Re: OT: Secrets of bee flight revealed
Ok, I stand corrected. Harry William Beaty wrote: > On Wed, 7 Dec 2005, Harry Veeder wrote: >> >> William Beaty wrote: >>> But I already know the answer. It's simple: Pressure differentials >>> explain 100% of the lifting force, while flow-deflection (the acceleration >>> of fluid masses) also explains 100% of the lifting force. These are >>> simply two independant ways of attacking the problem. There is no >>> competition between a "Bernoulli" viewpoint and a "Newton" viewpoint. >>> This is just another way of saying that the Bernoulli equation ends up >>> obeying Newton's laws. Or in other words, if the water is deflected, >>> there MUST be a pressure differential which causes a lifting force... and >>> if there is a lifting force, then the water MUST be deflected. >> >> I don't think the two explanations are equivalent. >> During level flight the Bernoulli explanation DOES NOT predict that >> the fluid leaving the wing tip will be directed downwards. > > On the contrary, in 3D flight the Bernoulli explanation *requires* that > fluid leaving the wing tip be deflected downwards. That's the reason for > sharp trailing edges, the reason that cambered airfoils give lift at zero > attack, and it's the whole point of the "Kutta Condition." > > But there's also a wrong explanation that wormed its way into many books, > and explanation which depicts the air flowing horizontally off the > trailing edge of an untilted wing. The diagram is wrong, and real wings > only do such a thing when adjusted to give zero lifting force. The > diagrams showing undeflected air are certainly not the "Bernoulli > explanation." The wrong explanation has become known as the "Popular > explanation" or the "equal transit-time fallacy" in order to distinguish > it from the "Bernoulli explanation." > > In other words... since an airfoil always deflects air downwards from its > trailing edge in order to generate a lifting force, then all correct > explanations of airfoil function will include the downward deflection of > air as part of the explanation. > > > (( ( ( ( ((O)) ) ) ) ))) > William J. BeatySCIENCE HOBBYIST website > billb at amasci com http://amasci.com > EE/programmer/sci-exhibits amateur science, hobby projects, sci fair > Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci >
RE: OT: Secrets of bee flight revealed
On Wed, 7 Dec 2005, Rick Monteverde wrote: > >But the incoming air will fill the vacuum chamber, with > >the wave travelling at roughly the speed of sound! > >In human time scale, as soon as you open the valve > >and generate an air jet, significant air pressure > >appears on the OTHER side of the wing. You can't > >just claim that the pressure there is insignificant, > >instead you have to measure it, millisecond by millisecond. > > The pump is large compared to the small jar volume, and once that dense > air in the jet disperses, which it does very quickly, density and > pressure get pretty low pretty fast before much of it swirls around > underneath the foil. To see it and its scale is convincing. Seeing my > writing about it isn't. Eh. Seeing the demonstration wouldn't convince me, since my brain would insist that "SINCE the airfoil is deflected upwards, THEREFORE the pressure underneath is greater than the pressure above." :) > > >If you can show that air can PULL on a curved wing > >(i.e. create an absolute negative pressure,) > >that's something very interesting. > > Yup. It's been shown too, but not by me. Google should bring it up with > words like van der Waals, airfoil, boundary layer, etc. But that's just lowered pressure, not absolute negative (attraction) pressure. Boundary layer stuff is weird, but I've never seen articles talking about negative gas pressure. It's hard to see how a molecule, by colliding with a surface, could *attract* that surface. And it's hard to see how widely separated molecules could attract each other on average, especially if they're moving fast enough to bounce during collisions (which would create a strong repulsion force which would have to be canceled out by any attraction mechanism.) If they don't bounce during collisions, then that's called condensation. :) > Why else would a > flow stick against a surface and follow it down around a curve like > that? For air jets in air, or for water jets underwater, Coanda Effect explains it: air flows always entrain adjacent air, pulling the adjacent air into the flow. Or said another way, flows always represent lower pressure, so if air is flowing parallel to an object, the perpendicular force between the flow and the object will be reduced, causing the flow and the object to accelerate towards each other as the outer (non-flowing) air exerts its non-reduced pressure. Blow some air parallel to one side of a dangling piece of paper and the paper will be pushed into the flow so it "adheres" to the flow. And the flow will "stick" to the paper, bending away from it's original trajectory. Separate topic: In that old SciAm article about Coanda Effect, they found that tiny structures within the boundary layer could have large effects, so a small step or striation on the surface would make the flow-adhesion effect stronger. I remember one oddity from conventional textbooks: if you put a polished sphere in a wind tunnel, the smoke will curve around the sphere and follow the back of the sphere for quite a ways before "detaching" and becoming turbulent... but if you add a small disk of thin sandpaper (or even roughened paint) to the very front of the sphere, the smoke then detaches right at the circumference of the sphere, and it won't follow the curve around to the back of the sphere at all. Just that tiny change to the front of the sphere will put the entire rear of the sphere into "stall mode." Aircraft designers know all about the effect: just a small bit of rough ice on the leading edge and top of an aircraft wing will trigger early flow-detachment, ruining the lift and leading to crashes on takeoff. That's why they're so paranoid about "de-icing" the tops of airliner wings. The airfoil bottoms are mostly irrelevant (and you can even hang huge fuel tanks and racks of missles down there.) Also there's a whole group of experimental aircraft hobbyists who specialize in high-lift "laminar flow" wings with highly polished upper surfaces. These aren't widely used because their characteristics are seriously altered by a small bit of raindrops clinging to the wing. > > I never finished construction on it, but I started a rig where the > airfoil sat on a membrane with good vacuum under the membrane in a > separate chamnber from the air above the foil. Air jet would hit the top > of the foil as before, but the whole bottom side would be against the > membrane. Pump would keep the air above at as low a pressure as possible > while the jet shot across the foil surface. Now THAT would be more convincing (even more convincing that measuring the pressure under your first airfoil.) > I figure the foil would > still rise into the airflow, pulling up on the membrane with the > certain-to-be-lower pressure below it. > > Maybe simpler to use a split chamber with water instead of air? Or use an oil stream in a vacuum? But then you might get genuinely negative fluid pressure, the same negative pressure that's the s
Re: OT: Secrets of bee flight revealed
On Wed, 7 Dec 2005, Harry Veeder wrote: > > William Beaty wrote: > > But I already know the answer. It's simple: Pressure differentials > > explain 100% of the lifting force, while flow-deflection (the acceleration > > of fluid masses) also explains 100% of the lifting force. These are > > simply two independant ways of attacking the problem. There is no > > competition between a "Bernoulli" viewpoint and a "Newton" viewpoint. > > This is just another way of saying that the Bernoulli equation ends up > > obeying Newton's laws. Or in other words, if the water is deflected, > > there MUST be a pressure differential which causes a lifting force... and > > if there is a lifting force, then the water MUST be deflected. > > I don't think the two explanations are equivalent. > During level flight the Bernoulli explanation DOES NOT predict that > the fluid leaving the wing tip will be directed downwards. On the contrary, in 3D flight the Bernoulli explanation *requires* that fluid leaving the wing tip be deflected downwards. That's the reason for sharp trailing edges, the reason that cambered airfoils give lift at zero attack, and it's the whole point of the "Kutta Condition." But there's also a wrong explanation that wormed its way into many books, and explanation which depicts the air flowing horizontally off the trailing edge of an untilted wing. The diagram is wrong, and real wings only do such a thing when adjusted to give zero lifting force. The diagrams showing undeflected air are certainly not the "Bernoulli explanation." The wrong explanation has become known as the "Popular explanation" or the "equal transit-time fallacy" in order to distinguish it from the "Bernoulli explanation." In other words... since an airfoil always deflects air downwards from its trailing edge in order to generate a lifting force, then all correct explanations of airfoil function will include the downward deflection of air as part of the explanation. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
