I live close to a wind tunnel....Skeptical about it....Can freeflying in a tunnel hinder your ability to do it in a freefall??

[ASTKU 1]

Okay, So I live close to a wind tunnel and haven't gone. It's hard for me to spend my skydiving money on "floating" in a tunnel. Most people at my DZ have done some tunnel time but it seems like it wouldn't be as helpful as an actual skydive with your rig and all. I have jumped with people at about my jump number who have sitfly tunnel time and they are no better than me. I would think the wind tunnel would be great for belly work but be a little different if you were veritcal because of the fact you are missing your rig.....

Opinions and Experiences would be appreciated!!

THANKS

(BTW I have read some threads on the wind tunnel but haven't gotten all my questions answered)

[Jewels 0]

I think it's great that you're asking and that you're open to hearing what people have to say. Who knows what responses you'll get, but at least you're having the discussion.

Oh--and when they turn the wind speed up to free fly speeds, I wouldn't say it's much like "floating." You have to be able to fly it and stay in control.

TPM Sister #102

[Broke 0]

Just think about this. It is a lot easier to fall through the sky than it is to "Float" in a collum of air.

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[ASTKU 1]

Quote

Just think about this. It is a lot easier to fall through the sky than it is to "Float" in a collum of air.

Thanks for the reply.
But what I really want to know is, if you are vertical (head up or down) what role does your rig play. And does it make that much difference. Essentially you are "skydiving" without a rig and that rig will create resistence....

[Jewels 0]

Take sit flying as an example. Sometimes it's easy to tell when there is a skydiver in the wind tunnel because their body position for sit flying is different than the position you would be taught if you were learning to sit fly from the very beginning in the wind tunnel. It can take a bit of work to adjust their body position (which usually seems to involve leaning forward with arms out behind them--which would accommodate a rig) so that it works for tunnel flying. On the other hand, I've never heard my friends complain that they learned to sit in the tunnel but just couldn't make it translate to the sky. Perhaps someone with more credibility than my four jumps can chime in here.

TPM Sister #102

[hparrish 0]

Yes Freeflying in the Tunnel can help with Fine tuning the skills you already have.

But there are huge differences between tunnel flying and freeflying. The Rig is a big difference, but you can buy a rig wrap for the tunnel to address that issue. I think the other main difference is that in a tunnle you have to create lift where in skydiving you don't. But in the Tunnel you learn to fly on all axis, you are almost forced to do so, so that is a huge advantage. In the sky thats all most folks do is fall and deflect air.

I don't think that the folks who have only learned to freefly in the tunnel have an advantage over folks who have learned to freefly in the sky. Unless they have 100's or more hours of time in the tunnel. But even then they still have to learn exits, flying down to a group and stopping, chasing after folks, tracking, canopy piloting, etc......Its a good place to start but does not replace the skills learned in the sky.

But I do believe that the tunnel is EXCELLENT with Fine Tuning freeflying skills and making a sloppy freeflyer a more precise freeflyer.

I personally go to the tunnel as much as I can afford to do so. It can only make me a better freeflyer. But then I'm at a point in Freeflying where I'm looking to fine tune skills, not learn all the basics.

I think there is a place for both. And I don't think you'd be wasting you're money spending time in the Tunnel. Budget your time an money doing both and I think it will benefit you.

I will skydive during the Spring, Summer, and Fall and hit the tunnel hard during the Winter.

[pilotdave 0]

Quote

I think the other main difference is that in a tunnle you have to create lift where in skydiving you don't.

What do you mean by "create lift?" I assume you are saying that the wind speed in the tunnel is slower than your natural fallrate so you need to fly in a slower body position in the tunnel?

Dave

[hparrish 0]

Dave I know you already know the answer to this, but for others.........

Yes when you first learn in the tunnel the wind speed is turned down and slower so you have to learn to fly slower and create lift with your body. Atleast until you gain the skills to where they will crank up the wind speed.

So Learning to Freefly in the Tunnel is much different than learning in the sky. But thats not a bad thing. So many accomplished freeflyers seem to have a problem with having to start over.

I think they are just closed minded to a new way to learn how to fly better... I'm glad I took my time and really learned how to fly differently through the tunnel progression.

I seem to remember hearing about s certain Freelyer with 17,000 Freely jumps breaking both arms in the tunnel, trying to fly headdown and hitting the glass. That was my reality check, about being open minded.

[Jewels 0]

Quote

I seem to remember hearing about s certain Freelyer with 17,000 Freely jumps breaking both arms in the tunnel, trying to fly headdown and hitting the glass. That was my reality check, about being open minded.

