I would like to know if a lifting force will be created by the Coanda effect from high velocity air that is directed underneath a half-toroid shaped saucer by a centrifugal impeller.

I am seeking an answer to this question to make sure that I fully understand how the Coanda effect creates a lifting force so I do not waste time and materials building a prototype of it.

To illustrate how such a saucer and a centrifugal impeller could be put together to generate a lifting force via the Coanda effect, I created a 3D CAD drawing of it and I have displayed this drawing below in three different viewing perspectives.

The first drawing shows a cross-sectional view with its main components labeled, the second drawing shows a top side perspective view, and the third drawing shows a bottom side perspective view.

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I want to point out that this saucer is not a true half-toroid shape because one side of this toroid goes up at a 45 degree angle and the other side slopes downward in an arc. The reason for this 45 degree angle is to have the airflow go across a flat surface which should minimize the Coanda effect across this particular surface area of the saucer.

If I understand the Coanda effect correctly, the high velocity air exiting the centrifugal impeller should be pushed up into the half-toroid area of the saucer by ambient air pressure. Some of the kinetic energy of the high velocity air molecules pushing against the bottom surface of the saucer's toroid area should be transferred into the saucer which should cause the saucer to move in an upward direction.

There is a circular cutout in the center of the saucer to allow air to flow into the centrifugal impeller. (Inflowing air should rapidly rotate in order to enter into the rotating impeller creating an air vortex above the top surface of the saucer. This vortex should aid in lifting up the saucer, although this is secondary to the answer that I am seeking.)

Will high velocity air directed underneath a half-toroid shaped Coanda saucer by a centrifugal impeller create a lifting force?


I am thinking that the half-toroid area of the saucer should be larger in size so that the high velocity air will exert itself against a larger surface area resulting in a stronger lifting force. I also think that the air coming out of the centrifugal impeller should be as close as possible to the bottom surface of the saucer in order to keep any pockets of low static air pressure from forming there.

I have revised the original drawing to show this larger size and to show the repositioned centrifugal impeller.

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  • 1
    $\begingroup$ OMG it's an Area51 flying saucer! Anyway, the air has to go somewhere, and so long as the impeller output hits the outer wall, thus being directed downwards, momentum conservation demands the system will rise. My guess is this design will be inefficient because the impeller air will go horizontally, not along your desired blue curve, and thus not be directed directly vertically. $\endgroup$ May 26 at 13:12
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    $\begingroup$ Your saucer may fly, but not because of Coanda force. To take advantage of Coanda effect, the air should be directed along the outside curve of the saucer; clinging to the surface will make the flow head downward, thus transferring momentum in the downward direction. Similarly to a rocket, the saucer will then rise (but in practice, not by much) $\endgroup$ May 26 at 21:25
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    $\begingroup$ What you have is a 1 stage radial turbine. It has nothing almost nothing to do with the coanda effect. The machine as pictured probably won't have an adhered jet bending upwards. Instead, it will have a trapped vortex ring and the ducted flow will just shoot sideways. If it did adhere, it would produce a downward thrust due to Coanda, and the eventual upward thrust at the rim would not entirely offset this. You want a conventional bell nozzle like a rocket motor nozzle for this design. $\endgroup$
    – Phil Sweet
    May 26 at 21:50
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    $\begingroup$ Put the turbine wheel on the upper surface to build a Coanda saucer. $\endgroup$
    – Phil Sweet
    May 26 at 21:54
  • $\begingroup$ @PhilSweet, that's a good point you make about a trapped vortex ring, I had not thought about that. It makes me wonder now if this vortex ring will draw in air from below the saucer and this vortex ring will force that drawn in air up into the half toroid area increasing the dynamic air pressure against the bottom surface of the half-toroid area, which may increase the lifting force. I don't know if this would happen, I'm just theorizing about it. $\endgroup$
    – user57467
    May 26 at 22:35

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