Let me rephrase myself. Elevators only generate lift by changing the pitch angle upward because the tail is pushed down when the elevators tilt up. Harry Rick Monteverde wrote: > Harry - > > If you change your pitch angle upward, you get an increased angle of > attack on the wings, at least initially depending on what you allow to > happen with airspeed and power settings. As angle of attack increases, > so does lift increase (and drag)- up to the region where aerodynamic > stall begins. This is very basic. > > -Original Message- > From: Harry Veeder [mailto:[EMAIL PROTECTED] > Sent: Monday, December 12, 2005 4:57 PM > To: vortex-l@eskimo.com > Subject: Re: OT: Secrets of bee flight revealed > > > Ok. I was confusing the effect of elevator movement with the effect of > flap movement. Up turned elevators tilt the nose up, but they do not > increase the lift. > > Harry > > Rick Monteverde wrote: > >> That's pitch control dynamics, and I think you've got it backwards. >> Flaps don't turn up, but ailerons do. And when an aileron goes up, >> that wing goes down. Putting ailerons on both wings up at once would >> most likely make the plane go down, all other factors constant. >> >> - Rick >> >> -Original Message- >> From: Harry Veeder [mailto:[EMAIL PROTECTED] >> Sent: Monday, December 12, 2005 9:58 AM >> To: vortex-l@eskimo.com >> Subject: Re: OT: Secrets of bee flight revealed >> >> >> Rick, >> >> Ok thanks...sorry about my slow response. >> If this effect is the primary cause of lift then if the flaps on the >> wing of a plane are turned up then you would expect the plane to >> descend. Instead a plane will climb. >> >> Harry >> >> Rick Monteverde wrote: >> >>> Harry - >>> >>> I did the vacuum experiment years ago so details are a little hazy, >>> but basically it was a jar with a small diameter (1/8" I.D. I >>> think)tube sticking through the lid. Inside the jar was a small >>> airfoil section made of modelling clay, suspended vertically with the > >>> tube pointing at the front/top surface. Basically like the >>> spoon/faucet setup, but with an air jet instead of a faucet. Vacuum >>> pump is high capacity relative to the small air inlet capacity, so >>> when allowing air to flow in through the tube, the vacuum still stays > >>> fairly high - so all the significant air action is just the flow >>> hitting the top side of the foil. The foil pulls into the airflow, >>> just like the spoon in a water flow. And I'm pretty sure, mitigated >>> by >> >>> the absence of any real measurement, that the pressure on the top of >>> the foil was mostly higher than on the bottom. >>> >>> - Rick >> >> >> >> >> > > > > >
RE: OT: Secrets of bee flight revealed
Harry - If you change your pitch angle upward, you get an increased angle of attack on the wings, at least initially depending on what you allow to happen with airspeed and power settings. As angle of attack increases, so does lift increase (and drag)- up to the region where aerodynamic stall begins. This is very basic. -Original Message- From: Harry Veeder [mailto:[EMAIL PROTECTED] Sent: Monday, December 12, 2005 4:57 PM To: vortex-l@eskimo.com Subject: Re: OT: Secrets of bee flight revealed Ok. I was confusing the effect of elevator movement with the effect of flap movement. Up turned elevators tilt the nose up, but they do not increase the lift. Harry Rick Monteverde wrote: > That's pitch control dynamics, and I think you've got it backwards. > Flaps don't turn up, but ailerons do. And when an aileron goes up, > that wing goes down. Putting ailerons on both wings up at once would > most likely make the plane go down, all other factors constant. > > - Rick > > -Original Message- > From: Harry Veeder [mailto:[EMAIL PROTECTED] > Sent: Monday, December 12, 2005 9:58 AM > To: vortex-l@eskimo.com > Subject: Re: OT: Secrets of bee flight revealed > > > Rick, > > Ok thanks...sorry about my slow response. > If this effect is the primary cause of lift then if the flaps on the > wing of a plane are turned up then you would expect the plane to > descend. Instead a plane will climb. > > Harry > > Rick Monteverde wrote: > >> Harry - >> >> I did the vacuum experiment years ago so details are a little hazy, >> but basically it was a jar with a small diameter (1/8" I.D. I >> think)tube sticking through the lid. Inside the jar was a small >> airfoil section made of modelling clay, suspended vertically with the >> tube pointing at the front/top surface. Basically like the >> spoon/faucet setup, but with an air jet instead of a faucet. Vacuum >> pump is high capacity relative to the small air inlet capacity, so >> when allowing air to flow in through the tube, the vacuum still stays >> fairly high - so all the significant air action is just the flow >> hitting the top side of the foil. The foil pulls into the airflow, >> just like the spoon in a water flow. And I'm pretty sure, mitigated >> by > >> the absence of any real measurement, that the pressure on the top of >> the foil was mostly higher than on the bottom. >> >> - Rick > > > > >
Re: OT: Secrets of bee flight revealed
Ok. I was confusing the effect of elevator movement with the effect of flap movement. Up turned elevators tilt the nose up, but they do not increase the lift. Harry Rick Monteverde wrote: > That's pitch control dynamics, and I think you've got it backwards. > Flaps don't turn up, but ailerons do. And when an aileron goes up, that > wing goes down. Putting ailerons on both wings up at once would most > likely make the plane go down, all other factors constant. > > - Rick > > -Original Message- > From: Harry Veeder [mailto:[EMAIL PROTECTED] > Sent: Monday, December 12, 2005 9:58 AM > To: vortex-l@eskimo.com > Subject: Re: OT: Secrets of bee flight revealed > > > Rick, > > Ok thanks...sorry about my slow response. > If this effect is the primary cause of lift then if the flaps on the > wing of a plane are turned up then you would expect the plane to > descend. Instead a plane will climb. > > Harry > > Rick Monteverde wrote: > >> Harry - >> >> I did the vacuum experiment years ago so details are a little hazy, >> but basically it was a jar with a small diameter (1/8" I.D. I >> think)tube sticking through the lid. Inside the jar was a small >> airfoil section made of modelling clay, suspended vertically with the >> tube pointing at the front/top surface. Basically like the >> spoon/faucet setup, but with an air jet instead of a faucet. Vacuum >> pump is high capacity relative to the small air inlet capacity, so >> when allowing air to flow in through the tube, the vacuum still stays >> fairly high - so all the significant air action is just the flow >> hitting the top side of the foil. The foil pulls into the airflow, >> just like the spoon in a water flow. And I'm pretty sure, mitigated by > >> the absence of any real measurement, that the pressure on the top of >> the foil was mostly higher than on the bottom. >> >> - Rick > > > > >
RE: OT: Secrets of bee flight revealed
That's pitch control dynamics, and I think you've got it backwards. Flaps don't turn up, but ailerons do. And when an aileron goes up, that wing goes down. Putting ailerons on both wings up at once would most likely make the plane go down, all other factors constant. - Rick -Original Message- From: Harry Veeder [mailto:[EMAIL PROTECTED] Sent: Monday, December 12, 2005 9:58 AM To: vortex-l@eskimo.com Subject: Re: OT: Secrets of bee flight revealed Rick, Ok thanks...sorry about my slow response. If this effect is the primary cause of lift then if the flaps on the wing of a plane are turned up then you would expect the plane to descend. Instead a plane will climb. Harry Rick Monteverde wrote: > Harry - > > I did the vacuum experiment years ago so details are a little hazy, > but basically it was a jar with a small diameter (1/8" I.D. I > think)tube sticking through the lid. Inside the jar was a small > airfoil section made of modelling clay, suspended vertically with the > tube pointing at the front/top surface. Basically like the > spoon/faucet setup, but with an air jet instead of a faucet. Vacuum > pump is high capacity relative to the small air inlet capacity, so > when allowing air to flow in through the tube, the vacuum still stays > fairly high - so all the significant air action is just the flow > hitting the top side of the foil. The foil pulls into the airflow, > just like the spoon in a water flow. And I'm pretty sure, mitigated by > the absence of any real measurement, that the pressure on the top of > the foil was mostly higher than on the bottom. > > - Rick
