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According to what is written it could be understood that there is two sources of induced drag: Due to lift generation( could be understood that it appears in 2-Dimentional flow) Due to tip effect (could be understood as 3-Dimentional since tip vortices are 3-d) the question is:
IF ANY ONE CAN HELP ME please mail me at mohamadcharif@yahoo.com —Preceding unsigned comment added by 193.227.168.132 ( talk) 08:28, 14 April 2004
The 2-D flow means the same as a wing od infinite span to chord ratio - and in this case the lift induced drag is zero.
In real 3-D case induced drag is the function Ci=(Cy)^2/Pi*A and is caused by the tip vortexes (mainly) and other trailing vortexes.
andrzejmat 16:13, 7 April 2006 (UTC)
I'm thinking of adding this, early in the article: "Lift induced drag is caused by the lift component of the wing being rotated backwards relative to the aircraft's motion, resulting in a drag component." Seem reasonable? Mat-C 16:31, 24 August 2005 (UTC)
I think a better simplification is: "Lift induced drag is caused by the lift component of the wing moving the air down behind the wing, resulting in a drag component." manfred.ullrich@arcor.de —Preceding unsigned comment added by 217.233.126.65 ( talk) 21:56, 20 October 2008 (UTC)
This is all technically incorrect and misleading. By DEFINITION lift is the component of the total force on the wing in the direction perpendicular to flight path. So, by definition, lift is always pointing upward. The more correct statement is to say that the total foce acting on the wing is slightly more tilted in the backward direction relative to the aircraft motion due to 3D effects, which results in greater drag. — Preceding
unsigned comment added by
67.252.29.252 (
talk)
04:05, 1 February 2014 (UTC)
"k is the factor by which the induced drag exceeds that of a wing of infinite span typically 1.05 to 1.15" is not true of course. Not" a wing of infinite span", but should be there "a wing of otimum (eliptical) planform."
andrzejmat 16:13, 7 April 2006 (UTC)
Agreed.-- FHBridges 17:12, 13 June 2006 (UTC)
In this I chose to Undo the immediately prior edit on the grounds: 1) The wingtip vortex is not the Source of induced drag, it is a manifestation of the spanwise flow which is the Source. 2) The later section of the Undone text essentially repeated what was previously said in the Section. While it is true that the energy content of the tip vortex is equal to the energy loss due to induced drag, and of mathematical value to the aerodynamicist, it is confusing to a lay reader to see two apparently conficting statements as to the source in the section 'Source'. Geoffrey Wickham 05:32, 9 October 2007 (UTC) Ref: 'Theory Of Flight', Richard Von Mises (Dover Books) sections VIII & IX. Geoffrey Wickham 05:51, 9 October 2007 (UTC)
Exactly, here is one citation about it: "Wingtip vortices are sometimes described as a component of induced drag, however this is incorrect. Though wingtip vortices do cause some drag, this drag is parasitic in nature. However, wingtip vortices also have the effect of destroying much of a wing's lift. Thus, in order to compensate for them, the wing must fly at a higher angle of attack, thereby causing more induced drag. The wingtip vortices do not directly cause induced drag though."-- Dajsinjo ( talk) 14:22, 6 February 2009 (UTC)
Are these statements in error?
(1) It is implied that it is possible to reduce induced drag without thereby reducing circulation, and thus lift, in this way: "Provide a physical barrier to vortex formation." It is my understanding (as a layman) that this is physically impossible--that preventing vortices would necessarily reduce circulation, and that since lift is proportional to circulation, this would reduce lift, defeating the purpose of a wing.
(2) It is suggested in the following that winglets, which have become commonplace, work by providing a physical barrier to vortex formaton: "More recent aircraft have wingtip mounted winglets to oppose the formation of vortices." It is my understanding that this is completely incorrect, and that winglets actually work by increasing effective aspect ratio (effective length of the wing) without increasing wingspan. Not by "creating a barrier to vortex formation", which, as I suggested above, would be self-defeating.
Could someone with knowledge of aerodynamics comment? —Preceding unsigned comment added by Mark.camp ( talk • contribs) 03:13, 11 August 2008 (UTC)
Is there where I should place this comment? Lift, by definition is perpendicular to the freestream velocity vector. The little introductory drawing and the second drawing should rather have the verticle arrow labeled lift. Lerabee ( talk) 03:42, 17 May 2009 (UTC)
The article says
Unlike parasitic drag, induced drag is inversely proportional to the square of the airspeed.
This is not strictly true. It has the unstated assumption that the lift coefficient is inversely proportional to the square of the airspeed. This is certainly true (only because the pilot actively makes it so) for an aircraft that is flying straight and level. It is not true for a wing at constant angle of attack with constant CL. I think the statement needs to be qualified (as well as the equations given below it about CL), or revised.
Perhaps this represents the difference between the mindsets of pilots and engineers =) MarcusMaximus ( talk) 10:05, 16 September 2008 (UTC)
Is there a way to relate the angle of attack to the variables in the drag equation? Obviously if you increase the angle of attack, the drag goes up - but where is that reflected in the equation? Fresheneesz ( talk) 23:35, 23 September 2008 (UTC)
-- Correction: " Ci=(Cy)^2/Pi*A " should be " Ci=(Cy)^2/Pi*A*e ", where "e" is the Oswald Efficiency Factor. For an elliptically loaded wing, e = 1, corresponding to the wing loading for minimum induced drag; for all other wing loadings, 0<e<1.
In the language of the article, "Cdi=(CL)^2*k/Pi*AR", k=1/e, and is a term corresponding to the efficiency of the wing. The difference is semantic, but in practice, most aerospace engineers tend to use the Oswald efficiency factor, and it is used in most aerodynamic textbooks (in the US), including the always popular aerodynamic text by Anderson.
Airplanenerd ( talk) 05:18, 6 April 2009 (UTC)
Cdi is given as K*Cl^2/Pi*AR. This is incorrect. The correct form is K*Cl^2 OR Cl^2/Pi*e*AR. This is because K = 1/Pi*e*AR. To clarify, Cdi= Induced drag Coefficient, K = drag polar constant, Cl = Coefficient of Lift, e = Oswald efficiency factor, and AR = aspect ratio. Mathiusdragoon ( talk) 14:40, 22 May 2009 (UTC)
I saw 206.55.186.247's changes and I liked them. I had been thinking about that change myself. Kinetic energy imparted into the downwash/vortex field is the fundamental source of induced drag. There's nothing magical, it's just an energy/power balance. When AR is infinite, there is no energy in the downwash/vortex field, and there is no induced drag.
Also, the "tilting lift vector" explanation is time-tested, but it's crap. It is akin to the "equal transit time" model. That is, it's right in some ways giving it the illusion of validity, but it's wrong in fundamental ways and it's incomplete. The tilted-lift vector begs more questions than it (supposedly) answers.
I'm still working this "correct & complete" understanding out in my own head. I've still got holes in my own understanding here (not in my head :-) ), The more we know, the more we know about what we don't know. I do know however, that much of this article as it stands is diversionary not explanatory. People can easily come away thinking they understand when they actually don't.