So . . . you're saying YES, that freeflying in a tunnel can hinder your ability to do it in freefall if you break both your arms doing it?

TPM Sister #102

[rehmwa 2]

Quote

Quote

I seem to remember hearing about s certain Freelyer with 17,000 Freely jumps breaking both arms in the tunnel, trying to fly headdown and hitting the glass. That was my reality check, about being open minded.

So . . . you're saying YES, that freeflying in a tunnel can hinder your ability to do it in freefall if you break both your arms doing it?

we shouldn't be using arms that much anyway

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[Jewels 0]

Good point. Throw on a couple of casts and fly your legs!

Hey, you're a skydiver. . . . What do YOU think about the rig and how much difference there is in freeflying in the tunnel as opposed to the sky because of the rig factor?

TPM Sister #102

[CMiller 1]

Quote

Thanks for the reply.
But what I really want to know is, if you are vertical (head up or down) what role does your rig play. And does it make that much difference. Essentially you are "skydiving" without a rig and that rig will create resistence....

I've only tried backflying in the tunnel, but I can say that it's noticeably different without the rig.

[pinkfairy 0]

The top teams such as Skywalkers and Babylon are flying in the tunnel to improve their skills, so of course it helps.

But just going in there and trying for yourself will not be very helpful, you should get a good coach.

I'm a belly flyer, and what tunnel time does for us, is make us able to stay in one place and not float around the whole sky. We also get faster and more precise in our movements, as we get more practice. Those abilities must be useful in freeflying too, after all you are doing relative work just like us.

But by all means, if you'd rather spend your money on skydiving, then do it.

Some tunnels have dummy rigs that you can borrow. Some tunnels also charge extra for flying that requires extra powerful airstream, such as prolonged head down.

Relax, you can die if you mess up, but it will probably not be by bullet.

I'm a BIG, TOUGH BIGWAY FORMATION SKYDIVER! What are you?

[mdrejhon 8]

To make tunnel REALLY count in the sky, I think you need plenty of tunnel time.

I think that jumping with freeflyers who only has 15 minutes tunnel time, or even 60 minutes of tunnel time won't really show statistically. But people with as much tunnel time as freefall time (i.e. 300 jump person with 4 hours freefly tunnel time in the same time period, will probably perform better than a 500 jump freeflier of similiar time period), they tend to start to stand out statistically... They are the people who really put the money where their time counts. The professional teams, including those mentioned above, are an example.

Basically, you can do 200+ skydives of freefly tunnel time (say, 4 hours) in less than one month -- and you only need to spend two weekends at the tunnel to get this much flight time, assuming your body is adapted to do 2 hours of tunnel time per weekend. (You need to ease in. 15 minutes can get you very sore on the first time, until you're tuned to it -- then 2 hours in eight different 15-minute sessions in one day, with 1 hour rest breaks in between, is no problem. That's like 120 skydives in one day).

Tunnel is an excellent time management tool for some - if your time is more valuable than others -- and can't go to the dropzone every weekend. 300 jump bellyfliers with 8 hour tunnel time, can get more skilled in the same time period (while spending less time away from home and work) as 600 jump bellyfliers with no tunnel time. Tunnel can be used in the winter when dropzones are closed, a good thing for Northerners. Also, tunnel may be expensive, which means many won't go to the necessary "critical mass" of tunnel time necessary.

Also, the right instructor is very important. That's why using tunnel to train for bigways, it's recommended to use a RW/bigway experienced instructor (who happens to also be a tunnel instructor) to teach you the correct skills that are the biggest help in bigways. Perris Fury at Skydive Perris is one example, and helped me into the 100-way club with the help of wind tunnels, among other tunnel time elsewhere (Team Evolution at Skyventure New Hampshire) So for freeflying, the right instructor is probably important -- so they can help you learn how it translates to the sky as well. Tunnels won't teach you everything (exits, diving, tracking, canopy, etc) but properly used, can be a force-multiplier in approximately halving or thirding the number of jumps required to meet a specific level in a particular discipline.

Tunnel time is a long term investment. 15 minutes won't turn someone into anyone resembling a skygod (of the good kind) in a particular discipline -- but hours and hours of tunnel time COMBINED with lots of skydives might.

Look at the best teams -- Airspeed, Fury -- look at most of the only World Team Members that has under 1000 jumps -- look at the 150+ jump russian that managed to qualify his way through multiple bigways all the way to a 100-way in Perris while I was there. Even some of the better freefly 3-way and 4-way teams. All of these people have HOURS and HOURS of tunnel time in common.

