintExupéry 
Comment

Originally posted by kolibri282 View PostEverybody knew that the assumption of constant induced velocity would give a value that was too low. .
Also note that the longitudinal distribution (last equation) does not change the drag of the disk. Instead, the lateral distribution greatly influences the induced drag.Last edited by Jean Claude; 04032013, 05:03 AM.
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I only met the man once, at a conference in New York, knowing then nothing of his background or reputation. He was trying to sell the audience some theory he had cooked up that relied on achieving a vortex ring state in gyroplanes, and it seemed pretty bizarre to me. Ray Prouty was sitting near me, and when I asked him for his reaction, he was equally baffled by the whole thing.
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Also note that the longitudinal distribution (last equation) does not change the drag of the disk
http://www.rotaryforum.com/forum/showthread.php?t=37118Cheers,
Juergen
..Il semble que la perfection soit atteinte..
....non quand il n'y a plus rien à ajouter,...
...mais quand il n'y a plus rien à retrancher...
 Antoine de SaintExupéry 
Comment

There seems to be a personal account of Martin Hollmann building his autogyros. This is a bit surprising as the date on the page is /2017/03/07. Perhaps someone has an idea who the admin is who posted it?
http://www.buildagyrocopter.com/2017...rotorblades/
from here:
http://www.buildagyrocopter.com/
Cheers,
Juergen
..Il semble que la perfection soit atteinte..
....non quand il n'y a plus rien à ajouter,...
...mais quand il n'y a plus rien à retrancher...
 Antoine de SaintExupéry 
Comment

Build a gyro is a very strange site. Most of the posts are articles about dead people or dead designs. AND Air Command pilots NEVER got the girls.Tom Milton, PRA Director, Need a DAR, Seat tank, Prerotator, Rotor Brake, or Rotor Tach?
Have Airworthiness Certification questions? gyroplanes@aol.com or
Visit www.calumetair.com
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