Magnus effect - and Coanda effect
Thread Starter
Joined: Mar 2001
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From: Florida, USA
Magnus effect - and Coanda effect
I've been given some research to do - and I've tried, and tried...
With thanks to A.C. Kermode (Mechanics of Flight), I'm now aware of "Coanda" effect - water (or air) flowing over a cylindrical surface will follow the contour of the cylinder to the lowest point and then "fall off". Haven't a clue what we use that for in aviation, but I've read the stuff (briefly - need to go and study it properly).
What do we use it for?? I imagine that it will have something to do with airflow following the contour of the upper surface of the wing - but this goes against everything I was taught at basic PPL level about "separation point". I've obviously misunderstood something along the line...any help??
Now back to the original question...I cannot find any reference in any book (haven't tried an internet search...I'll do that next) about MAGNUS EFFECT.
What the h**l is it?? and what does it do??
With thanks to A.C. Kermode (Mechanics of Flight), I'm now aware of "Coanda" effect - water (or air) flowing over a cylindrical surface will follow the contour of the cylinder to the lowest point and then "fall off". Haven't a clue what we use that for in aviation, but I've read the stuff (briefly - need to go and study it properly).
What do we use it for?? I imagine that it will have something to do with airflow following the contour of the upper surface of the wing - but this goes against everything I was taught at basic PPL level about "separation point". I've obviously misunderstood something along the line...any help??
Now back to the original question...I cannot find any reference in any book (haven't tried an internet search...I'll do that next) about MAGNUS EFFECT.
What the h**l is it?? and what does it do??
Joined: Mar 2002
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From: Chicago
Ahhhhh.... it feels so good to have an effect named after yourself..... 
But seriously, the Magnus effect, or force, is simply put that a spinning object (like a tennis-ball or golf-ball) will create a "whirlpool" of rotating air around itself. On the side where the relative wind and the "whirlpool" of air is flowing in the same direction, the velocity of the air will increase, the pressure will drop, and we have lift. The opposite will happen on the side where the relative wind and the "whirlpool" of air is flowing in opposite directions.
But seriously, the Magnus effect, or force, is simply put that a spinning object (like a tennis-ball or golf-ball) will create a "whirlpool" of rotating air around itself. On the side where the relative wind and the "whirlpool" of air is flowing in the same direction, the velocity of the air will increase, the pressure will drop, and we have lift. The opposite will happen on the side where the relative wind and the "whirlpool" of air is flowing in opposite directions.
Joined: Mar 2002
Aviation Qualifications: CPL
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From: near an aeroplane
The Coanda effect is used very effectively on McDonnell Douglas's Helicopter models, and specifically the ones without a tailrotor. On these models the cylindrical boom has a lengthwise slit on one side through which air from an internal fan is blown out, downwards past the boom surface. This, coupled with the downwash from the rotor sets up a sidewards force created by the fact that the airflow past the boom on the side with the slit is higher, and therefore the pressure is lower (a bit like the interaction between the top and bottom wing surfaces).
What's good about this you might ask? Well, as the intensity of this force is controlled by the amount of downwash from the rotor, an increase in rotor speed will increase the side force and presto: there is no need for a rudder input as this automatically stabilizes the helicopter directionally! Of course there is still a need for rudder control and therefore there is a movable tailcone at the end which can direct a blast of air from the same internal fan to the right or left.
The Coanda effect, used here for getting the downwash to follow the tailboom contour, is therefore not totally useless in aviation!
As for how this applies to a wing: as a wing is not a cylindrical shape, the Coanda effect is not applicable here. So rest assured, your basic PPL aerodynamics are not affected by this in my view!
What's good about this you might ask? Well, as the intensity of this force is controlled by the amount of downwash from the rotor, an increase in rotor speed will increase the side force and presto: there is no need for a rudder input as this automatically stabilizes the helicopter directionally! Of course there is still a need for rudder control and therefore there is a movable tailcone at the end which can direct a blast of air from the same internal fan to the right or left.
The Coanda effect, used here for getting the downwash to follow the tailboom contour, is therefore not totally useless in aviation!
As for how this applies to a wing: as a wing is not a cylindrical shape, the Coanda effect is not applicable here. So rest assured, your basic PPL aerodynamics are not affected by this in my view!
Transparency International
Joined: Jul 2000
Aviation Qualifications: ATPL
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From: Denmark
Interesting guy this Coanda fellow http://www.deltawing.go.ro/history/coanda.htm
Joined: May 2000
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From: Seattle
I believe the Coanda effect was used in the ill-fated YC-14 and/or YC-15 US military cargo airplane prototypes. At least one of them had the engines mounted atop the wing, and used "upper surface blowing" over the flaps for STOL capability.
Joined: Feb 2002
Posts: 258
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From: Planet Earth
As for the Magnus-Effect: A brief search via Google offered the following:
http://www.geocities.com/k_achutarao/MAGNUS/magnus.html
http://www.mathpages.com/home/kmath258/kmath258.htm (quite scientific)
Have fun
http://www.geocities.com/k_achutarao/MAGNUS/magnus.html
http://www.mathpages.com/home/kmath258/kmath258.htm (quite scientific)
Have fun
Thread Starter
Joined: Mar 2001
Posts: 632
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From: Florida, USA
Well.....I did my search (on a quite fantastic page http://www.lerc.nasa.gov/WWW/K-12/airplane/short.html ) and found out, very quickly, about magnus effect (already understood coanda).
Question now is that these two topics where on a list of questions that were, supposedly, about the PA28.
Cannot think of anything that produces coanda on the a/c (other than, as said earlier, something to do with airflow above and below an aerofoil...but that screws up my separation point ideals).
Only thing I can think of which could produce magnus effect is the rotation of the wheels and tyres immediately after rotation - producing, I suppose, a very small downward "force" (opposing lift?? ????)
Anybody got any ideas??
Question now is that these two topics where on a list of questions that were, supposedly, about the PA28.
Cannot think of anything that produces coanda on the a/c (other than, as said earlier, something to do with airflow above and below an aerofoil...but that screws up my separation point ideals).
Only thing I can think of which could produce magnus effect is the rotation of the wheels and tyres immediately after rotation - producing, I suppose, a very small downward "force" (opposing lift?? ????)
Anybody got any ideas??
Joined: Dec 2000
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From: London, UK
GoneWest:
You may find these links:
http://www.monmouth.com/~jsd/how/htm...tml#sec-coanda
http://www.monmouth.com/~jsd/how/htm...l#sec-spinners
useful reading in relation to the Coanda / Magnus effects and their applicability to light aircraft. It's written by a physics PhD who presumably has a reasonable grasp of these things.
Unfortunately, if I understood correctly, his explanation is of how they are NOT relevant to the operation of light aircraft, rather than the other way around. Still, it's a very interesting read.
You may find these links:
http://www.monmouth.com/~jsd/how/htm...tml#sec-coanda
http://www.monmouth.com/~jsd/how/htm...l#sec-spinners
useful reading in relation to the Coanda / Magnus effects and their applicability to light aircraft. It's written by a physics PhD who presumably has a reasonable grasp of these things.
Unfortunately, if I understood correctly, his explanation is of how they are NOT relevant to the operation of light aircraft, rather than the other way around. Still, it's a very interesting read.