Re: OT: Secrets of bee flight revealed
Rick, Ok thanks...sorry about my slow response. If this effect is the primary cause of lift then if the flaps on the wing of a plane are turned up then you would expect the plane to descend. Instead a plane will climb. Harry Rick Monteverde wrote: > Harry - > > I did the vacuum experiment years ago so details are a little hazy, but > basically it was a jar with a small diameter (1/8" I.D. I think)tube > sticking through the lid. Inside the jar was a small airfoil section > made of modelling clay, suspended vertically with the tube pointing at > the front/top surface. Basically like the spoon/faucet setup, but with > an air jet instead of a faucet. Vacuum pump is high capacity relative to > the small air inlet capacity, so when allowing air to flow in through > the tube, the vacuum still stays fairly high - so all the significant > air action is just the flow hitting the top side of the foil. The foil > pulls into the airflow, just like the spoon in a water flow. And I'm > pretty sure, mitigated by the absence of any real measurement, that the > pressure on the top of the foil was mostly higher than on the bottom. > > - Rick
Re: OT: Secrets of bee flight revealed
Ok, time to wade through and clarify... (will try to snip tyhe unimportant) --- William Beaty <[EMAIL PROTECTED]> wrote: > On Tue, 6 Dec 2005, Merlyn wrote: > > > I don't agree with Bernoulli, but pressure is > still > > the key. > > First see: http://amasci.com/wing/airfoil.html, and > especially the FAQ at > http://amasci.com/wing/airfoil.html#faq > Which is basically what I was saying, but explained much better. > > > As the wing pushes through the air, the leading > edge > > divides the air into roughly equivalent parts > flowing > > above and below. > > Nope, doesn't happen. When the pattern of air > flowing above and below the > wing are the same, then the lift is zero. For > example, here's a diagram > of a tilted plate at high viscosity where the > lifting force is zero: > > http://www.av8n.com//how/img48/barn20x.png > > And here's a diagram of the same plate at low > viscosity, where inertia > effects dominate, and the lift is non-zero: > > http://www.av8n.com//how/img48/barn20z.png > I meant roughly equivalent mass, I said nothing about equivalent air flow patterns. > > Here's another effect: whenever an airfoil is > creating lift, it starts > separating the upper and lower parcels permanently. > Check out the blue > band behind the airfoil in the diagram below when it > is tilted to produce > zero, medium, and high lift: > > http://www.av8n.com//how/img48/3v.png > > "Phase lag" between upper and lower parcels is > proportional to lift. > > > > > The thickest part of the wing lies > > in the front third of it's depth. > > Explanations of lift must be able to handle flat > plates, and symmetrical > thick airfoils, as well as cambered airfoils both > thin and thick. If you > start out by visualizing a thick cambered airfoil, > you're going to run > into trouble. Instead, start out by visualizing a > tilted thin plate (with > no nonlinear flow detachment, of course.) Once you > can explain the tilted > flat thin wing, then you can easily explain the > un-tilted cambered thin > wing... and both these explanations remain the same > for thick streamlined > wings. > OK, I was simplifying a typical airfoil section. The pressure dfferential explanation (which we both promote) still explains all lift. > > > As far as wingtip vortices go, I have some > > counterexamples for you. > > Airplane engineers have often over the years > sought to > > reduce or even eliminate the vortices coming off > the > > wingtips of a jet, many methods of this were > > accomplished, without reducing the wings lift. > > No, they only redistribute the flow pattern without > affecting the total > "vorticity." Because kinetic energy varies as the > square of velocity, a > flow pattern with high velocity near the "vortex > core" will have greater > net KE than a flow pattern that's distributed > differently. > > > Also, many military planes mount missiles on the > very > > tip of the wing, which would dramatically change > the > > flight capability of a plane if the vortices were > the > > primary source of lift. > > The total flow pattern, the "vorticity," is the > primary source of lift. > > Thinking in terms of the "rotating disk balloons" > analogy at this site: > http://amasci.com/wing/rotbal.html , the overall > rotary motion of the > entire "balloons" is what's important, while any > swirling of a central > core of air is unimportant (and wastes energy.) A > wing must produce a > downward-moving pair of rotating cylinders made of > air. Whether the very > center of the cylinders is spinning fast or slow is > irrelevant. It's the > downward acceleration of oncoming still air which > produces lift. > > Perhaps confusion arises because the word "vortex" > can mean "vortex core," > (where "vortex" applies only to the high speed > spinning air near the > center of the flow pattern,) **OR** the word can > apply to the entire > aircraft wake (the entire "rotating balloons" > animated in my article > above.) > > So by adding small winglets to the wing tips, we can > eliminate > the "vortex" (meaning the vortex core only,) while > having no effect on > the "vortex" (meaning the net rotation of the > overall flow pattern.) > Ah, see here is where you had me confused, because typically a "wingtip vortex" is considered to be the vortex "core". > > (( ( ( ( ((O)) ) ) ) > ))) > William J. BeatySCIENCE > HOBBYIST website > billb at amasci com > http://amasci.com > === message truncated === BTW Bill, don't they test wing cross sections in wind tunnels with wings that extend from wall to wall, preventing the formation of the larger vortex wake pattern? Also, it would be interesting actually look at a conservation of momentum study for level flight, because there should be NO net vertical movement of air. The lift on the plane is (wholly or partially) caused by the air which t
Re: OT: Secrets of bee flight revealed
Viktor Schauberger might agree with you. You might also consider Mr. Grimer's Beta-atm list on Yahoo. [EMAIL PROTECTED] "Inside out. Outside in. Perpetual change." BTW, it *was* the lattice ions. -Original Message- From: Rick Monteverde Yeah, that's what I was trying to say, more or less, while answering that notion that the air travels further & faster over the top, etc. *causing* the differential. I don't agree with that version. ___ Try the New Netscape Mail Today! Virtually Spam-Free | More Storage | Import Your Contact List http://mail.netscape.com
RE: OT: Secrets of bee flight revealed
Bill - >There are no forces on the surface of a wing EXCEPT >those of air pressure. > >If you disagree... then you need to explain in detail >what these non-air-pressure forces are. > >But I already know the answer. It's simple: Pressure >differentials explain 100% of the lifting force, while >flow-deflection (the acceleration of fluid masses) also >explains 100% of the lifting force. These are simply >two independant ways of attacking the problem. Yeah, that's what I was trying to say, more or less, while answering that notion that the air travels further & faster over the top, etc. *causing* the differential. I don't agree with that version. >But the incoming air will fill the vacuum chamber, with >the wave travelling at roughly the speed of sound! >In human time scale, as soon as you open the valve >and generate an air jet, significant air pressure >appears on the OTHER side of the wing. You can't >just claim that the pressure there is insignificant, >instead you have to measure it, millisecond by millisecond. The pump is large compared to the small jar volume, and once that dense air in the jet disperses, which it does very quickly, density and pressure get pretty low pretty fast before much of it swirls around underneath the foil. To see it and its scale is convincing. Seeing my writing about it isn't. >If you can show that air can PULL on a curved wing >(i.e. create an absolute negative pressure,) >that's something very interesting. Yup. It's been shown too, but not by me. Google should bring it up with words like van der Waals, airfoil, boundary layer, etc. Why else would a flow stick against a surface and follow it down around a curve like that? I never finished construction on it, but I started a rig where the airfoil sat on a membrane with good vacuum under the membrane in a separate chamnber from the air above the foil. Air jet would hit the top of the foil as before, but the whole bottom side would be against the membrane. Pump would keep the air above at as low a pressure as possible while the jet shot across the foil surface. I figure the foil would still rise into the airflow, pulling up on the membrane with the certain-to-be-lower pressure below it. Maybe simpler to use a split chamber with water instead of air? - Rick