[Chrisky 0]

I've only recently started freeflying in the tunnel and the rig factor is negligeable (Have 8 hrs total now and just had headdown liftoff). While it is true that you can use your back and shoulders to greater effect in the tunnel (at least sitflying), you still can use this move when you're in the sky with a rig on. It takes a couple of jumps to transfer the tunnel moves to the sky, but in general the felt understanding of the airflow will increase significantly. The bigger difference rather than the rig I feel is the density of the air. The tunnels compress the air in the chamber for the Bernoulli effect, thus the air feels much harder and denser in the tunnel. It will feel softer outside.

My take on your choices in learning to freefly in the sky or in the tunnel: tunnel. Will get you there from scratch much faster than in the sky, at far less cost. Obviously, flying in the tunnel doesn't have the beauty of outside flying. But, if you're just starting out, you wont have to unlearn bad habits you trained in learning it in the sky. In the sky you cant tell whether you are moving 20 feet, in the tunnel you'll see it immediately. Invaluable training.

For me, the tunnel will never replace skydiving, cause outside is just more beautiful and canopy rides rock, swooping rocks.
But the precision and control you get on your moves in the tunnel have their own appeal.

ETA: Of course, coaching and serious commitment is what counts. To start out, I recommend at least 90-120 minutes with coaching to get you anywhere you can see results. Shitload of money, yes, but well spent and much cheaper than equivalent time in skydives, especially considering coach jumps.

The mind is like a parachute - it only works once it's open.
From the edge you just see more.
... Not every Swooper hooks & not every Hooker swoops ...

[rehmwa 2]

Quote

Good point. Throw on a couple of casts and fly your legs!

Hey, you're a skydiver. . . . What do YOU think about the rig and how much difference there is in freeflying in the tunnel as opposed to the sky because of the rig factor?

The rig is a huge effect for 4-way, IMO (seems verts and momentum, etc are all affected). It's easier to do everything in the tunnel with the references and not having 20 pounds and a 4 inch thick wind baffle on my back.

It's even more an impact for sit flying, IMO. But, conversely, it seems 'easier' in the air than the tunnel. Caviat, I'm new in the tunnel sitflying and they haven't turned it up, so I do have to work to get up and flying off the net - as pointed out above. But that's a big help really, verts and carving and other moves have to be really defined since I'm also focusing on keeping my feet off the net at the same time......

I'm not good enough to headdown in the tunnel yet, so I have no point for comparison.


BUT - the things, basics, I've learned in the tunnel for belly and for sit all seem to apply significantly in the air anyway.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[jerm 0]

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Quote

I think the other main difference is that in a tunnle you have to create lift where in skydiving you don't.

What do you mean by "create lift?" I assume you are saying that the wind speed in the tunnel is slower than your natural fallrate so you need to fly in a slower body position in the tunnel?

this is an annoying misnomer that the tunnel world seems to have adopted, mean to increase drag, or more specifically, "increasing drag to lift you up"

Does anyone else grit their teeth when they hear this used? I know it's just tunnel jargon, but damnit, if you're using "flying" and "lift" in the same context there should be come continuity.

I know in relative terms it works, but people still think opening a parachute pops you up because of similar issues of relative speed/viewpoints, too.

Landing without injury is not necessarily evidence that you didn't fuck up... it just means you got away with it this time

[selwyn 0]

i use the annoying polyonmer thing -- because when your flying in a tunnel or relative to another flyer in the sky -- increasing your surface area of your wings (limbs) creates visual lift .

but as we are being pedantic

Lift (force)
From Wikipedia, the free encyclopedia
Jump to: navigation, search
In the context of a fluid flow relative to a body, the lift force is the component of the aerodynamic force that is perpendicular to the flow direction. It contrasts with the drag force, which is the parallel component of the aerodynamic force.

Lift is commonly associated with the wing of an aircraft, although lift is also generated by rotors on helicopters, sails and keels on sailboats, hydrofoils, wing on auto racing cars, and wind turbines. While common meanings of the word "lift" suggest that lift opposes gravity, aerodynamic lift can be in any direction. When an aircraft is in cruise for example, lift does oppose gravity. However, when the aircraft is climbing, descending, or banking in a turn, for example, the lift is tilted with respect to the vertical. Lift may also be entirely downwards in some aerobatic manoeuvres, or on the wing on a racing car. In this last case, the term downforce is often used.