-- Gummer85 ( talk) 19:41, 29 May 2009 (UTC)
The result of the move request was: Move. Jafeluv ( talk) 17:25, 18 May 2010 (UTC)
Lift–induced drag → Lift-induced drag — This article was improperly moved from "Lift-induced drag" (with hyphen) to "Lift–induced drag" (with en dash), and the move needs to be reverted by an admin. "Lift-induced" here is simply a compound modifier, and there is no disjunction between "lift" and "induced"; in fact, there can't be because they're different parts of speech. Stephan Leeds ( talk) 01:12, 10 May 2010 (UTC)
This article went wrong at this edit http://en.wikipedia.org/?title=Lift-induced_drag&oldid=1383804 when the paragraph about wing tip vortexes was added. Wingtip vortexes do not cause drag, and span wise flow resulting in flow around the wing tip is a minor contribution to the twin vortexes which form behind the aircraft. The major contribution is lift itself. Lift is the result of the aircraft wing thrusting a large volume of air downward. (The manner in which this air is thrust downward by the wing is that the wing acts as an inclined plane. And this is the proper explanation of induced drag. The rest is distracting details about how it acts as an inclined plane.) The large volume of downward moving air in the midst of still air results in the vortexes at the boundaries between the moving and still air beginning at each wing tip and extending behind the aircraft. These vortexes would exist even in the absence of span wise flow around the wingtips, and they are responsible for the dissipation of ALL the power deposited into the air as a result of induced drag. They are not the cause of induced drag only the result of it. Any attempt to reduce these vortexes for a wing of given aspect ratio will either be achieved at the expense of lift (by reducing it) or will result in counter productive added weight and/or drag.
There is energy dissipation which is the result of span wise flow on the wing. Air subject to greater than ambient pressure under the wing will tend to flow out from under the wing in all directions including span wise toward the tip. Air subject to less than ambient pressure on top of the wing will tend to flow inward from all directions causing span wise flow from the wing tip. It can be seen from the geometry of this flow compared to the wing that the span wise flow reduces the effective angle of attack by increasing the effective chord of the wing relative to air flowing over the wing. Another way of looking at losses due to span wise flow is that it is momentum, and thus power imparted to the airflow which does not contribute to lift but decreases it instead. This is all that is needed to explain the loss of efficiency of a wing due to span wise flow over the wing surfaces. This wasted power is also dissipated in the vortexes created by the wing both at the wing tip as described and as vorticity created at the trailing edge of the wing as the span wise flow of the top of the wing meets the span wise flow of the bottom of the wing traveling in the opposite direction. Now here is where a wing tip treatment can do some good. Anything which will efficiently limit span wise flow or recover the momentum from it will improve the efficiency of a wing. This must be what effective wing tip treatments such as winglets are accomplishing. They're reducing the vortexes, but that is incidental to improving the wing performance by dealing with span wise flow.
In short, the large vortexes generated behind an aircraft wing are not the cause of drag on the wing, they are a result of it and they are the dissipation, or mixing, of the power deposited into the air near the wings with the bulk of the air nearby.
The effect of aspect ratio on wing efficiency can also be explained without reference to vortexes, and indeed vortexes have nothing to do with it:
f = ma where f is the component of the total force which acts perpendicular to the motion of the wing and, m is the mass of the air thrust downward by the wing, and a is the acceleration of the air thrust downward by the wing. The weight of the aircraft is equal to f.
v = at or a = v/t where t is the time the air thrust downward by the wing is in contact with the wing.
f = mv/t by substitution and thus we obtain
ft = mv or the relationship between impulse and momentum.
Now lets choose two aircraft of the same weight, with the same wing area traveling forward at the same speed. Let aircraft two have four times the wing aspect ratio of aircraft one which means that the wing chord of aircraft two will be one half that of aircraft one. Let's use capital letters for aircraft two since I don't want to bother with superscripts or subscripts. So;
F = f
T = t/2 since the speed is the same but the chord is 1/2 so MV = mv/2 or the momentum of the air thrust downward by aircraft two is 1/2 that of aircraft one. But how to apportion this difference among M and V? Even though it might seem that M = 2m because the span of aircraft two is twice that of aircraft one it seems more likely that M = m because V is likely = v/2 and so the depth of the air moved by aircraft two is 1/2 that of aircraft one - approximately.
So let's look at it from the perspective of energy.
e = mvv/2
E = MVV/2
if V = v/2 then
E = Mvv/8 = e/4
Energy over time is power p so P = p/4, but power is also force times velocity and the power forcing the air downward is the same power expended against induced drag so the induced drag of aircraft two is 1/4 that of aircraft one and by the small angle approximation the angle of attack of aircraft two is about 1/4 that of aircraft one. There you have the best explanation of why a higher aspect ratio wing is more efficient. You might also notice that 1/4 is the inverse of the difference in aspect ratio which agrees with the commonly accepted equation for induced drag. This has nothing to do with vortexes.
Now let's consider span wise flow. It seems clear to me that the same impulse - momentum - power argument can be made for the span wise flow based on the lesser chord of the wing on aircraft two so the higher aspect ratio wing will have less span wise flow losses as well and by a very similar proportion.
Notice that this discussion precludes vertical winglets on the tips of wings from acting to increase the aspect ratio of a wing. They can only have effect by reducing the inward span wise flow on top of the wing.
I did not add all this discussion to the article because I don't feel it belongs here. Parts of it probably belong in other articles. I put it here to make my point that this article should be reverted to the version just prior to http://en.wikipedia.org/?title=Lift-induced_drag&oldid=1383804 since that version is essentially correct, simple and to the point.
BTW, I got into this because I found that the "FAA Pilots Handbook of Aeronautical Information" also provides the bogus vortexes cause drag explanation, and I find that particularly embarrassing.—Preceding unsigned comment added by 71.216.55.126 ( talk) 04:58, 13 July 2010 (UTC)
Preceding added by me, 71.216.55.126, when I was not logged in. Rickanwp ( talk) 05:43, 13 July 2010 (UTC)
"Lift" is the component of the pressure-gradient force that is perpendicular to the relative wind; "Induced Drag" is the component that is parallel. The vector diagram at the beginning of the article labels the entire pressure vector as "Lift", which is just wrong. — Preceding unsigned comment added by 69.138.184.248 ( talk) 19:43, 13 August 2011 (UTC)
Is anyone actually reading this discussion? Helloooo? — Preceding unsigned comment added by 69.138.184.142 ( talk) 23:25, 24 December 2011 (UTC)
On 26 February User:GliderMaven edited this article, and also Drag (physics), by removing diagrams illustrating the origin of lift-induced drag. In the edit summary, GliderMavern wrote Removed diagrams are incorrect. Lift is perpendicular to flow, not to wing. Lift-induced drag is not what is shown in diagram, it’s a wingtip effect.
I have restored the diagrams and started this discussion so that interested Users can debate the accuracy or otherwise of the diagrams. Dolphin ( t) 03:00, 27 February 2012 (UTC)
Thanks for joining this discussion. I will add a reference or two for these diagrams in a few hours.