RE: OT: Secrets of bee flight revealed
Harry - I did the vacuum experiment years ago so details are a little hazy, but basically it was a jar with a small diameter (1/8" I.D. I think)tube sticking through the lid. Inside the jar was a small airfoil section made of modelling clay, suspended vertically with the tube pointing at the front/top surface. Basically like the spoon/faucet setup, but with an air jet instead of a faucet. Vacuum pump is high capacity relative to the small air inlet capacity, so when allowing air to flow in through the tube, the vacuum still stays fairly high - so all the significant air action is just the flow hitting the top side of the foil. The foil pulls into the airflow, just like the spoon in a water flow. And I'm pretty sure, mitigated by the absence of any real measurement, that the pressure on the top of the foil was mostly higher than on the bottom. - Rick -Original Message- From: Harry Veeder [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 06, 2005 5:43 PM To: vortex-l@eskimo.com Subject: Re: OT: Secrets of bee flight revealed Rick Monteverde wrote: > Harry - > > I think the wedge effect is the bulk of a real wing's lift. Concurrent > with running a wedge through material, you get pressure differential. > But the cause of the differential is not from faster flow above than > below the curve, etc., it's just a wedge piling up compressible > material on its underside. Contributing also is reaction mass as I've > described, but I can't guess the proportion, and it no doubt varies > with reynolds number - but I think its usually significant. Lastly is > viscous drag on the reaction mass heading downward. I suspect that's > the smallest component on steady-state wings and may be costly in > terms of power spent, but comprises a large lift component in cyclic > wings. OIW "lift" is a composite from several sources in different > proportions depending on wing shape, angle of attack, Reynolds number, > etc. > > Agreed? > Almost I did the spoon-under-the-faucet experiment and it is very persuasive. However, could you please describe your apparatus with the vacuum pump in more detail. I am not intending to replicate the experiment, but I would like to know how you detected a lifting force. Thanks, Harry
Re: OT: Secrets of bee flight revealed
William Beaty wrote: > On Tue, 6 Dec 2005, Rick Monteverde wrote: > >> I don't believe the pressure differential is the full source of lift, > > There are no forces on the surface of a wing EXCEPT those of air pressure. > > If you disagree... then you need to explain in detail what these > non-air-pressure forces are. > > But I already know the answer. It's simple: Pressure differentials > explain 100% of the lifting force, while flow-deflection (the acceleration > of fluid masses) also explains 100% of the lifting force. These are > simply two independant ways of attacking the problem. There is no > competition between a "Bernoulli" viewpoint and a "Newton" viewpoint. > This is just another way of saying that the Bernoulli equation ends up > obeying Newton's laws. Or in other words, if the water is deflected, > there MUST be a pressure differential which causes a lifting force... and > if there is a lifting force, then the water MUST be deflected. I don't think the two explanations are equivalent. During level flight the Bernoulli explanation DOES NOT predict that the fluid leaving the wing tip will be directed downwards. Harry
Re: OT: Secrets of bee flight revealed
At 08:16 pm 06/12/2005 -0800, Bill Beaty wrote: >On Tue, 6 Dec 2005, Harry Veeder wrote: > >> Almost I did the spoon-under-the-faucet >> experiment and it is very persuasive. > Watch out though, since water can support > significant negative pressures. > Or in other words, water in vacuum does > not cavitate unless seed-bubbles are > present, or unless you can produce a > negative pressure. > If you have a piston in a water-filled > cylinder, and you put the whole thing > in a good vacuum, you can pull on the > piston and it will not move. You have > to pull hard before the water cavitates > and "breaks open" to allow the piston > to move. I've seen this effect in > little glass tubes containing water > and hard vacuum. You can create a > tall water column in the upper part > of a tube which is supported only by > attraction to itself and to the glass, > with hard vacuum below. Give the column > a whack, and a tiny bubble appears and > expands, and the column below the bubble > falls rapidly down the tube (and goes > "clank" when it meets another water column > in the bottom of the vertical tube!) > Water really can attract. As good an explanation of reduced Beta-atmosphere pressure as one could wish for - from an arbitrary external data pressure of zero, that is.8-) (cf. 0 degrees C.) Frank Grimer
Re: OT: Secrets of bee flight revealed
On Wed, 7 Dec 2005, Harry Veeder wrote: > Ok. Is it named after Mr. or Ms. Coanda? Henri M. Coanda, here's my favorite links: http://www.allstar.fiu.edu/aero/coanda.htm http://en.wikipedia.org/wiki/Coanda http://jef.raskincenter.org/published/coanda_effect.html http://home.dmv.com/~tbastian/russ.htm There was also an old article in SciAm, where they had a disk-shape styrofoam UFO coanda craft where the air came from the center top, shot horizontally radially outward along the humped disk surface, then blew downwards all around the edge. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
On Wed, 7 Dec 2005, Harry Veeder wrote: > So by "water can support significant negative pressures" you mean the water > can be subjected to significant tensile forces. It's a liquid, so there aren't any directional tension-forces like there would be in, say, a steel cable supporting a weight. It's genuinely negative pressure, and like any pressure, the force is perpendicular to whatever surface happens to be present. For example, if a water column in a vacuum chamber is under negative pressure, and you introduce a tiny vacuum pocket into the water, the pocket will expand rapidly even though the pressure inside such a "bubble" is zero. > > If you have a piston in a water-filled cylinder, and you put the whole > > thing in a good vacuum, you can pull on the piston and it will not move. > > You have to pull hard before the water cavitates and "breaks open" to > > allow the piston to move. I've seen this effect in little glass tubes > > containing water and hard vacuum. You can create a tall water column in > > the upper part of a tube which is supported only by attraction to itself > > and to the glass, with hard vacuum below. Give the column a whack, and a > > tiny bubble appears and expands, and the column below the bubble falls > > rapidly down the tube (and goes "clank" when it meets another water column > > in the bottom of the vertical tube!) Water really can attract. > > > > If the water cavitates in a vacuum I guess that means it is boiling. No, since the same thing happens with any liquid, and the bubbles aren't being inflated by gas pressure. > > Anyway, how is all this related to the spoon experiment in my kichten sink? I think that cohesion forces are major cause of the bent stream. I note that the Coanda effect occurs with air, even though air can't support cohesion-type forces. A clearer demonstration of pure Coanda effect would require that the spoon be immersed underwater, and then a water jet would be directed across the spoon's curved outer surface. When performed with water in air, the negative pressure causes confusion. I know of one professional physicist who doesn't believe in the Coanda effect *because* water jets in air are always used to illustrate it. (It's silly, I know. But when you're arguing with someone hostile who is trying to avoid being proved wrong in public, they will seize on any small flaw in order to "prove" that your explanation is wrong. Using a water stream in air to demonstrate Coanda effect is just such a flaw.) > The faucet was turned on full so the stream flowed with bubbles and on low > so it flowed without bubbles. In both cases I felt the convex side of the > spoon "pulled" into the stream and I could see the stream leaving the tip of > the spoon at an angle. But in air, if the water stream passes close to the spoon without touching, the water stream won't deflect itself to make contact with the spoon. Yet under water, the fluid stream *will* deflect itself to curve around the spoon. Coanda effect involves this deflection, it involves "entrainment," where the moving jet drags any nearby fluid along. In other words, when the spoon is immersed in air, we have to use an air jet to unmistakably demonstrate Coanda effect with no cohesion forces present. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