The mathematical equations describing the generation of lift forces have been well established since the Wright Brothers experimentally determined a reasonably precise value for Smeaton's Smeaton coefficient more than 100 years ago, [1] but the practical explanation of what those equations mean is still controversial, with persistent misinformation and pervasive misunderstanding. [2]

Contents [hide]
1 Physical description of lift on an airfoil
1.1 Lift in an established flow
1.2 Stages of lift production
2 Methods of determining lift
2.1 Pressure integration
3 Mathematical approximations
3.1 Kutta–Joukowski theorem
3.2 1900 lift equation
4 Alternative Explanations
4.1 Equal transit-time
4.2 Coandă Effect
5 References
5.1 Notes
5.2 See also
5.3 Further reading
6 External links



[edit] Physical description of lift on an airfoil
Lift is generated in accordance with the fundamental principles of physics such as Newton's laws of motion, Bernoulli's principle, conservation of mass and the balance of momentum (where the latter is the fluid dynamics version of Newton's second law).[3] Each of these principles can be used to explain lift on an airfoil.[4] As a result, there are numerous different explanations with different levels of rigour and complexity. For example, there is an explanation based on Newton’s laws of motion; and an explanation based on Bernoulli’s principle. Neither of these explanations is incorrect, but each appeals to a different audience. [5]

To attempt a physical explanation of lift as it applies to an airplane, consider the flow around a 2-D, symmetric airfoil at positive angle of attack in a uniform free stream. Instead of considering the case where an airfoil moves through a flow as seen by a stationary observer, it is equivalent and simpler to consider the picture when the observer follows the airfoil and the flow moves past it.


[edit] Lift in an established flow

Streamlines around a NACA 0012 airfoil at moderate angle of attack.If one assumes that the flow naturally follows the shape of an airfoil, as is the usual observation, then the explanation of lift is rather simple and can be explained primarily in terms of pressures using Bernoulli's principle (which can be derived from Newton's second law) and conservation of mass, following the development by John D. Anderson in Introduction to Flight. [3]

The image to the right shows the streamlines over a NACA 0012 airfoil computed using potential flow theory, a simplified model of the real flow. The flow approaching an airfoil can be divided into two streamtubes, which are defined based on the area between streamlines. By definition, fluid never crosses a streamline; hence mass is conserved within each streamtube. One streamtube travels over the upper surface, while the other travels over the lower surface; dividing these two tubes is a dividing line that intersects the airfoil on the lower surface, typically near to the leading edge.

The upper stream tube constricts as it flows up and around the airfoil, the so-called upwash. From the conservation of mass, the flow speed must increase as the area of the stream tube decreases. Relatively speaking, the bottom of the airfoil presents less of an obstruction to the free stream, and often expands as the flow travels around the airfoil, slowing the flow below the airfoil. (Contrary to the equal transit-time explanation of lift, there is no requirement that particles that split as they travel over the airfoil meet at the trailing edge. It is typically the case that the particle traveling over the upper surface will reach the trailing edge long before the one traveling over the bottom.)

From Bernoulli's principle, the pressure on the upper surface where the flow is moving faster is lower than the pressure on the lower surface. The pressure difference thus creates a net aerodynamic force, pointing upward and downstream to the flow direction. The component of the force normal to the free stream is considered to be lift; the component parallel to the free stream is drag. In conjunction with this force by the air on the airfoil, by Newton's third law, the airfoil imparts an equal-and-opposite force on the surrounding air that creates the downwash. Measuring the momentum transferred to the downwash is another way to determine the amount of lift on the airfoil.


[edit] Stages of lift production
In attempting to explain why the flow follows the upper surface of the airfoil, the situation gets considerably more complex. To offer a more complete physical picture of lift, consider the case of an airfoil accelerating from rest in a viscous flow. Lift depends entirely on the nature of viscous flow past certain bodies[6]: in inviscid flow (i.e. assuming that viscous forces are negligible in comparison to inertial forces), there is no lift without imposing a net circulation.

When there is no flow, there is no lift and the forces acting on the airfoil are zero. At the instant when the flow is “turned on”, the flow is undeflected downstream of the airfoil and there are two stagnation points on the airfoil (where the flow velocity is zero): one near the leading edge on the bottom surface, and another on the upper surface near the trailing edge. The dividing line between the upper and lower streamtubes mentioned above intersects the body at the stagnation points. Since the flow speed is zero at these points, by Bernoulli's principle the static pressure at these points is at a maximum. As long as the second stagnation point is at its initial location on the upper surface of the wing, the circulation around the airfoil is zero and, in accordance with the Kutta–Joukowski theorem, there is no lift. The net pressure difference between the upper and lower surfaces is zero.