This diagram show two lift vectors – one is red and labelled Lift; and the other appears to be grey in color but it isn't labelled. It also shows two velocity vectors – one is red and labelled Effective Relative Airflow; and the other is blue and labelled Relative Airflow (Free Stream).
The red lift vector is perpendicular to the red velocity vector (Effective Relative Airflow). The grey lift vector is perpendicular to the blue velocity vector (Relative Airflow (Free Stream)). Neither lift vector is perpendicular to the chord line of the airfoil.
The angle between these pairs of vectors is correctly labelled the induced downwash angle ε.
You might recall the induced downwash angle ε is given by:
The coefficient of induced drag is given by:
Notice the similarity? The reason for the similarity is that the coefficient of induced drag is equal to the induced downwash angle multiplied by the wing lift coefficient. If the induced downwash angle disappears then induced drag also disappears. As the induced downwash angle increases, induced drag also increases. That is what diagrams of this kind are attempting to illustrate. Dolphin ( t) 04:05, 27 February 2012 (UTC)
@GliderMaven: JohnWalton created this diagram. In his post above he has invited you to explain the changes that you would make so that we can discuss the merits of those changes? Do you intend to explain your point of view so that JohnWalton can correct it? Dolphin ( t) 21:26, 28 February 2012 (UTC)
Hi guys. I have to agree with GliderMaven. I first saw that so-called "explanation" diagram in 1981 in Freshman "Intro to Aero" class. It was dubious then as it is now for many of the reasons given by GliderMaven. The problem is that it merely "feels" like an explanation while it actually connects nothing to nothing. It redefines "lift" as now somehow being not perpendicular to flow, and so on, and so on.
Induced drag comes from the adding of kinetic energy into the wake (conceptually, in speed perpendicular to the flow ("downward"), but also in the vortices in a way I don't fully get). This imparting of KE into the "downward" flow and vortices comes in association ("somehow" :-) ) with redistribution of pressure on the body. The change in pressure distribution results in forces in the aft flow direction which is the actual drag induced by the lift. The awful diagram purports (and has done so for decades) to give a physical connection between the production of lift and the subsequent induction of drag, but it does nothing except "induce" non critical thinkers into merely thinking they understand when they don't.
This diagram belongs in the trash heap along with that old "lift explanation" that says a molecule has to race around the top of an airfoil to meet up with its partner it split from at the leading edge. You know what I'm talking about.
As far as "reliable sources" go. If the diagram is from an otherwise reliable reference (and this diagram usually does appear in references that are otherwise reliable), that is not cause for inclusion. Reliability is determined by judgement of knowledgeable editors, there is just no other way to make that assessment. "Reliable sources" of the 1300's would have the sun going around the Earth, but we know better than to include it because we judge parts of those sources to be unreliable in light of what we know as editors. We would never include a diagram of the sun going around the Earth as an explanation of why day and night follow each other -- even if that 1300's source was otherwise mostly reliable in the light of modern days.
If we really want to make the article better, we need to find a source that eschews that crappy diagram for a more critical and modern explanation. I'm sure there is at least one out there.
Skyway ( talk) 20:49, 25 May 2012 (UTC)
By your leave, Dolphin. The talk page allows for some passion in argument. Witness: Your 4016-character investment in a response. Even then, it should have been obvious I was talking specifically about the diagram and its poor explanation, and that there was nothing personal about anyone or anyone's style. Indeed I had noted GliderMaven's "style" and ignored it in favor of attending to his actual point, which I thought was valid. Sorry I offended your sensibilities and that my Copernican example didn't sit well with you. Skyway ( talk) 19:52, 27 May 2012 (UTC)
I agree that the diagram is wrong, and I have removed it. There are several things wrong with it. If the vector labeled "L" is supposed to be the lift, then it's too long compared to "Leff", which is supposed to be the total force. And if the angle of attack (α) is zero, the downwash angle will still be non-zero (because the lift is positive), whereas this diagram makes it look as thought ε is always smaller than α. Also, the total force is not necessarily exactly perpendicular to the downwash direction, as implied by the diagram. I think a better diagram should be used, or else the caption should explain what is wrong with this one.
Eric Kvaalen (
talk)
08:52, 16 December 2013 (UTC)
Well, I see several things to remark on. First of all, it's true I didn't understand downwash to mean what you say. But what you have just written doesn't really correspond to how the Downwash article defines it (which I hadn't read). That article says it's the change in direction, which in your example would be 19°, not 1°.
I don't see why the force on the wing should be oriented 1° backwards if the air hits the wing going upwards at 9° and leaves going downwards at 10°. It seems to me the force should be oriented 0.5° backwards from vertical in that case (which would give a lift-to-drag ratio of about 115!).
Aren't you contradicting yourself when you say that the Kutta condition applies and then you say that the topside of the wing sees separated or even reverse flow? (The article Kutta condition has a couple sentences I don't understand: "If the trailing edge has a non-zero angle, the flow velocity there must be zero. At a cusped trailing edge, however, the velocity can be non-zero although it must still be identical above and below the airfoil. Another formulation is that the pressure must be continuous at the trailing edge.")
Why do you say that in 2D flow there is no downwash? Surely if you have a wing section of constant cross section spanning the width of a wind tunnel (so it's like 2D), it will still generate lift. But as I said on the 18th, a wing cannot cause a change in direction that is maintained forever as the air continues away from the wing.
Now, as to your version of the caption, you say the red vector is perpendicular to the airflow in the vicinity of the wing – but what is that? It changes from place to place!
You say it represents the lift on the airfoil section in two-dimensional flow at the same angle of attack. Why say 2D? And it's not the "lift", it's the total force.
Finally, you say the component of "Leff" parallel to the free stream is the induced drag on the wing. Well, actually it's the total drag isn't it? The induced drag is the total minus the drag you get when there's no lift.
By the way, I looked at your user page and saw a little box saying something silly about scientists, but that's off the subject!
Eric Kvaalen ( talk) 19:29, 23 December 2013 (UTC)
@Eric Kvaalen: Here are my suggested answers to some of your questions:
It can be a complex subject. I hope this is helpful. Dolphin ( t) 11:49, 25 December 2013 (UTC)
In the “Reducing induced drag” section, the statement “a high aspect ratio wing will produce less induced drag than a wing of low aspect ratio” is a common and persistent mistake in aeronautical circles. It is simply wrong. It can actually be deduced quite easily from the equation written in the very next section: “Calculation of induced drag”. There it can be seen that Di is apparently inversely proportional to S and to AR. But AR=b²/S, so in fact Di is inversely proportional to b² alone, and does not depend on S. So comparing two identical airplanes with: same weight, same speed, and same lift distribution (i.e. same e), the lower Di will be that of the plane with the longest wing span, regardless of having maybe a smaller AR, due to a sufficiently bigger S (bigger mean chord). [1] Enrico Lucarelli ( talk) 10:38, 5 December 2012 (UTC)
I'm with Enrico here. Aspect ratio only affects drag if the wing area is held constant, is the span varies. If aspect ratio is varied, but the span is held constant, the induced drag WILL STAY THE SAME. That is far from obvious in this article. I've had to explain this to numerous people who look at this article and think they can reduce Di by reducing the chord... Pictsidhe ( talk) 13:44, 17 July 2016 (UTC)
This thread was started more than 8 years ago but no significant change appears to have been made in response to the criticism by Enrico Lucarelli. Better late than never, I made some changes to reduce the emphasis on aspect ratio, and to remove some unsourced, non-encyclopaedic explanations of why induced drag occurs. See my diff. Dolphin ( t) 12:29, 19 May 2021 (UTC)
Am I summarising this correctly: Induced drag does not depend on aspect ratio. It does depend on span. So we should say it depends on span, with references. cagliost ( talk) 08:39, 27 May 2021 (UTC)
The edit made by 157.127.124.15 on 23 July 2012 states: "Of course the best way to reduce flow around the wingtip would be to have the winglet horizontal to provide lift from the extended wing, but this approach restricts the number of hangers that the aircraft may use."