RC Macaulay wrote: > Hi Harry, > The spoon effect is called the " Coanda effect". Ok. Is it named after Mr. or Ms. Coanda? Harry
Re: OT: Secrets of bee flight revealed
William Beaty wrote: > On Tue, 6 Dec 2005, Harry Veeder wrote: > >> Almost I did the spoon-under-the-faucet experiment and it is very >> persuasive. > > Watch out though, since water can support significant negative pressures. > Or in other words, water in vacuum does not cavitate unless seed-bubbles > are present, or unless you can produce a negative pressure. So by "water can support significant negative pressures" you mean the water can be subjected to significant tensile forces. > If you have a piston in a water-filled cylinder, and you put the whole > thing in a good vacuum, you can pull on the piston and it will not move. > You have to pull hard before the water cavitates and "breaks open" to > allow the piston to move. I've seen this effect in little glass tubes > containing water and hard vacuum. You can create a tall water column in > the upper part of a tube which is supported only by attraction to itself > and to the glass, with hard vacuum below. Give the column a whack, and a > tiny bubble appears and expands, and the column below the bubble falls > rapidly down the tube (and goes "clank" when it meets another water column > in the bottom of the vertical tube!) Water really can attract. > If the water cavitates in a vacuum I guess that means it is boiling. Anyway, how is all this related to the spoon experiment in my kichten sink? The faucet was turned on full so the stream flowed with bubbles and on low so it flowed without bubbles. In both cases I felt the convex side of the spoon "pulled" into the stream and I could see the stream leaving the tip of the spoon at an angle. Harry
Re: OT: Secrets of bee flight revealed
Hi Harry, The spoon effect is called the " Coanda effect". Richard - Original Message - From: "Harry Veeder" <[EMAIL PROTECTED]> To: Sent: Tuesday, December 06, 2005 9:43 PM Subject: Re: OT: Secrets of bee flight revealed Rick Monteverde wrote: Harry - I think the wedge effect is the bulk of a real wing's lift. Concurrent with running a wedge through material, you get pressure differential. But the cause of the differential is not from faster flow above than below the curve, etc., it's just a wedge piling up compressible material on its underside. Contributing also is reaction mass as I've described, but I can't guess the proportion, and it no doubt varies with reynolds number - but I think its usually significant. Lastly is viscous drag on the reaction mass heading downward. I suspect that's the smallest component on steady-state wings and may be costly in terms of power spent, but comprises a large lift component in cyclic wings. OIW "lift" is a composite from several sources in different proportions depending on wing shape, angle of attack, Reynolds number, etc. Agreed? Almost I did the spoon-under-the-faucet experiment and it is very persuasive. However, could you please describe your apparatus with the vacuum pump in more detail. I am not intending to replicate the experiment, but I would like to know how you detected a lifting force. Thanks, Harry
Re: OT: Secrets of bee flight revealed
On Tue, 6 Dec 2005, Harry Veeder wrote: > Almost I did the spoon-under-the-faucet experiment and it is very > persuasive. Watch out though, since water can support significant negative pressures. Or in other words, water in vacuum does not cavitate unless seed-bubbles are present, or unless you can produce a negative pressure. If you have a piston in a water-filled cylinder, and you put the whole thing in a good vacuum, you can pull on the piston and it will not move. You have to pull hard before the water cavitates and "breaks open" to allow the piston to move. I've seen this effect in little glass tubes containing water and hard vacuum. You can create a tall water column in the upper part of a tube which is supported only by attraction to itself and to the glass, with hard vacuum below. Give the column a whack, and a tiny bubble appears and expands, and the column below the bubble falls rapidly down the tube (and goes "clank" when it meets another water column in the bottom of the vertical tube!) Water really can attract. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
RE: OT: Secrets of bee flight revealed
On Tue, 6 Dec 2005, Rick Monteverde wrote: > I think the wedge effect is the bulk of a real wing's lift. The wedge effect is the bulk of a supersonic wing's lift. Don't forget that subsonic fluid dynamics applies to underwater airfoils too. There aren't two different explanations for airfoils in air and in water. Propellors have the same explanation whether they're in air or water... and so do wings. Wings underwater will experience large pressure patterns, yet the density of the incompressible fluid stays the same. Wings in air experience large pressure patterns, yet again, the gas is assumed to be incompressible, and the density changes are assumed to be insignificant (and they aren't part of low-speed aerodynamics math.) > Concurrent > with running a wedge through material, you get pressure differential. > But the cause of the differential is not from faster flow above than > below the curve, etc., it's just a wedge piling up compressible material > on its underside. An underwater wedge doesn't pile up any compressible material. Yet an underwater wedge, if tilted, would still produce lift if the stall effects didn't simply create a turbulent mess. > OIW "lift" > is a composite from several sources in different proportions depending > on wing shape, angle of attack, Reynolds number, etc. > > Agreed? Nope. 100% of the lift comes from Bernoulli and pressure patterns in the fluid of constant density. And 100% of the lift comes from Newton and deflections of moving mass. Only when a wing approaches the speed of sound in fluid, does the normal explanation break down, and acoustic pressure waves start providing significant lift. As I understand it, a supersonic wing is lifted by the high-pressure part of a sound wave, like a strange form of radiation pressure. The wing is still grabbing air and flinging it, and experincing pressure patterns and reaction forces, but we end up with the physics of standing wave acoustics rather than the physics of wind. (I've only seen one textbook which goes into the details of supersonic lifting force.) (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
RE: OT: Secrets of bee flight revealed
On Tue, 6 Dec 2005, Rick Monteverde wrote: > I don't believe the pressure differential is the full source of lift, There are no forces on the surface of a wing EXCEPT those of air pressure. If you disagree... then you need to explain in detail what these non-air-pressure forces are. But I already know the answer. It's simple: Pressure differentials explain 100% of the lifting force, while flow-deflection (the acceleration of fluid masses) also explains 100% of the lifting force. These are simply two independant ways of attacking the problem. There is no competition between a "Bernoulli" viewpoint and a "Newton" viewpoint. This is just another way of saying that the Bernoulli equation ends up obeying Newton's laws. Or in other words, if the water is deflected, there MUST be a pressure differential which causes a lifting force... and if there is a lifting force, then the water MUST be deflected. > I've tried this in a vacuum jar running a strong/fast pump to hold a > good vacuum, then using a small jet of air over a wing-shaped object. > Still works - the curved piece experiences a force into the stream. > Although I did not measure pressure top and bottom on the small wing > piece, the pressure in the jar was very low, and the stream coming out > of the tube was basically at room pressure. Again, the cool part of this > is that the stream adheres to the upper surface even as the surface > curves away from the straight line, apparently due to the same forces > that hold gekkos to walls. Airplanes are ZPE machines, sort of. But the incoming air will fill the vacuum chamber, with the wave travelling at roughly the speed of sound! In human time scale, as soon as you open the valve and generate an air jet, significant air pressure appears on the OTHER side of the wing. You can't just claim that the pressure there is insignificant, instead you have to measure it, millisecond by millisecond. If you can show that air can PULL on a curved wing (i.e. create an absolute negative pressure,) that's something very interesting. PS, I see I have to modify my original statement: ALL FLIGHT IN FLUIDS OF NEARLY CONSTANT DENSITY... IS CAUSED BY VORTEX-SHEDDING. I forgot about supersonic flight. In supersonic flight the lifting force involves major density changes, and there are no vortices, since a vortex can only set itself up by propagating a flow pattern at less than the speed of sound. Vortex-shedding applies to bird flight, insects, fish, boats, etc. Vortex-shedding doesn't apply after the shockwaves take over. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