The effects of viscosity are contained within a thin layer of fluid called the boundary layer, close to the body. As flow over the airfoil commences, the flow along the lower surface turns at the sharp trailing edge and flows along the upper surface towards the upper stagnation point. The flow in the vicinity of the sharp trailing edge is very fast and the resulting viscous forces cause the boundary layer to accumulate into a vortex on the upper side of the airfoil between the trailing edge and the upper stagnation point.[7] This is called the starting vortex. The starting vortex and the bound vortex around the surface of the wing are two halves of a closed loop. As the starting vortex increases in strength the bound vortex also strengthens, causing the flow over the upper surface of the airfoil to accelerate and drive the upper stagnation point towards the sharp trailing edge. As this happens, the starting vortex is shed into the wake, [8] and is a necessary condition to produce lift on an airfoil. If the flow were stopped, there would be a corresponding "stopping vortex".[9] Despite being an idealization of the real world, the “vortex system” set up around a wing is both real and observable; the trailing vortex sheet most noticeably rolls up into wing-tip vortices.

The upper stagnation point continues moving downstream until it is coincident with the sharp trailing edge (a feature of the flow known as the Kutta condition). The flow downstream of the airfoil is deflected downward from the free-stream direction and, from the reasoning above in the basic explanation, there is now a net pressure difference between the upper and lower surfaces and an aerodynamic force is generated.


[edit] Methods of determining lift

[edit] Pressure integration
The force on the wing can be examined in terms of the pressure differences above and below the wing, which can be related to velocity changes by Bernoulli's principle.

The total lift force is the integral of vertical pressure forces over the entire wetted surface area of the wing:


where:

L is the lift,
A is the wing surface area
p is the value of the pressure,
n is the normal unit vector pointing into the wing, and
k is the vertical unit vector, normal to the freestream direction.
The above lift equation neglects the skin friction forces, which typically have a negligible contribution to the lift compared to the pressure forces. By using the streamwise vector i parallel to the freestream in place of k in the integral, we obtain an expression for the pressure drag Dp (which includes induced drag in a 3D wing). If we use the spanwise vector j, we obtain the side force Y.


One method for calculating the pressure is Bernoulli's equation, which is the mathematical expression of Bernoulli's principle. This method ignores the effects of viscosity, which can be important in the boundary layer and to predict friction drag, which is the other component of the total drag in addition to Dp.

The Bernoulli principle states that the sum total of energy within a parcel of fluid remains constant as long as no energy is added or removed. It is a statement of the principle of the conservation of energy applied to flowing fluids.

A substantial simplification of this proposes that as other forms of energy changes are inconsequential during the flow of air around a wing and that energy transfer in/out of the air is not significant, then the sum of pressure energy and speed energy for any particular parcel of air must be constant. Consequently, an increase in speed must be accompanied by a decrease in pressure and vice-versa. It should be noted that this is not a causational relationship. Rather, it is a coincidental relationship, whatever causes one must also cause the other as energy can neither be created nor destroyed. It is named for the Dutch-Swiss mathematician and scientist Daniel Bernoulli, though it was previously understood by Leonhard Euler and others.

Bernoulli's principle provides an explanation of pressure difference in the absence of air density and temperature variation (a common approximation for low-speed aircraft). If the air density and temperature are the same above and below a wing, a naive application of the ideal gas law requires that the pressure also be the same. Bernoulli's principle, by including air velocity, explains this pressure difference. The principle does not, however, specify the air velocity. This must come from another source, e.g., experimental data. Erroneous assumptions concerning velocity, e.g., that two parcels of air separated at the front of the wing must meet up again at the back of the wing, are commonly found.[10]

In order to solve for the velocity of inviscid flow around a wing, the Kutta condition must be applied to simulate the effects of inertia and viscosity. The Kutta condition allows for the correct choice among an infinite number of flow solutions that otherwise obey the laws of conservation of mass and conservation of momentum.


[edit] Mathematical approximations

[edit] Kutta–Joukowski theorem
Main article: Kutta–Joukowski theorem
Lift can be calculated using potential flow theory by imposing a circulation. It is often used by practicing aerodynamicists as a convenient quantity in calculations, for example thin-airfoil theory and lifting-line theory.

The circulation Γ is the line integral of the velocity of the air, in a closed loop around the boundary of an airfoil. It can be understood as the total amount of "spinning" (or vorticity) of air around the airfoil. The section lift/span L' can be calculated using the Kutta–Joukowski theorem:

L' = − ρVΓ
where ρ is the air density, V is the free-stream airspeed. The Helmholtz theorem states that circulation is conserved; put simply this is conservation of the air's angular momentum. When an aircraft is at rest, there is no circulation.