The addition of this statement seems erratic in the context of the paragraph and conceptually wrong. Getting lift from this "horizontal winglet" would also generate induced drag. I might be able to accept a nonlifting airfoil as the horizontal winglet but this seems impractical, and would degredate lift on wing surfaces below the 'winglet'. I have been unable to find an example of this. Perhaps i'm interpretting this wrong.
lastly: "this approach restricts the number of hangers that the aircraft may use" - this is silly.
Thoughts? I'm going to remove this.
Viola00 ( talk) 20:16, 26 February 2013 (UTC)
I have done an edit comprising the following:
Eric Kvaalen ( talk) 08:52, 16 December 2013 (UTC)
1) I'm sorry, but you have your very own definition for induced drag, that is not the same it means in aerodynamics. Increase of drag above minimum for an wing spanning the full width of the windtunnel has nothing to do with induced drag, which is zero in that case.
2) Parasite drag is not constant, but depends on several factors, including angle of attack, but not amount of lift. Please see the second last paragraph onn this link: https://www.grc.nasa.gov/www/k-12/airplane/inclind.html link "Since the amount of drag generated at zero angle and the location of the stall point must usually be determined experimentally, aerodynamicists include the effects of inclination in the drag coefficient. But this presents an additional problem. There is another factor which affects the amount of drag produced by a finite wing. The effect is called induced drag or drag due to lift. The flow around the wing tips of a finite wing create an "induced" angle of attack on the wing near the tips. As the angle increases, the lift coefficient increases and this changes the amount of the induced drag. To separate the effects of angle of attack on drag, and drag due to lift, aerodynamicists often use two wing models. The wing model to determine angle of attack effects is long and thin, and may span the entire tunnel to produce a "two-dimensional" airfoil. Another model is used to determine the effects of the wing tips on the drag."
3) Your statement :"Maximum range occurs at the same airspeed as minimum drag (since energy equals force times distance)" would only be correct, if efficiency would remain the same, and that is a wrong assumption in general, and very far from the truth in case on jet aircrafts, propeller planes might be close enough as a rough approximation. In jets, the simplest approximation is assuming the thrust to be linearly related to fuel bur/hour, not the power. As a result, for jets the speed of minimum drag is significantly less than the speed of greatest range. 86.50.116.35 ( talk) 02:54, 3 July 2016 (UTC)
More recent aircraft have wingtip mounted winglets or wing fences to oppose the formation of vortices.
I removed the unreferenced mention of wing fences from the "Reducing induced drag" section. http://www.aerospaceweb.org/question/aerodynamics/q0228.shtml, referenced at wing fence, says fences create vortices to delay wing stall, but vortices also create drag. Can fences reduce induced drag? Burninthruthesky ( talk) 19:37, 2 May 2015 (UTC)
Hi, I'm trying to help improve this article, and I had a lot of changes reversed, which I understand because I made a lot of them.
So I'll just start with my questions, suggestions, changes one at a time to start the discussion.
I like the topic introduced in "Minimum induced drag for generic non-planar systems" section, and want to keep the final figure: "Nonplanar wings: results", with the text to introduce it. "Demasi Luciano et al discuss the efficiency of nonplanar wings. Here the efficiency is the ratio between its aerodynamic efficiency and the efficiency of a cantilevered wing with the same wing span and lift."<ref>
But the rest of the section seems to be a simple paste of a few paragraphs from a thesis/paper, and not at all in encyclopedic style or level. I propose the rest of this section be deleted. Any objections? Hess88 ( talk) 02:08, 15 April 2016 (UTC)
On 22 March 2022 Cagliost inserted a new section titled Effect of induced drag. This new section begins “A 2000 study found that for commercial airliners, induced drag was the second-largest component of total drag, at 37%.” Two sources are cited but no mention is made of page number or sub-section number etc.
This new section is incompatible with the rest of the article which is based on a classical analytical explanation of lift-induced drag and the manner in which it varies with lift coefficient. The article contains a useful diagram showing the way induced drag and parasitic drag combine to constitute total drag. It clearly shows that, at high speeds, induced drag is a diminishing component of total drag; and at low speeds, approaching the stall, induced drag approaches 100% of total drag. Clearly, the statement that induced drag is 37% of total drag is talking about something very different to what the majority of the article is talking about. Perhaps the 2000 study is addressing the overall economic cost of induced drag.
I have perused the two cited sources but I found nothing to support the new section. Readers wishing to verify the content of the new section shouldn’t have to read an entire source document to find that verification; it should be quickly accessible by navigating to the cited page number, sub-section etc.
In its present state, this new section is unsatisfactory. It might be possible for it to be improved to the point that it becomes satisfactory. If not, it should be removed. Dolphin ( t) 13:40, 23 March 2022 (UTC)
This famous diagram labels the backwards component of the aerodynamic reaction force "induced drag". However, isn't that wrong? I think this backwards component should be labelled "total drag". cagliost ( talk) 12:30, 25 March 2022 (UTC)
HI Cagliost. The article presently contains the sentence “A two-dimensional wing can still reduce drag for a given lift, by travelling faster and reducing its angle of attack, therefore reducing profile drag.” It is tagged “citation needed”. On 22 April you responded by providing an in-line citation pointing to a NASA web site. See your diff. Thanks for providing that.
I have perused the text you cited in support of the sentence but I can find nothing to support the sentence quoted above. If you still believe the NASA website contains some words that are truly relevant to the sentence in question, please let me know which words you have in mind. You can do so by quoting the words exactly, like this: “To separate the effects of angle of attack on drag, and drag due to lift, aerodynamicists often use two wing models.”
Secondly, I would appreciate your view on why you think a sentence dedicated to reducing profile drag deserves mention in a sub-section titled “Reducing induced drag”. Thanks. Dolphin ( t) 13:34, 23 April 2022 (UTC)
Disagree. The source provided, titled "Inclination Effects on Drag", clearly states "as angle increases, drag increases". It's relevant because lift-induced drag is not the only cause of the effect where (at slow speeds) drag decreases as speed increases. It's helpful to the reader to understand that there are other causes of this effect, otherwise they might be left with the impression that lift-induced drag is the only cause. cagliost ( talk) 11:40, 3 May 2022 (UTC)
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According to what is written it could be understood that there is two sources of induced drag: Due to lift generation( could be understood that it appears in 2-Dimentional flow) Due to tip effect (could be understood as 3-Dimentional since tip vortices are 3-d) the question is:
IF ANY ONE CAN HELP ME please mail me at mohamadcharif@yahoo.com —Preceding unsigned comment added by 193.227.168.132 ( talk) 08:28, 14 April 2004
The 2-D flow means the same as a wing od infinite span to chord ratio - and in this case the lift induced drag is zero.