Rick Monteverde wrote: > Harry - > > I think the wedge effect is the bulk of a real wing's lift. Concurrent > with running a wedge through material, you get pressure differential. > But the cause of the differential is not from faster flow above than > below the curve, etc., it's just a wedge piling up compressible material > on its underside. Contributing also is reaction mass as I've described, > but I can't guess the proportion, and it no doubt varies with reynolds > number - but I think its usually significant. Lastly is viscous drag on > the reaction mass heading downward. I suspect that's the smallest > component on steady-state wings and may be costly in terms of power > spent, but comprises a large lift component in cyclic wings. OIW "lift" > is a composite from several sources in different proportions depending > on wing shape, angle of attack, Reynolds number, etc. > > Agreed? > Almost I did the spoon-under-the-faucet experiment and it is very persuasive. However, could you please describe your apparatus with the vacuum pump in more detail. I am not intending to replicate the experiment, but I would like to know how you detected a lifting force. Thanks, Harry
Re: OT: Secrets of bee flight revealed
On Tue, 6 Dec 2005, Merlyn wrote: > I don't agree with Bernoulli, but pressure is still > the key. First see: http://amasci.com/wing/airfoil.html, and especially the FAQ at http://amasci.com/wing/airfoil.html#faq > As the wing pushes through the air, the leading edge > divides the air into roughly equivalent parts flowing > above and below. Nope, doesn't happen. When the pattern of air flowing above and below the wing are the same, then the lift is zero. For example, here's a diagram of a tilted plate at high viscosity where the lifting force is zero: http://www.av8n.com//how/img48/barn20x.png And here's a diagram of the same plate at low viscosity, where inertia effects dominate, and the lift is non-zero: http://www.av8n.com//how/img48/barn20z.png Pay close attention to the trailing edge of the tilted plates in both diagrams. When high viscosity damps out the inertia effects and prevents lift (upper GIF), it damps the chordwise circulatory motion, and the flow patterns become symmetrical above and below. The flow at the leading edge is about the same as the flow near the trailing edge. And at the same time, the air leaving the trailing edge will make a tight turn, changing direction. But when viscosity is low, and lift is significant, and the "circulation" appears, inertia causes the air to flow smoothly off the trailing edge. The flow near the leading edge becomes very different than the flow near the trailing edge. At the same time, the flow patterns above and below the wing become very different, and air above the wing flows much faster. Those diagrams are from http://www.av8n.com//how/htm/airfoils.html Here's another effect: whenever an airfoil is creating lift, it starts separating the upper and lower parcels permanently. Check out the blue band behind the airfoil in the diagram below when it is tilted to produce zero, medium, and high lift: http://www.av8n.com//how/img48/3v.png "Phase lag" between upper and lower parcels is proportional to lift. > The thickest part of the wing lies > in the front third of it's depth. Explanations of lift must be able to handle flat plates, and symmetrical thick airfoils, as well as cambered airfoils both thin and thick. If you start out by visualizing a thick cambered airfoil, you're going to run into trouble. Instead, start out by visualizing a tilted thin plate (with no nonlinear flow detachment, of course.) Once you can explain the tilted flat thin wing, then you can easily explain the un-tilted cambered thin wing... and both these explanations remain the same for thick streamlined wings. > As far as wingtip vortices go, I have some > counterexamples for you. > Airplane engineers have often over the years sought to > reduce or even eliminate the vortices coming off the > wingtips of a jet, many methods of this were > accomplished, without reducing the wings lift. No, they only redistribute the flow pattern without affecting the total "vorticity." Because kinetic energy varies as the square of velocity, a flow pattern with high velocity near the "vortex core" will have greater net KE than a flow pattern that's distributed differently. > Also, many military planes mount missiles on the very > tip of the wing, which would dramatically change the > flight capability of a plane if the vortices were the > primary source of lift. The total flow pattern, the "vorticity," is the primary source of lift. Thinking in terms of the "rotating disk balloons" analogy at this site: http://amasci.com/wing/rotbal.html , the overall rotary motion of the entire "balloons" is what's important, while any swirling of a central core of air is unimportant (and wastes energy.) A wing must produce a downward-moving pair of rotating cylinders made of air. Whether the very center of the cylinders is spinning fast or slow is irrelevant. It's the downward acceleration of oncoming still air which produces lift. Perhaps confusion arises because the word "vortex" can mean "vortex core," (where "vortex" applies only to the high speed spinning air near the center of the flow pattern,) **OR** the word can apply to the entire aircraft wake (the entire "rotating balloons" animated in my article above.) So by adding small winglets to the wing tips, we can eliminate the "vortex" (meaning the vortex core only,) while having no effect on the "vortex" (meaning the net rotation of the overall flow pattern.) PS, the math of fluid flow is the same as the math for magnetic fields surrounding a set of wires. In fluid flow, a "vortex" is the entire circular magnetic field surrounding an infinite straight wire, and the "vorticity" of the overall flow is determined by the current in the wire. By placing clumps of iron around the wire, we can sculpt the field pattern, yet this has no effect on the overall swirling of the field: the "vorticity." To use current-carrying wires to produce a wing's flow pattern, we just run a pair of parallel wires backwards off the
RE: OT: Secrets of bee flight revealed
Harry - I think the wedge effect is the bulk of a real wing's lift. Concurrent with running a wedge through material, you get pressure differential. But the cause of the differential is not from faster flow above than below the curve, etc., it's just a wedge piling up compressible material on its underside. Contributing also is reaction mass as I've described, but I can't guess the proportion, and it no doubt varies with reynolds number - but I think its usually significant. Lastly is viscous drag on the reaction mass heading downward. I suspect that's the smallest component on steady-state wings and may be costly in terms of power spent, but comprises a large lift component in cyclic wings. OIW "lift" is a composite from several sources in different proportions depending on wing shape, angle of attack, Reynolds number, etc. Agreed? >I think a pressure differential is the primary source >of the lift, because your experiment does not result >in the full weight of the wing being lifted. > >Harry
Re: OT: Secrets of bee flight revealed
Rick Monteverde wrote: > I don't believe the pressure differential is the full source of lift, > though I don't doubt a differential exists. I've seen it work > differently first hand. > > Hang a spoon against the flow of water from a faucet, bottom side > against the flow. No magic, just water sticking to the spoon due to > mysterious forces between objects (ok, little bit of magic). The water > flows along the curve of the spoon, then gets hurled off at a slight > angle, shedding a 'vortex', or at least a curve that might be considered > part of a large partially formed vortex. The hurling at a slight angle > causes the thrust - would be lift if the thing were horizontal instead > of vertical. The water on the other side of the spoon provides no > "pressure" because there isn't any water there. > > I've tried this in a vacuum jar running a strong/fast pump to hold a > good vacuum, then using a small jet of air over a wing-shaped object. > Still works - the curved piece experiences a force into the stream. > Although I did not measure pressure top and bottom on the small wing > piece, the pressure in the jar was very low, and the stream coming out > of the tube was basically at room pressure. Again, the cool part of this > is that the stream adheres to the upper surface even as the surface > curves away from the straight line, apparently due to the same forces > that hold gekkos to walls. Airplanes are ZPE machines, sort of. > I think a pressure differential is the primary source of the lift, because your experiment does not result in the full weight of the wing being lifted. Harry