The challenge when using the Kutta–Joukowski theorem to determine lift is to determine the appropriate circulation for a particular airfoil. In practice, this is done by applying the Kutta condition, which uniquely prescribes the circulation for a given geometry and free-stream velocity.

A physical understanding of the theorem can be observed in the Magnus effect, which is a lift force generated by a spinning cylinder in a free stream. Here the necessary circulation is induced by the mechanical rotation acting on the boundary layer, causing it to separate at different points between top and bottom. The asymmetric separation then produces a circulation in the outer inviscid flow.


[edit] 1900 lift equation
The lift equation used by the Wright brothers was due to John Smeaton. It has the form:[11]


where:

L is the lift
k is the Smeaton coefficient- 0.005 (the drag of a 1 square foot plate at 1 mph)
Cl is the lift coefficient (the lift relative to the drag of a plate of the same area)
A is the area in square feet
The Wright brothers determined with wind tunnels that the Smeaton coefficient was incorrect and should have been 0.0033.[12]


[edit] Alternative Explanations

[edit] Equal transit-time

An illustration of the equal transit-time fallacy.One misconception encountered in a number of popular explanations of lift is the "equal transit time" fallacy. This fallacy assumes that the parcels of air that are divided above and below an airfoil must rejoin behind it. The fallacy states that because of the longer path of the upper surface of an airfoil, the air going over the top must go faster in order to "catch up" with the air flowing around the bottom.[13] Although it is true that the air moving over the top of a wing generating lift does move faster, there is no requirement for equal transit time. In fact the air moving over the top of an airfoil generating lift is always moving much faster than the equal transit theory would imply. [14]

A further flaw in this explanation is that it requires an airfoil to have thickness and curvature in order to create lift. In fact, thin flat plate wings and sails create lift under a range of angles of attack. If lift were solely a result of shape, then it would not be possible to fly inverted.

This explanation has gained currency by repetition in populist (rather than technical) books. At least one common pilot training book depicts the equal transit fallacy, adding to the confusion.[15]

Further information: List of works with the equal transit-time fallacy

[edit] Coandă Effect
Main article: Coandă effect
In a limited sense, the Coandă effect refers to the tendency of a fluid jet to stay attached to an adjacent surface that curves away from the flow and the resultant entrainment of ambient air into the flow. The effect is named for Henri Coandă, the Romanian aerodynamicist who exploited it in many of his patents. One first known uses is in his patent for a high-lift device [16] that uses a fan of gas exiting at high pressure from an internal compressor. This circular spray is directed radially over the top of a curved surface, shaped like a lens, to decrease the pressure on that surface. The total lift for the device is caused by the difference between this pressure and that on the bottom of the craft. Two Russian aircraft, the Antonov AN-72 and AN-74 "Coaler", use the exhaust from top-mounted jet engines flowing over the wing to enhance lift,[17] as do the prototype Boeing YC-14 and the McDonnell Douglas YC-15.[18] [19] The effect is also used in high-lift devices such as a blown flap.[20]

More broadly, some consider the effect to include the tendency of any fluid boundary layer to adhere to a curved surface, not just that involving a jet. It is in this broader sense that the Coandă effect is used by some to explain lift.[21] Jef Raskin[22], for example, describes a simple demonstration, using a straw to blow over the upper surface of a wing. The wing deflects upwards, thus supposedly demonstrating that the Coanda effect creates lift. This demonstration correctly demonstrates the Coandă effect as a fluid jet (the exhaust from a straw) adhering to a curved surface (the wing). However, the upper surface in this flow is a complicated, vortex-laden mixing layer, while on the the lower surface the flow is quiescent. The physics of this demonstration are very different from that off the general flow over the wing.[23] The usage in this sense is largely seen in popular references on aerodynamics.[21][22] Those in the aerodynamics field generally consider the Coanda effect in the more limited sense above[23][24][25] and use viscosity to explain why the boundary layer attaches to the surface of a wing.[9]