In real 3-D case induced drag is the function Ci=(Cy)^2/Pi*A and is caused by the tip vortexes (mainly) and other trailing vortexes.
andrzejmat 16:13, 7 April 2006 (UTC)
I'm thinking of adding this, early in the article: "Lift induced drag is caused by the lift component of the wing being rotated backwards relative to the aircraft's motion, resulting in a drag component." Seem reasonable? Mat-C 16:31, 24 August 2005 (UTC)
I think a better simplification is: "Lift induced drag is caused by the lift component of the wing moving the air down behind the wing, resulting in a drag component." manfred.ullrich@arcor.de —Preceding unsigned comment added by 217.233.126.65 ( talk) 21:56, 20 October 2008 (UTC)
This is all technically incorrect and misleading. By DEFINITION lift is the component of the total force on the wing in the direction perpendicular to flight path. So, by definition, lift is always pointing upward. The more correct statement is to say that the total foce acting on the wing is slightly more tilted in the backward direction relative to the aircraft motion due to 3D effects, which results in greater drag. — Preceding
unsigned comment added by
67.252.29.252 (
talk)
04:05, 1 February 2014 (UTC)
"k is the factor by which the induced drag exceeds that of a wing of infinite span typically 1.05 to 1.15" is not true of course. Not" a wing of infinite span", but should be there "a wing of otimum (eliptical) planform."
andrzejmat 16:13, 7 April 2006 (UTC)
Agreed.-- FHBridges 17:12, 13 June 2006 (UTC)
In this I chose to Undo the immediately prior edit on the grounds: 1) The wingtip vortex is not the Source of induced drag, it is a manifestation of the spanwise flow which is the Source. 2) The later section of the Undone text essentially repeated what was previously said in the Section. While it is true that the energy content of the tip vortex is equal to the energy loss due to induced drag, and of mathematical value to the aerodynamicist, it is confusing to a lay reader to see two apparently conficting statements as to the source in the section 'Source'. Geoffrey Wickham 05:32, 9 October 2007 (UTC) Ref: 'Theory Of Flight', Richard Von Mises (Dover Books) sections VIII & IX. Geoffrey Wickham 05:51, 9 October 2007 (UTC)
Exactly, here is one citation about it: "Wingtip vortices are sometimes described as a component of induced drag, however this is incorrect. Though wingtip vortices do cause some drag, this drag is parasitic in nature. However, wingtip vortices also have the effect of destroying much of a wing's lift. Thus, in order to compensate for them, the wing must fly at a higher angle of attack, thereby causing more induced drag. The wingtip vortices do not directly cause induced drag though."-- Dajsinjo ( talk) 14:22, 6 February 2009 (UTC)
Are these statements in error?
(1) It is implied that it is possible to reduce induced drag without thereby reducing circulation, and thus lift, in this way: "Provide a physical barrier to vortex formation." It is my understanding (as a layman) that this is physically impossible--that preventing vortices would necessarily reduce circulation, and that since lift is proportional to circulation, this would reduce lift, defeating the purpose of a wing.
(2) It is suggested in the following that winglets, which have become commonplace, work by providing a physical barrier to vortex formaton: "More recent aircraft have wingtip mounted winglets to oppose the formation of vortices." It is my understanding that this is completely incorrect, and that winglets actually work by increasing effective aspect ratio (effective length of the wing) without increasing wingspan. Not by "creating a barrier to vortex formation", which, as I suggested above, would be self-defeating.
Could someone with knowledge of aerodynamics comment? —Preceding unsigned comment added by Mark.camp ( talk • contribs) 03:13, 11 August 2008 (UTC)
Is there where I should place this comment? Lift, by definition is perpendicular to the freestream velocity vector. The little introductory drawing and the second drawing should rather have the verticle arrow labeled lift. Lerabee ( talk) 03:42, 17 May 2009 (UTC)
The article says
Unlike parasitic drag, induced drag is inversely proportional to the square of the airspeed.
This is not strictly true. It has the unstated assumption that the lift coefficient is inversely proportional to the square of the airspeed. This is certainly true (only because the pilot actively makes it so) for an aircraft that is flying straight and level. It is not true for a wing at constant angle of attack with constant CL. I think the statement needs to be qualified (as well as the equations given below it about CL), or revised.
Perhaps this represents the difference between the mindsets of pilots and engineers =) MarcusMaximus ( talk) 10:05, 16 September 2008 (UTC)
Is there a way to relate the angle of attack to the variables in the drag equation? Obviously if you increase the angle of attack, the drag goes up - but where is that reflected in the equation? Fresheneesz ( talk) 23:35, 23 September 2008 (UTC)
-- Correction: " Ci=(Cy)^2/Pi*A " should be " Ci=(Cy)^2/Pi*A*e ", where "e" is the Oswald Efficiency Factor. For an elliptically loaded wing, e = 1, corresponding to the wing loading for minimum induced drag; for all other wing loadings, 0<e<1.
In the language of the article, "Cdi=(CL)^2*k/Pi*AR", k=1/e, and is a term corresponding to the efficiency of the wing. The difference is semantic, but in practice, most aerospace engineers tend to use the Oswald efficiency factor, and it is used in most aerodynamic textbooks (in the US), including the always popular aerodynamic text by Anderson.
Airplanenerd ( talk) 05:18, 6 April 2009 (UTC)
Cdi is given as K*Cl^2/Pi*AR. This is incorrect. The correct form is K*Cl^2 OR Cl^2/Pi*e*AR. This is because K = 1/Pi*e*AR. To clarify, Cdi= Induced drag Coefficient, K = drag polar constant, Cl = Coefficient of Lift, e = Oswald efficiency factor, and AR = aspect ratio. Mathiusdragoon ( talk) 14:40, 22 May 2009 (UTC)
I saw 206.55.186.247's changes and I liked them. I had been thinking about that change myself. Kinetic energy imparted into the downwash/vortex field is the fundamental source of induced drag. There's nothing magical, it's just an energy/power balance. When AR is infinite, there is no energy in the downwash/vortex field, and there is no induced drag.
Also, the "tilting lift vector" explanation is time-tested, but it's crap. It is akin to the "equal transit time" model. That is, it's right in some ways giving it the illusion of validity, but it's wrong in fundamental ways and it's incomplete. The tilted-lift vector begs more questions than it (supposedly) answers.
I'm still working this "correct & complete" understanding out in my own head. I've still got holes in my own understanding here (not in my head :-) ), The more we know, the more we know about what we don't know. I do know however, that much of this article as it stands is diversionary not explanatory. People can easily come away thinking they understand when they actually don't.