RE: OT: Secrets of bee flight revealed
I don't believe the pressure differential is the full source of lift, though I don't doubt a differential exists. I've seen it work differently first hand. Hang a spoon against the flow of water from a faucet, bottom side against the flow. No magic, just water sticking to the spoon due to mysterious forces between objects (ok, little bit of magic). The water flows along the curve of the spoon, then gets hurled off at a slight angle, shedding a 'vortex', or at least a curve that might be considered part of a large partially formed vortex. The hurling at a slight angle causes the thrust - would be lift if the thing were horizontal instead of vertical. The water on the other side of the spoon provides no "pressure" because there isn't any water there. I've tried this in a vacuum jar running a strong/fast pump to hold a good vacuum, then using a small jet of air over a wing-shaped object. Still works - the curved piece experiences a force into the stream. Although I did not measure pressure top and bottom on the small wing piece, the pressure in the jar was very low, and the stream coming out of the tube was basically at room pressure. Again, the cool part of this is that the stream adheres to the upper surface even as the surface curves away from the straight line, apparently due to the same forces that hold gekkos to walls. Airplanes are ZPE machines, sort of. I think conventional steady-state wings get lift from a combination of being a wedge, and a mover of reaction mass. Flat surfaced flapping wings - mostly viscous drag and reaction mass, and maybe a little bit wedge at certain parts of their cycle. - Rick -Original Message- From: Merlyn [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 06, 2005 8:47 AM To: vortex-l@eskimo.com Subject: Re: OT: Secrets of bee flight revealed I most humbly (or perhaps not so humbly) beg to differ. --- William Beaty <[EMAIL PROTECTED]> wrote: > In other words... (and in big capital letters,) > >ALL FLIGHT IS BASED ON VORTEX-SHEDDING > > Corellary: if your explanation of flight does not > include vortex-shedding, > then it is wrong. > I don't agree with Bernoulli, but pressure is still the key. As the wing pushes through the air, the leading edge divides the air into roughly equivalent parts flowing above and below. The thickest part of the wing lies in the front third of it's depth. After this point, the top of the wing drops, while the bottom remains effectively flat. This produces an area above the wing of lower pressure which lifts the wing. The area below the wing has a slightly higher pressure, and when this spills up around the wingtip it creates the vortex. As far as wingtip vortices go, I have some counterexamples for you. Airplane engineers have often over the years sought to reduce or even eliminate the vortices coming off the wingtips of a jet, many methods of this were accomplished, without reducing the wings lift. http://www.fas.org/nuke/guide/usa/airdef/f-94.htm http://www.fas.org/man/dod-101/sys/ac/c-20.htm Also, many military planes mount missiles on the very tip of the wing, which would dramatically change the flight capability of a plane if the vortices were the primary source of lift. http://www.fas.org/man/dod-101/sys/ac/f-16.htm Merlyn Magickal Engineer and Technical Metaphysicist __ Yahoo! DSL - Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com
Re: OT: Secrets of bee flight revealed
This is a great discussion. Who can fail to wonder about the principles of flight? Bernoulli's principle is almost magical. It says the same air mass which separates at the leading edge of the wing reunites at the trailing edge. Due to the shape of a wing this requires that the air mass moving over the top must travel a greater distance in the same period of time as the air mass at the bottom of the wing. The question is how does the top air mass manage to speed up and then slow down again so it reunites with the bottom air mass at just the right time. How does the air manage to move in such a co-ordinated fashion? Here is another explanation. First consider a flat plate in free fall. As the plate falls it creates a region of low pressure above the plate: a sort of suction effect. This slows the descent of the plate. What then is the function of the classic airfoil cross section? The shape increases the suction power enough on the wing so that it can stay aloft and travel in level flight. Harry Merlyn wrote: > I most humbly (or perhaps not so humbly) beg to > differ. > > --- William Beaty <[EMAIL PROTECTED]> wrote: > >> In other words... (and in big capital letters,) >> >> ALL FLIGHT IS BASED ON VORTEX-SHEDDING >> >> Corellary: if your explanation of flight does not >> include vortex-shedding, >> then it is wrong. >> > > > I don't agree with Bernoulli, but pressure is still > the key. > As the wing pushes through the air, the leading edge > divides the air into roughly equivalent parts flowing > above and below. The thickest part of the wing lies > in the front third of it's depth. After this point, > the top of the wing drops, while the bottom remains > effectively flat. This produces an area above the > wing of lower pressure which lifts the wing. The area > below the wing has a slightly higher pressure, and > when this spills up around the wingtip it creates the > vortex. > > As far as wingtip vortices go, I have some > counterexamples for you. > Airplane engineers have often over the years sought to > reduce or even eliminate the vortices coming off the > wingtips of a jet, many methods of this were > accomplished, without reducing the wings lift. > http://www.fas.org/nuke/guide/usa/airdef/f-94.htm > http://www.fas.org/man/dod-101/sys/ac/c-20.htm > > Also, many military planes mount missiles on the very > tip of the wing, which would dramatically change the > flight capability of a plane if the vortices were the > primary source of lift. > http://www.fas.org/man/dod-101/sys/ac/f-16.htm > > Merlyn > Magickal Engineer and Technical Metaphysicist > > > > __ > Yahoo! DSL Something to write home about. > Just $16.99/mo. or less. > dsl.yahoo.com >
Re: OT: Secrets of bee flight revealed
I most humbly (or perhaps not so humbly) beg to differ. --- William Beaty <[EMAIL PROTECTED]> wrote: > In other words... (and in big capital letters,) > >ALL FLIGHT IS BASED ON VORTEX-SHEDDING > > Corellary: if your explanation of flight does not > include vortex-shedding, > then it is wrong. > I don't agree with Bernoulli, but pressure is still the key. As the wing pushes through the air, the leading edge divides the air into roughly equivalent parts flowing above and below. The thickest part of the wing lies in the front third of it's depth. After this point, the top of the wing drops, while the bottom remains effectively flat. This produces an area above the wing of lower pressure which lifts the wing. The area below the wing has a slightly higher pressure, and when this spills up around the wingtip it creates the vortex. As far as wingtip vortices go, I have some counterexamples for you. Airplane engineers have often over the years sought to reduce or even eliminate the vortices coming off the wingtips of a jet, many methods of this were accomplished, without reducing the wings lift. http://www.fas.org/nuke/guide/usa/airdef/f-94.htm http://www.fas.org/man/dod-101/sys/ac/c-20.htm Also, many military planes mount missiles on the very tip of the wing, which would dramatically change the flight capability of a plane if the vortices were the primary source of lift. http://www.fas.org/man/dod-101/sys/ac/f-16.htm Merlyn Magickal Engineer and Technical Metaphysicist __ Yahoo! DSL Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com
Re: OT: Secrets of bee flight revealed
Hi Norman,
Neat observations you have. As one may surmise, an
entire host of unknowns stand waiting understanding in the advancement of
science. Perhaps the greatest obstacle to date has been the limited capacity of
human minds to grasp the magnitude of the wonders of creation.
The primary function of the butterfly wing may be far
removed from a propulsion device. The massive size of the wing ( as measured
against a bee wing) is an apparent contradiction. The large wing may be used
mostly for stabilizing. Surely the patternation serves multiple purposes other
than mating. After all, "colors" are "music" in another realm of understanding.