[edit] References

[edit] Notes
^ Crouch, Tom D. (1989). The Bishop's Boys : A Life of Wilbur and Orville Wright. W. W. Norton, pp. 220-226. ISBN 0-393-02660-4.
^ aerodave (2005-07-12). "How do airplanes fly, really? : A Staff Report by the Straight Dope Science Advisory Board". Chicago Reader, Inc.. Retrieved on 2007-02-18.
^ a b Anderson, John D. (2004), Introduction to Flight (5th ed.), McGraw-Hill, p. 355
^ NASA Glenn Research Center, Bernoulli and Newton, . Retrieved on 19 April 2008
^ Ison, David, "Bernoulli Or Newton: Who's Right About Lift?", Plane & Pilot, . Retrieved on 21 April 2008
^ Karamacheti, Krishnamurty (1980), Principles of Ideal-Fluid Aerodynamics (Reprint ed.)
^ Clancy, L.J., Aerodynamics, Figure 4.7
^ Clancy, L.J., Aerodynamics, Figure 4.8
^ a b White, Frank M. (2002), "Fluid Mechanics" (5th ed.), McGraw Hill
^ Aerodynamic Forces
^ Lift equation of the early 1900s
^ Failure Magazine-Wright Brothers
^ Anderson, David (2001). Understanding Flight. New York: McGraw-Hill. ISBN 0071363777. "The first thing that is wrong is that the principle of equal transit times is not true for a wing with lift."
^ Glenn Research Center (2006-03-15). "Incorrect Lift Theory". NASA. Retrieved on 2008-03-27.
^ Kershner, William K. (1979). The Student Pilot's Flight Manual, 5th ed.. ISBN 0-8138-1610-6.
^ USP No. 2108652
^ Antonov, Oleg Konstantinovich (24-May),
^ Neely, Mike (2008), . Retrieved on 21 July 2008
^ Pike, John (2008), . Retrieved on 23 July 2008
^ Englar, Robert J. (June 2005), "Overview of Circulation Control Pneumatic Aerodynamics: Blown Force and Moment Augmentation and Modification as Applied Primarily to Fixed-Wing Aircraft", Proceedings of the 2004 NASA/ONR Circulation Control Workshop, Part 1, NASA/ONR, pp. 37-99
^ a b Anderson, David & Eberhart, Scott (1999), How Airplanes Fly: A Physical Description of Lift, . Retrieved on 4 June 2008
^ a b Raskin, Jef (1994), Coanda Effect: Understanding Why Wings Work,
^ a b Auerbach, David (2000), "Why Aircraft Fly", Eur. J. Phys. 21: 289–296
^ Denker, JS, Fallacious Model of Lift Production, . Retrieved on 18 August 2008
^ Wille, R & Fernholz, H (1965), "Report on the first European Mechanics Colloquium, on the Coanda effect", J. Fluid Mech. 23: 801–819, doi:10.1017/S0022112065001702,

[edit] See also
Aerodynamic force
Angle of bank
Drag force
Lift-induced drag
Lift-to-drag ratio
Circulation control wing
Kutta condition
Kutta–Joukowski theorem
Drag
Downforce
Lifting-line theory

[edit] Further reading
Introduction to Flight, John D. Anderson, Jr., McGraw-Hill, ISBN 0-07-299071-6. The author is the Curator of Aerodynamics at the National Air & Space Museum Smithsonian Institute and Professor Emeritus at the University of Maryland.
Understanding Flight, by David Anderson and Scott Eberhardt, McGraw-Hill, ISBN 0-07-136377-7. The authors are a physicist and an aeronautical engineer. They explain flight in non-technical terms and specifically address the equal-transit-time myth. Turning of the flow around the wing is attributed to the Coanda effect, which is quite controversial.
Aerodynamics, Clancy, L.J. (1975), Section 4.8, Pitman Publishing Limited, London ISBN 0 273 01120 0
Quest for an improved explanation of lift Jaako Hoffren (Helsinki Univ. of Technology, Espoo, Finland) AIAA-2001-872 Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001 This paper focuses on a physics-based explanation of lift. Calculation of lift based on circulation with artificially imposed Kutta condition is interpreted as a mathematical model, having limited "real-world" physics, resulting from the assumption of potential flow. Also the role of viscosity is discussed. Author's claim is that viscosity is not important for lift generation.
Aerodynamics, Aeronautics, and Flight Mechanics, McCormick, Barnes W., (1979), Chapter 3, John Wiley & Sons, Inc., New York ISBN 0-471-03032-5
Fundamentals of Flight, Richard S. Shevell, Prentice-Hall International Editions, ISBN 0-13-332917-8. This book is primarily intended as a text for a one semester undergraduate course in mechanical or aeronautical engineering, although its sections on theory of flight are understandable with a passing knowledge of calculus and physics.