-- Gummer85 ( talk) 19:41, 29 May 2009 (UTC)
The result of the move request was: Move. Jafeluv ( talk) 17:25, 18 May 2010 (UTC)
Lift–induced drag → Lift-induced drag — This article was improperly moved from "Lift-induced drag" (with hyphen) to "Lift–induced drag" (with en dash), and the move needs to be reverted by an admin. "Lift-induced" here is simply a compound modifier, and there is no disjunction between "lift" and "induced"; in fact, there can't be because they're different parts of speech. Stephan Leeds ( talk) 01:12, 10 May 2010 (UTC)
This article went wrong at this edit http://en.wikipedia.org/?title=Lift-induced_drag&oldid=1383804 when the paragraph about wing tip vortexes was added. Wingtip vortexes do not cause drag, and span wise flow resulting in flow around the wing tip is a minor contribution to the twin vortexes which form behind the aircraft. The major contribution is lift itself. Lift is the result of the aircraft wing thrusting a large volume of air downward. (The manner in which this air is thrust downward by the wing is that the wing acts as an inclined plane. And this is the proper explanation of induced drag. The rest is distracting details about how it acts as an inclined plane.) The large volume of downward moving air in the midst of still air results in the vortexes at the boundaries between the moving and still air beginning at each wing tip and extending behind the aircraft. These vortexes would exist even in the absence of span wise flow around the wingtips, and they are responsible for the dissipation of ALL the power deposited into the air as a result of induced drag. They are not the cause of induced drag only the result of it. Any attempt to reduce these vortexes for a wing of given aspect ratio will either be achieved at the expense of lift (by reducing it) or will result in counter productive added weight and/or drag.
There is energy dissipation which is the result of span wise flow on the wing. Air subject to greater than ambient pressure under the wing will tend to flow out from under the wing in all directions including span wise toward the tip. Air subject to less than ambient pressure on top of the wing will tend to flow inward from all directions causing span wise flow from the wing tip. It can be seen from the geometry of this flow compared to the wing that the span wise flow reduces the effective angle of attack by increasing the effective chord of the wing relative to air flowing over the wing. Another way of looking at losses due to span wise flow is that it is momentum, and thus power imparted to the airflow which does not contribute to lift but decreases it instead. This is all that is needed to explain the loss of efficiency of a wing due to span wise flow over the wing surfaces. This wasted power is also dissipated in the vortexes created by the wing both at the wing tip as described and as vorticity created at the trailing edge of the wing as the span wise flow of the top of the wing meets the span wise flow of the bottom of the wing traveling in the opposite direction. Now here is where a wing tip treatment can do some good. Anything which will efficiently limit span wise flow or recover the momentum from it will improve the efficiency of a wing. This must be what effective wing tip treatments such as winglets are accomplishing. They're reducing the vortexes, but that is incidental to improving the wing performance by dealing with span wise flow.
In short, the large vortexes generated behind an aircraft wing are not the cause of drag on the wing, they are a result of it and they are the dissipation, or mixing, of the power deposited into the air near the wings with the bulk of the air nearby.
The effect of aspect ratio on wing efficiency can also be explained without reference to vortexes, and indeed vortexes have nothing to do with it:
f = ma where f is the component of the total force which acts perpendicular to the motion of the wing and, m is the mass of the air thrust downward by the wing, and a is the acceleration of the air thrust downward by the wing. The weight of the aircraft is equal to f.
v = at or a = v/t where t is the time the air thrust downward by the wing is in contact with the wing.
f = mv/t by substitution and thus we obtain
ft = mv or the relationship between impulse and momentum.
Now lets choose two aircraft of the same weight, with the same wing area traveling forward at the same speed. Let aircraft two have four times the wing aspect ratio of aircraft one which means that the wing chord of aircraft two will be one half that of aircraft one. Let's use capital letters for aircraft two since I don't want to bother with superscripts or subscripts. So;
F = f
T = t/2 since the speed is the same but the chord is 1/2 so MV = mv/2 or the momentum of the air thrust downward by aircraft two is 1/2 that of aircraft one. But how to apportion this difference among M and V? Even though it might seem that M = 2m because the span of aircraft two is twice that of aircraft one it seems more likely that M = m because V is likely = v/2 and so the depth of the air moved by aircraft two is 1/2 that of aircraft one - approximately.
So let's look at it from the perspective of energy.
e = mvv/2
E = MVV/2
if V = v/2 then
E = Mvv/8 = e/4
Energy over time is power p so P = p/4, but power is also force times velocity and the power forcing the air downward is the same power expended against induced drag so the induced drag of aircraft two is 1/4 that of aircraft one and by the small angle approximation the angle of attack of aircraft two is about 1/4 that of aircraft one. There you have the best explanation of why a higher aspect ratio wing is more efficient. You might also notice that 1/4 is the inverse of the difference in aspect ratio which agrees with the commonly accepted equation for induced drag. This has nothing to do with vortexes.
Now let's consider span wise flow. It seems clear to me that the same impulse - momentum - power argument can be made for the span wise flow based on the lesser chord of the wing on aircraft two so the higher aspect ratio wing will have less span wise flow losses as well and by a very similar proportion.
Notice that this discussion precludes vertical winglets on the tips of wings from acting to increase the aspect ratio of a wing. They can only have effect by reducing the inward span wise flow on top of the wing.
I did not add all this discussion to the article because I don't feel it belongs here. Parts of it probably belong in other articles. I put it here to make my point that this article should be reverted to the version just prior to http://en.wikipedia.org/?title=Lift-induced_drag&oldid=1383804 since that version is essentially correct, simple and to the point.
BTW, I got into this because I found that the "FAA Pilots Handbook of Aeronautical Information" also provides the bogus vortexes cause drag explanation, and I find that particularly embarrassing.—Preceding unsigned comment added by 71.216.55.126 ( talk) 04:58, 13 July 2010 (UTC)
Preceding added by me, 71.216.55.126, when I was not logged in. Rickanwp ( talk) 05:43, 13 July 2010 (UTC)
"Lift" is the component of the pressure-gradient force that is perpendicular to the relative wind; "Induced Drag" is the component that is parallel. The vector diagram at the beginning of the article labels the entire pressure vector as "Lift", which is just wrong. — Preceding unsigned comment added by 69.138.184.248 ( talk) 19:43, 13 August 2011 (UTC)
Is anyone actually reading this discussion? Helloooo? — Preceding unsigned comment added by 69.138.184.142 ( talk) 23:25, 24 December 2011 (UTC)
On 26 February User:GliderMaven edited this article, and also Drag (physics), by removing diagrams illustrating the origin of lift-induced drag. In the edit summary, GliderMavern wrote Removed diagrams are incorrect. Lift is perpendicular to flow, not to wing. Lift-induced drag is not what is shown in diagram, it’s a wingtip effect.
I have restored the diagrams and started this discussion so that interested Users can debate the accuracy or otherwise of the diagrams. Dolphin ( t) 03:00, 27 February 2012 (UTC)
Thanks for joining this discussion. I will add a reference or two for these diagrams in a few hours.
