Does the time-changing wing deformation contribute the enhancement of the lift for an insect? I have caculte the answer is 'Yes'.What do you thimk? Thanks ！

I dont think there is much calculation needed or indeed much thought. A 10 year old would be able to tell you the answer is yes.

Really? I am sure a 10 year old can tell you that wing 'motion' is the key to insect flight. But is the deformation of the wing (giving in to aero forces) more helping or hurting performance, as compared to undeformed rigid flapping? I don't know of any 10 year old who could answer that question on the spot. I am not even sure of the answer myself, without having done any research on rigid versus deformable flapping propulsion. So to all 10 year olds out there: What is the correct answer and explanation?

ok maybe not a 10 year old but but the hypothosis that changing the aerodynamic surfaces affects lift is not exactly a tricky one to reach.

Right, but that wasn't precisely the question. There sure is some effect. Now, is the effect of deformation favorable, i.e. 'enhancing performance' (increasing lift, decreasing drag), or unfavorable? If you believe in nature (and either evolution or creation) you will tend to think that there is a good reason for having flexible wings as opposed to stiff wings. Even so, is that simply for weight and energy savings while accepting some aero deficiencies, or is the flexibility actually helping aerodynamic performance? Can I answer that question without doing the research? Nope. (speaking for myself)

Has anyone, besides Hsu, done the research and found the answer to that question?

Well evolution would dictate that it is beneficial as it tends towards what gives improvement, not a trade off between efficiency and structural weight (im not mentioning creationism as it is clearly garbage and no one with a triple figure IQ could possibly believe it) so I would still say it is obvious as all flying creatures have flexible lifting surfaces (i.e. birds) indeed if the processes were available I'm sure aircraft would use much the same technology for lift and propulsion, indeed a cruder form is already in place (flaps, elevators, ailerons.....).

Nature did never come up with anything that rotates (with a bearing) - hence the invention of the wheel was such a big thing! Rotation, however, is crucial for aviation propulsion. Since nature does not have this it needs something else for propulsion. I can't see, why a deforming wing should not be a trade-off between weight and efficiency. Fair enough, I would guess as well that the deformation enhances the performance, but proving it with a few words isn't that easy. I assume adapting the wings to the change in AoA between upward and downward movement would have a big impact.

Btw. non flexible wings would look incredible silly for a bird - imagine it would want to get into a bird's house and keeps knocking its mates out of it ...

Ben mentioned:

(im not mentioning creationism as it is clearly garbage and no one with a triple figure IQ could possibly believe it)

diaw:

Well, Ben, without wanting to be contraversial ... *I* believe in a Creator (Intelligent Designer) & my IQ is actually pretty good...

Better to keep to technical discussions.

diaw...

I just cant work out how anybody with a rational logical mind can believe in a creator when there is no evidence to prove the "theory" especially scientists or engineers......

anyways back to the technical side.....

"...The human is so haughty thinking that can explain everything in the universe through their theories, logic, equations, etc..."

There are questions without answers and it's really good to keep our curiosity and creativity alive.

curiosity and creativity is one thing, fantasy is something else entirely

"If there were no God, it would be necessary to invent him" my favorite Voltaire quote, specifically because of the irony.

Here I'd paraphrase a great czech comedy, were simple country-cousin logger asked well-educated plastic surgery "do you believe in God, madame?" Rather similarly to Ben she replied with grin "I cann't understand how someone can believe in God when there's no evidence of him" That prime gross guy with "two-letter IQ" countered: "Though I haven't seen your tw*t I believe you have one"

Back to topic. Ben, you are obviously older than 10 and have tri-letter IQ, why you haven't answered the original question straighaway??? And as this is technical forum, you'd better explain us how it works in your opinion.

I've seen an animation of a butterfly "wind tunnel test". Watching the dye traces you could clearly see how wing motion corresponds to lift force variation. As well, you could see how the traces are deformed due to vortices creation and shedding. However, one could hardly decide whether those vortices increase or decrease the lift. Thus I really don't know and would prefer to go for some simulation to find the answer.

And as of wing material; remember that nature had to use deformable material as most of the animal wings had to be foldable. And that actually every material is deformable.Question may be whether the deformation is significant with respect to weight of the animal (it probabl is when talking about birds how when talking about flies, wasps etc..).

I think I addressed the question with the comment about evolution (that well proven idea) my point was simply that it is somewhat obvious that controlled deformation of a lifting surface is sure to improve the lift characteristics of the bird/insect as they have no other form of forward propulsion (a nasty bout of insect flatulence not withstanding) hence they must deform the wing to provide any static lift or forward thrust. Again a rigid wing structure would not be feasible for the animal would have to adjust the angle of attack so rapidly and to such a degree as to make the whole thing both improbable and most likely impossible (not to mention the resulting drag problem). Indeed the Wright brothers implemented the then revolutionary wing warping control system through an observation of birds. Surely this is obvious to anyone with the most rudimentary knowledge of fluid mechanics and aerodynamics. The reason that evolution (there's that nasty word again, run for the hills dubya) has produced that and intelligent design (i.e. us) cannot create the same effect in aircraft, is the muscle structure of the birds/insects, the effective power to weight ratio of the muscles allows such rapid controlled movement of the wing whilst not needing a muscle so bulky and heavy as to impede the flight.