[edit] External links
Discussion of the apparent "conflict" between the various explanations of lift
NASA tutorial, with animation, describing lift
Explanation of Lift with animation of fluid flow around an airfoil
A treatment of why and how wings generate lift that focuses on pressure.
Physics of Flight - reviewed. Online paper by Prof. Dr. Klaus Weltner.
Explanation of Lift with animation of flow around an airfoil.
Retrieved from "http://en.wikipedia.org/wiki/Lift_(force)"


hahah

[jerm 0]

Quote

i use the annoying polyonmer thing -- because when your flying in a tunnel or relative to another flyer in the sky -- increasing your surface area of your wings (limbs) creates visual lift .

but as we are being pedantic

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.
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hahah

Clicky

Landing without injury is not necessarily evidence that you didn't fuck up... it just means you got away with it this time

[hparrish 0]

***this is an annoying misnomer that the tunnel world seems to have adopted, mean to increase drag, or more specifically, "increasing drag to lift you up"

Does anyone else grit their teeth when they hear this used? I know it's just tunnel jargon, but damnit, if you're using "flying" and "lift" in the same context there should be come continuity.

I know in relative terms it works, but people still think opening a parachute pops you up because of similar issues of relative speed/viewpoints, too.

***

Your either a skinny shit that never had to worry about it, or its been so long since you've learned how to freefly in a tunnel that you forgot.

But when your a big guy trying to learn in a tunnel at slow speed, you absolutely have to learn how to create lift to pop up off the net.

So grit your teeth and be annoyed all you want.

[hparrish 0]

I love how you can tell folks to piss off without saying piss off.

Too Funny.

[NeedToJump 0]

I'm really curious who responded to this poll saying freeflying in the tunnel does not help in the sky.

Freeflying in the tunnel absolutely does help freeflying in the sky as long as you are getting quality instruction. Sure, if you just jump into a wind tunnel and try to freefly without knowing what you are doing or having anyone help you, it probably won't help. But the same thing is true in the sky.

Freeflying in the tunnel and the sky are not the same, but the tunnel will definitely help. The more you do, the more it will help. Look at Derek Cox who was on the freefly world record with about 300 jumps. He still had to exit, dive to the formation and dock on it (I believe he was last out of the plane too.)

Everyone I know who has done freeflying in a tunnel has said it has helped them in the sky (and I know a LOT of people who have been freeflying in a wind tunnel.) I learned how to freefly in tunnels.

Wind Tunnel and Skydiving Coach http://www.ariperelman.com

[hparrish 0]

So far its 48 to 5, so I don't think it matters. No sense in trying to convert a lost cause.

[dzjnky 0]

The thing about tunnel learning is that you learn precision. It does take time, as others have mentioned, but if you put in the time consistently, your learning curve is much steeper (faster) than if you spread it out over many, many skydives. The skills you learn, and the feel for what the air does to your body, and what your body does to the air directly translates to the sky. Those skills allow you to easily compensate for the differences that the rig introduces when you go back to the sky. What I have found is that my ability to fly to a slot, and stop exactly where I want to stop, in exactly the orientation that I want has improved dramatically as a direct result of the time I have spent in the tunnel.

I think the tunnel helps a lot because of the immediate and direct visual feedback you get with the walls so close. You don't have any similar references on most skydives. There are differences - the rig, and also the fact that in the sky, you "strike a pose" and your fall rate adjusts to whatever drag you are producing. In the tunnel, you are given a windspeed, and you must find a way to create the correct amount of drag. This leads to a different way of flying, and in my opinion is one of the big reasons that first time tunnel flyers with many skydives have so much trouble. However, what you learn about flying in the tunnel is directly applicable to the sky, and in fact will dramatically increase your fall-rate range, especially in "slow flight" regimes, so if you do go low, your ability to "get back up" will be really improved. At least that is what I found.

And while I love the tunnel, there is still nothing like exiting at 13,000 ft or higher, and you can't fly a canopy in the tunnel... You also can't learn to fly a wingsuit in the tunnel - but that is a whole 'nuther discusson

[RackJR 0]

i can't believe there's a person who voted that the tunnel may hinder your abilities in freefall.

to me, that means the person has not experienced the tunnel, or perhaps did a couple minutes without coaching, didn't do very well, and then dismissed it as a tool for learning.

the tunnel will absolutely help your skills in freefall, for a variety of reasons, many of which are listed already.

but like most other things, experience is probably the best teacher. so give the tunnel an honest try. do a 15 minutes session with a qualified coach, and see what you think. try to keep in mind how long it would take you to learn the same things in the sky, 45 seconds at a time, with each 45 second learning opportunity separated from the next by however much time it takes you to pack and go back up on the next load. how expensive would 15 minutes worth of skydives be, with a qualified coach? 15 minutes of coached time in colorado is around $200. my freefly coach when i started jumping was $75/jump.

i've answered this question before, and i'm sure it will come up again. but once you start flying in a tunnel, you won't need to ask it any more. the answer will be so obvious that you'll wonder how it can keep being asked!!

Say what you mean. Do what you say.