This diagram show two lift vectors – one is red and labelled Lift; and the other appears to be grey in color but it isn't labelled. It also shows two velocity vectors – one is red and labelled Effective Relative Airflow; and the other is blue and labelled Relative Airflow (Free Stream).
The red lift vector is perpendicular to the red velocity vector (Effective Relative Airflow). The grey lift vector is perpendicular to the blue velocity vector (Relative Airflow (Free Stream)). Neither lift vector is perpendicular to the chord line of the airfoil.
The angle between these pairs of vectors is correctly labelled the induced downwash angle ε.
You might recall the induced downwash angle ε is given by:
The coefficient of induced drag is given by:
Notice the similarity? The reason for the similarity is that the coefficient of induced drag is equal to the induced downwash angle multiplied by the wing lift coefficient. If the induced downwash angle disappears then induced drag also disappears. As the induced downwash angle increases, induced drag also increases. That is what diagrams of this kind are attempting to illustrate. Dolphin ( t) 04:05, 27 February 2012 (UTC)
@GliderMaven: JohnWalton created this diagram. In his post above he has invited you to explain the changes that you would make so that we can discuss the merits of those changes? Do you intend to explain your point of view so that JohnWalton can correct it? Dolphin ( t) 21:26, 28 February 2012 (UTC)
Hi guys. I have to agree with GliderMaven. I first saw that so-called "explanation" diagram in 1981 in Freshman "Intro to Aero" class. It was dubious then as it is now for many of the reasons given by GliderMaven. The problem is that it merely "feels" like an explanation while it actually connects nothing to nothing. It redefines "lift" as now somehow being not perpendicular to flow, and so on, and so on.
Induced drag comes from the adding of kinetic energy into the wake (conceptually, in speed perpendicular to the flow ("downward"), but also in the vortices in a way I don't fully get). This imparting of KE into the "downward" flow and vortices comes in association ("somehow" :-) ) with redistribution of pressure on the body. The change in pressure distribution results in forces in the aft flow direction which is the actual drag induced by the lift. The awful diagram purports (and has done so for decades) to give a physical connection between the production of lift and the subsequent induction of drag, but it does nothing except "induce" non critical thinkers into merely thinking they understand when they don't.
This diagram belongs in the trash heap along with that old "lift explanation" that says a molecule has to race around the top of an airfoil to meet up with its partner it split from at the leading edge. You know what I'm talking about.
As far as "reliable sources" go. If the diagram is from an otherwise reliable reference (and this diagram usually does appear in references that are otherwise reliable), that is not cause for inclusion. Reliability is determined by judgement of knowledgeable editors, there is just no other way to make that assessment. "Reliable sources" of the 1300's would have the sun going around the Earth, but we know better than to include it because we judge parts of those sources to be unreliable in light of what we know as editors. We would never include a diagram of the sun going around the Earth as an explanation of why day and night follow each other -- even if that 1300's source was otherwise mostly reliable in the light of modern days.
If we really want to make the article better, we need to find a source that eschews that crappy diagram for a more critical and modern explanation. I'm sure there is at least one out there.
Skyway ( talk) 20:49, 25 May 2012 (UTC)
By your leave, Dolphin. The talk page allows for some passion in argument. Witness: Your 4016-character investment in a response. Even then, it should have been obvious I was talking specifically about the diagram and its poor explanation, and that there was nothing personal about anyone or anyone's style. Indeed I had noted GliderMaven's "style" and ignored it in favor of attending to his actual point, which I thought was valid. Sorry I offended your sensibilities and that my Copernican example didn't sit well with you. Skyway ( talk) 19:52, 27 May 2012 (UTC)
I agree that the diagram is wrong, and I have removed it. There are several things wrong with it. If the vector labeled "L" is supposed to be the lift, then it's too long compared to "Leff", which is supposed to be the total force. And if the angle of attack (α) is zero, the downwash angle will still be non-zero (because the lift is positive), whereas this diagram makes it look as thought ε is always smaller than α. Also, the total force is not necessarily exactly perpendicular to the downwash direction, as implied by the diagram. I think a better diagram should be used, or else the caption should explain what is wrong with this one.
Eric Kvaalen (
talk)
08:52, 16 December 2013 (UTC)
Well, I see several things to remark on. First of all, it's true I didn't understand downwash to mean what you say. But what you have just written doesn't really correspond to how the Downwash article defines it (which I hadn't read). That article says it's the change in direction, which in your example would be 19°, not 1°.
I don't see why the force on the wing should be oriented 1° backwards if the air hits the wing going upwards at 9° and leaves going downwards at 10°. It seems to me the force should be oriented 0.5° backwards from vertical in that case (which would give a lift-to-drag ratio of about 115!).
Aren't you contradicting yourself when you say that the Kutta condition applies and then you say that the topside of the wing sees separated or even reverse flow? (The article Kutta condition has a couple sentences I don't understand: "If the trailing edge has a non-zero angle, the flow velocity there must be zero. At a cusped trailing edge, however, the velocity can be non-zero although it must still be identical above and below the airfoil. Another formulation is that the pressure must be continuous at the trailing edge.")
Why do you say that in 2D flow there is no downwash? Surely if you have a wing section of constant cross section spanning the width of a wind tunnel (so it's like 2D), it will still generate lift. But as I said on the 18th, a wing cannot cause a change in direction that is maintained forever as the air continues away from the wing.
Now, as to your version of the caption, you say the red vector is perpendicular to the airflow in the vicinity of the wing – but what is that? It changes from place to place!
You say it represents the lift on the airfoil section in two-dimensional flow at the same angle of attack. Why say 2D? And it's not the "lift", it's the total force.
Finally, you say the component of "Leff" parallel to the free stream is the induced drag on the wing. Well, actually it's the total drag isn't it? The induced drag is the total minus the drag you get when there's no lift.
By the way, I looked at your user page and saw a little box saying something silly about scientists, but that's off the subject!
Eric Kvaalen ( talk) 19:29, 23 December 2013 (UTC)
@Eric Kvaalen: Here are my suggested answers to some of your questions:
It can be a complex subject. I hope this is helpful. Dolphin ( t) 11:49, 25 December 2013 (UTC)
In the “Reducing induced drag” section, the statement “a high aspect ratio wing will produce less induced drag than a wing of low aspect ratio” is a common and persistent mistake in aeronautical circles. It is simply wrong. It can actually be deduced quite easily from the equation written in the very next section: “Calculation of induced drag”. There it can be seen that Di is apparently inversely proportional to S and to AR. But AR=b²/S, so in fact Di is inversely proportional to b² alone, and does not depend on S. So comparing two identical airplanes with: same weight, same speed, and same lift distribution (i.e. same e), the lower Di will be that of the plane with the longest wing span, regardless of having maybe a smaller AR, due to a sufficiently bigger S (bigger mean chord). [1] Enrico Lucarelli ( talk) 10:38, 5 December 2012 (UTC)
I'm with Enrico here. Aspect ratio only affects drag if the wing area is held constant, is the span varies. If aspect ratio is varied, but the span is held constant, the induced drag WILL STAY THE SAME. That is far from obvious in this article. I've had to explain this to numerous people who look at this article and think they can reduce Di by reducing the chord... Pictsidhe ( talk) 13:44, 17 July 2016 (UTC)
This thread was started more than 8 years ago but no significant change appears to have been made in response to the criticism by Enrico Lucarelli. Better late than never, I made some changes to reduce the emphasis on aspect ratio, and to remove some unsourced, non-encyclopaedic explanations of why induced drag occurs. See my diff. Dolphin ( t) 12:29, 19 May 2021 (UTC)
Am I summarising this correctly: Induced drag does not depend on aspect ratio. It does depend on span. So we should say it depends on span, with references. cagliost ( talk) 08:39, 27 May 2021 (UTC)
The edit made by 157.127.124.15 on 23 July 2012 states: "Of course the best way to reduce flow around the wingtip would be to have the winglet horizontal to provide lift from the extended wing, but this approach restricts the number of hangers that the aircraft may use."