As to the Czech comedy....I would base the assumption of the aforementioned object upon evidence based knowledge of women through careful study, not a blind assumption having never seen a woman before let alone studied her anatomy.

Legal disclaimer: I have nothing against personal religion, just organised religion, the wars it causes, the choices it removes, the laws it enforces and George Bush

The Massachusetts Institute of Technology has been involved for a number of years in studying the generation of lift/propulsion force in marine animals due to flexible body motion. Various researchers around the world have also looked at the flight of such creatures as dragonflies in order to determine the mechanism of flight. The unsteady nature of the flow coupled with the deformation of the wing can generate a tremendous amount of aerodynamic force - it is an interesting field of research. And while it may be obvious that a mechanism exists, understanding the interplay of boundary motion and unsteady flow is not at all "child's play".

Im sure I guess the interesting point is that any lift is benificial but the most important aspect is the control of the lift, hence why the wing deformation is probably the most influential characteristic of the of a birds/insects wing.

On a related point, I am sure I have seen some animations of LES study of deforming birds/insect wings (although it could just be my mind playing tricks) any ideas?

You still don't get the point, Ben.

>it is somewhat obvious that controlled deformation of a >lifting surface is sure to improve the lift >characteristics of the bird/insect as they have no other >form of forward propulsion

Simply not true. If you look at the motion of a fly wing you will recognize that it's comprised of a fair amount of rigid body motion (I hope you know what that means) plus some deformation. (Any motion can be described as RBM + deformation, as you learned in your undergrad dynamics class, and the deformation is not the dominant part in this case). Rigid body flapping alone would be enough to produce lift. It's not at all obvious whether the deformation adds to or subtracts from that.

Your idea of 'controlled deformation' is a product of your imagination and does not reflect reality with most insects and even birds. Typically, insect wings are deflected by aerodynamic forces, i.e. they 'cave in'. There are no muscles on an insect wing, rendering the poor creature unable to deform its wings, only flapping and rotating them by flexing the muscles attached at the root.

Likewise, a bird wing is driven by huge chest muscles, and even that motion can be largely described as rigid multi-body motion (wing segments rotating relative to each other), plus some feather bending. Some of that uncontrolled passive deformation has been SHOWN to be beneficial, like the feathers that stand up to passively affect separation on the wing, when a bird lands. However, to insist that it is 'obvious' that all deformation is beneficial, without being able to prove it, shows a lack of insight and scientific spirit.

I am often disappointed to see that a lot of people who take sides in the evolution vs. creationism debate have only a very limited lee-man's understanding of the basic concepts of evolution. And that goes for people on both sides!

Just because species evolve does not mean every single characteristic they own is good, beneficial, or even necessary and meaningful. Many phenotypes (if not most of them) are associated with relatively little selection pressure, being almost neutral.

Almost everything in life is a trade-off. It is very well possible that the passive deflection of a mosquito's wings leads to slightly lower aerodynamic efficiency, but has a lot of other advantages: Maneuverability, reliability, ability to withstand higher stresses without breaking, lower weight... and on... and on... and on...

Don't forget that there is more to life than aerodynamics, and have a good weekend...

Thanks, ag.

Finally an educated answer to the question!

I think the point is that the deformation is also a form of lift control, increasing and decreasing the lift locally to turn, climb, dive and also provide forward thrust. I was never claiming that the entirity of the wing is controlled by the bird (i.e. fethers) and I never argued that the rigid body motion(yes I know what it is) does not play a major part. I dont think the original point argued for either, the point was that time varying deformation of the wing (controlled or otherwise) was benificial. Which is what I argued for.

I'm not sure what the evolution point was about either, I never claimed the system was pefect (there are plenty of parts of my body that anoy me) indeed it is a reflection of the evolutionary system that all living things have parts that are not good. Indeed many parts are rendered useless through evolution as they once were but change of environment/needs dictates that their presence is no longer vital e.g. the apendix something that the human body no longer needs due to change of diet and its only visible effect is giving a fair percentage of it's owners apendicitis!

The early studies that I am familiar with actually didn't use CFD - they used simpler models to try to capture first-order effects of unsteadiness and vortex generation. A quick google reveals a number of results for unsteady dragonfly CFD, among them this paper

http://jeb.biologists.org/cgi/reprint/207/11/1887

The studies of marine animals that I reviewed years ago were by the Tryantafallous. If I'm not mistaken they built a robotic tuna not too many years ago based on their analytical work.

Ben wrote:

I just cant work out how anybody with a rational logical mind can believe in a creator when there is no evidence to prove the "theory" especially scientists or engineers......

diaw replies:

I would say that folks who believe in a Creator are in reasonable company if you consider that many of the fathers of science had similar views.

In my own personal view, I rely on my understanding of a Creator to identify & understand natural phenomena. If one understands that a Creator works/designs around the central principle of *order* (His nature & character), then it allows one to probe deeper along lines of order to identify patterns emerging out of apparent chaos.

Ben, this is a very personal viewpoint & I have been a believer for a long time. This is my personal perspective on what goes on around me. Not everyone has to agree - to each his own.

diaw...