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

To illustrate how such a saucer and a centrifugal impeller could be put together to generate a lift force via the Coanda effect, I have created a 3D CAD drawing using Autodesk Fusion 360 and I have displayed this drawing below in three different viewing perspectives.

The first drawing shows a cross-sectional view with the 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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Will a lift force be created by the Coanda effect if high velocity air flows under a half-toroid shaped saucer?

EDIT

I just want to point out that this question was migrated over from Aviation SE which is showing an older design that will most likely create very little or no lifting force. I have requested that this particular question be closed or deleted.

Please see a newer question that I asked on Engineering SE which shows a revised design that should create a lifting force: Will high velocity air directed underneath a half-toroid shaped Coanda saucer by a centrifugal impeller create a lifting force?

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    $\begingroup$ Physics is an experimental science. If you want to know how your device performs, build one and test it. Asking people for their opinions on a web site won't get you far. FWIW, if this generates any lift at all it won't be as efficient as existing methods. Frankly, i don't think it will work, but you could prove me wrong with some hard data. $\endgroup$
    – CatchAsCatchCan
    Commented May 25, 2021 at 0:27
  • $\begingroup$ @ CatchAsCatchCan, I am planning to built it on my 3D printer, but before I do so, I thought about first asking the Aviation community if my understanding of the Coanda effect was correct. I'm not really sure if an inverse Coanda effect will work or not. $\endgroup$
    – user33377
    Commented May 25, 2021 at 0:31
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    $\begingroup$ This doesn't seem to me to be an aviation question so much as one of physics. Have you considered asking on Physics? Check their help centre before you post. $\endgroup$
    – CatchAsCatchCan
    Commented May 25, 2021 at 2:42
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    $\begingroup$ That drawing should be updated to say "Desired Lift Force direction" .. $\endgroup$
    – Mr R
    Commented May 25, 2021 at 4:42
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    $\begingroup$ As an answer has suggested, googling "coanda propeller" or "coanda thruster" turns up lots of things which may give you further food for thought-- for example youtube.com/watch?v=WPUAq3QObp4 , youtube.com/watch?v=Irp_vnmUWZ4 $\endgroup$
    – quiet flyer
    Commented May 25, 2021 at 12:50

2 Answers 2

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It is important to realize any airborne device will go in the direction of the sum of all force vectors (including gravity).

We have our centrifugal impeller drawing air in from the bottom. The device will be pulled down.

The air flow out the sides will create low pressure, pulling the device down.

The device will have a better chance flying if it is inverted, but will still have efficiency issues.

But proof positive is to build a scale model and test it. Even in failure, things can be learned. Most importantly, even air has mass, and flow from the impeller will not likely bend in the manner illustrated.

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  • $\begingroup$ The way I see it happening is that if the high velocity air is pushed up into the toroid area of the saucer by ambient air pressure, the kinetic energy of the flowing air molecules will pushed up against the surface of the toroid area and this kinetic energy will be transferred into the saucer causing it to move in an upward direction. $\endgroup$
    – user33377
    Commented May 25, 2021 at 2:10
  • $\begingroup$ @ Robert DiGiovanni, one other thing... the centrifugal impeller could be turned around 180 degrees so that it would be pushed in an upward direction due to the low air pressure inside the impeller's air inlet. I'm thinking now that the motor could be placed below the impeller in order to rotate it. $\endgroup$
    – user33377
    Commented May 25, 2021 at 2:26
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    $\begingroup$ @user57467 good! Build it and try it! $\endgroup$
    – Robert DiGiovanni
    Commented May 25, 2021 at 8:54
  • $\begingroup$ @ Robert DiGiovanni, you are right in pointing out that this device will be pulled in a downward direction. I now understand why it will be pulled in a downward direction. $\endgroup$
    – user33377
    Commented Jun 1, 2021 at 15:42
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No. Lift will not be created.

The split toroid shape is not of any use. The airflow turning into the "donut" creates turbulence (and hence losses) and a downwards force since the airmass is accelerated upwards.

Further degrading any desired lift would be the fact that the air would mostly circulate out of and into the impeller. As mentioned in Robert's answer, the air should be pulled into the impeller from above, but it would still be by far less efficient than a simple propeller.

Google "coanda propeller" to find a plethora of evidence that coanda devices are not more efficient than simpler propeller arrangements.

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    $\begingroup$ I'm not trying to build something that will outperform a propeller-based aircraft because I agree that they are much more efficient than any Coanda-based aircraft. I'm going to make this on my 3D printer just out of scientific curiosity to find out if my understanding of the Coanda effect is correct. $\endgroup$
    – user33377
    Commented May 25, 2021 at 11:06
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    $\begingroup$ Kudos for curiosity! I bet a a simplier housing with only a downwards turning edge will produce more lift, I postulate the curvature upwards will yield no benefit. But I admit science is at it's best when it fails expectation. $\endgroup$
    – Jpe61
    Commented May 25, 2021 at 14:26
  • $\begingroup$ Oh sweet, did you just come here and revenge my downvote on your excavator answer by downvoting @Rob $\endgroup$
    – Jpe61
    Commented Nov 11, 2022 at 7:29