The addition of this statement seems erratic in the context of the paragraph and conceptually wrong. Getting lift from this "horizontal winglet" would also generate induced drag. I might be able to accept a nonlifting airfoil as the horizontal winglet but this seems impractical, and would degredate lift on wing surfaces below the 'winglet'. I have been unable to find an example of this. Perhaps i'm interpretting this wrong.
lastly: "this approach restricts the number of hangers that the aircraft may use" - this is silly.
Thoughts? I'm going to remove this.
Viola00 ( talk) 20:16, 26 February 2013 (UTC)
I have done an edit comprising the following:
Eric Kvaalen ( talk) 08:52, 16 December 2013 (UTC)
1) I'm sorry, but you have your very own definition for induced drag, that is not the same it means in aerodynamics. Increase of drag above minimum for an wing spanning the full width of the windtunnel has nothing to do with induced drag, which is zero in that case.
2) Parasite drag is not constant, but depends on several factors, including angle of attack, but not amount of lift. Please see the second last paragraph onn this link: https://www.grc.nasa.gov/www/k-12/airplane/inclind.html link "Since the amount of drag generated at zero angle and the location of the stall point must usually be determined experimentally, aerodynamicists include the effects of inclination in the drag coefficient. But this presents an additional problem. There is another factor which affects the amount of drag produced by a finite wing. The effect is called induced drag or drag due to lift. The flow around the wing tips of a finite wing create an "induced" angle of attack on the wing near the tips. As the angle increases, the lift coefficient increases and this changes the amount of the induced drag. To separate the effects of angle of attack on drag, and drag due to lift, aerodynamicists often use two wing models. The wing model to determine angle of attack effects is long and thin, and may span the entire tunnel to produce a "two-dimensional" airfoil. Another model is used to determine the effects of the wing tips on the drag."
3) Your statement :"Maximum range occurs at the same airspeed as minimum drag (since energy equals force times distance)" would only be correct, if efficiency would remain the same, and that is a wrong assumption in general, and very far from the truth in case on jet aircrafts, propeller planes might be close enough as a rough approximation. In jets, the simplest approximation is assuming the thrust to be linearly related to fuel bur/hour, not the power. As a result, for jets the speed of minimum drag is significantly less than the speed of greatest range. 86.50.116.35 ( talk) 02:54, 3 July 2016 (UTC)
More recent aircraft have wingtip mounted winglets or wing fences to oppose the formation of vortices.
I removed the unreferenced mention of wing fences from the "Reducing induced drag" section. http://www.aerospaceweb.org/question/aerodynamics/q0228.shtml, referenced at wing fence, says fences create vortices to delay wing stall, but vortices also create drag. Can fences reduce induced drag? Burninthruthesky ( talk) 19:37, 2 May 2015 (UTC)
Hi, I'm trying to help improve this article, and I had a lot of changes reversed, which I understand because I made a lot of them.
So I'll just start with my questions, suggestions, changes one at a time to start the discussion.
I like the topic introduced in "Minimum induced drag for generic non-planar systems" section, and want to keep the final figure: "Nonplanar wings: results", with the text to introduce it. "Demasi Luciano et al discuss the efficiency of nonplanar wings. Here the efficiency is the ratio between its aerodynamic efficiency and the efficiency of a cantilevered wing with the same wing span and lift."<ref>
But the rest of the section seems to be a simple paste of a few paragraphs from a thesis/paper, and not at all in encyclopedic style or level. I propose the rest of this section be deleted. Any objections? Hess88 ( talk) 02:08, 15 April 2016 (UTC)
On 22 March 2022 Cagliost inserted a new section titled Effect of induced drag. This new section begins “A 2000 study found that for commercial airliners, induced drag was the second-largest component of total drag, at 37%.” Two sources are cited but no mention is made of page number or sub-section number etc.
This new section is incompatible with the rest of the article which is based on a classical analytical explanation of lift-induced drag and the manner in which it varies with lift coefficient. The article contains a useful diagram showing the way induced drag and parasitic drag combine to constitute total drag. It clearly shows that, at high speeds, induced drag is a diminishing component of total drag; and at low speeds, approaching the stall, induced drag approaches 100% of total drag. Clearly, the statement that induced drag is 37% of total drag is talking about something very different to what the majority of the article is talking about. Perhaps the 2000 study is addressing the overall economic cost of induced drag.
I have perused the two cited sources but I found nothing to support the new section. Readers wishing to verify the content of the new section shouldn’t have to read an entire source document to find that verification; it should be quickly accessible by navigating to the cited page number, sub-section etc.
In its present state, this new section is unsatisfactory. It might be possible for it to be improved to the point that it becomes satisfactory. If not, it should be removed. Dolphin ( t) 13:40, 23 March 2022 (UTC)
This famous diagram labels the backwards component of the aerodynamic reaction force "induced drag". However, isn't that wrong? I think this backwards component should be labelled "total drag". cagliost ( talk) 12:30, 25 March 2022 (UTC)
HI Cagliost. The article presently contains the sentence “A two-dimensional wing can still reduce drag for a given lift, by travelling faster and reducing its angle of attack, therefore reducing profile drag.” It is tagged “citation needed”. On 22 April you responded by providing an in-line citation pointing to a NASA web site. See your diff. Thanks for providing that.
I have perused the text you cited in support of the sentence but I can find nothing to support the sentence quoted above. If you still believe the NASA website contains some words that are truly relevant to the sentence in question, please let me know which words you have in mind. You can do so by quoting the words exactly, like this: “To separate the effects of angle of attack on drag, and drag due to lift, aerodynamicists often use two wing models.”
Secondly, I would appreciate your view on why you think a sentence dedicated to reducing profile drag deserves mention in a sub-section titled “Reducing induced drag”. Thanks. Dolphin ( t) 13:34, 23 April 2022 (UTC)
Disagree. The source provided, titled "Inclination Effects on Drag", clearly states "as angle increases, drag increases". It's relevant because lift-induced drag is not the only cause of the effect where (at slow speeds) drag decreases as speed increases. It's helpful to the reader to understand that there are other causes of this effect, otherwise they might be left with the impression that lift-induced drag is the only cause. cagliost ( talk) 11:40, 3 May 2022 (UTC)