As the poet stated.. oh ,what fools we mortals be.. add blind
to that thought .
Richard
- Original Message -
From:
NORMAN HORWOOD
To: vortex-l@eskimo.com
Sent: Monday, December 05, 2005 6:08
AM
Subject: Re: OT: Secrets of bee flight
revealed
Sticking my lurker's head above the
parapet may I comment on the flight of the butterfly.
This has always fascinated me, and
Richard's observations have triggered some hopefully useful
thoughts.
What if the wings are the sensors of
IR from the various vortices in the air movement as well as small variations
in the local velocity dynamics? Might it also be within the realms of
possibility that the patternation of the wing serves more than mating
attraction, but also an electro-cellular function. Their wing
action is very stop and go which might be useful for direction-finding while
the wings are stationary in flight.
Having watched the recent
BBC series by Richard Attenborough on "Life in the undergrowth"; the
extraordinary capabilities of the minutest life-forms with almost zero brain
volume stirs the imagination to extreme limits.
Norman Horwood Berkshire
UK
- Original Message -
From:
RC Macaulay
To: vortex-l@eskimo.com
Sent: Monday, December 05, 2005 4:27
AM
Subject: Re: OT: Secrets of bee flight
revealed
The flight of the butterfly is every bit as interesting as the bee.
They appear to " flutter" from flower to flower. Watching closely, they
appear to be directionless in flight, yet wind up where they are going. As
they flutter in an seeming aimless way, they can change their speed and
direction at an amazing rate.
In our research studies in liquid vortex I have mentioned the formation
of vortices shed off the main "rope". These vortices are short lived yet
traverse the width and depth of the glass test tank. Some are vertical,
diagonal and horizontal. They can be tracked using a thermister sensor since
they produce a heat source.
I have often watched the grassland pasture at our ranch. The wind
undulates the grass in waves. This undulation is caused by horizontal wind
vortexes. Butterflys can fly in these winds and reach flowers as they
select. How can this be possible when the body weight and wing area doesn't
make sense for flight, much less guidance? The answer may be found
in some of Schauberger's papers that describe how a fish can climb a
waterfall. The fish finds the reverse vortex inside the "rope" and is
partially " catapulted up the "rope".
This would explain the butterfly's ability to fly against a wind
and end up at the next flower. It would explain why the butterfly's
speed and direction can change instantly. The butterfly could have
sensors that detect the random wind vortexes and uses the vortex energy and
position for direction and movement like the fish in waterfall. Pity we
can't "see" wind vortexes, perhaps all birds can.
Richard
Re: OT: Secrets of bee flight revealed
Sticking my lurker's head above the parapet may I comment on the flight of the butterfly. This has always fascinated me, and Richard's observations have triggered some hopefully useful thoughts. What if the wings are the sensors of IR from the various vortices in the air movement as well as small variations in the local velocity dynamics? Might it also be within the realms of possibility that the patternation of the wing serves more than mating attraction, but also an electro-cellular function. Their wing action is very stop and go which might be useful for direction-finding while the wings are stationary in flight. Having watched the recent BBC series by Richard Attenborough on "Life in the undergrowth"; the extraordinary capabilities of the minutest life-forms with almost zero brain volume stirs the imagination to extreme limits. Norman Horwood Berkshire UK - Original Message - From: RC Macaulay To: vortex-l@eskimo.com Sent: Monday, December 05, 2005 4:27 AM Subject: Re: OT: Secrets of bee flight revealed The flight of the butterfly is every bit as interesting as the bee. They appear to " flutter" from flower to flower. Watching closely, they appear to be directionless in flight, yet wind up where they are going. As they flutter in an seeming aimless way, they can change their speed and direction at an amazing rate. In our research studies in liquid vortex I have mentioned the formation of vortices shed off the main "rope". These vortices are short lived yet traverse the width and depth of the glass test tank. Some are vertical, diagonal and horizontal. They can be tracked using a thermister sensor since they produce a heat source. I have often watched the grassland pasture at our ranch. The wind undulates the grass in waves. This undulation is caused by horizontal wind vortexes. Butterflys can fly in these winds and reach flowers as they select. How can this be possible when the body weight and wing area doesn't make sense for flight, much less guidance? The answer may be found in some of Schauberger's papers that describe how a fish can climb a waterfall. The fish finds the reverse vortex inside the "rope" and is partially " catapulted up the "rope". This would explain the butterfly's ability to fly against a wind and end up at the next flower. It would explain why the butterfly's speed and direction can change instantly. The butterfly could have sensors that detect the random wind vortexes and uses the vortex energy and position for direction and movement like the fish in waterfall. Pity we can't "see" wind vortexes, perhaps all birds can. Richard
Re: OT: Secrets of bee flight revealed
William Beaty wrote: > On Wed, 30 Nov 2005, Harry Veeder wrote: > >> If you really look at it closely it sounds like a mathematical trick which >> makes the mathematical predictions consistent with experiment. > > No, it's based on the fact that if you trace the flows of a moving vortex > ring, you'll find that the ring carries a sphere-shape of fluid along with > it as it travels. The surface of this sphere, the "separatrix," pushes > water around itself as it moves forward (just as a solid sphere would do.) Ok. > So if a paddle DOESN'T create a ring-vortex, then it's added mass will be > extremely low. And if a paddle sheds the vortex that it has created, well > that's the same as launching an actual physical very genuine ball of > water. Yes and the bigger the vortices the greater the effort by the paddler. >> In newtonian mechanics you can't add mass to a system unless it is done by >> adding a force first. > > If you're underwater and you fill a plastic garbage bag with water, then > the effective mass of the garbage bag has increased by hundreds of pounds! > > Compare it to the effective mass of a flattened and folded-up garbage bag. > The "added" mass comes from the environment. If we attach some of the > surrounding water or air to a moving paddle, then the paddle will "become" > massive, and it will accelerate that parcel of fluid if the paddle moves. The point is you begin your analysis of the forces on a given body in a fluid, whether the body is an empty plastic bag or a bag full of water or a paddle, the added-mass is a consequence of the acceleration of the body through the fluid. What puzzles me is how one goes about calculating how much fluid mass to add to the paddle's. One can learn this empirically or with physical models but theoretically it seems more like a matter of informed guesswork to me. > In other words... (and in big capital letters,) > > ALL FLIGHT IS BASED ON VORTEX-SHEDDING > > Corellary: if your explanation of flight does not include vortex-shedding, > then it is wrong. May we say all flight begins with added-mass and is followed by the added-mass being shed as a vortex? Harry
Re: OT: Secrets of bee flight revealed
The flight of the butterfly is every bit as interesting as the bee. They appear to " flutter" from flower to flower. Watching closely, they appear to be directionless in flight, yet wind up where they are going. As they flutter in an seeming aimless way, they can change their speed and direction at an amazing rate. In our research studies in liquid vortex I have mentioned the formation of vortices shed off the main "rope". These vortices are short lived yet traverse the width and depth of the glass test tank. Some are vertical, diagonal and horizontal. They can be tracked using a thermister sensor since they produce a heat source. I have often watched the grassland pasture at our ranch. The wind undulates the grass in waves. This undulation is caused by horizontal wind vortexes. Butterflys can fly in these winds and reach flowers as they select. How can this be possible when the body weight and wing area doesn't make sense for flight, much less guidance? The answer may be found in some of Schauberger's papers that describe how a fish can climb a waterfall. The fish finds the reverse vortex inside the "rope" and is partially " catapulted up the "rope". This would explain the butterfly's ability to fly against a wind and end up at the next flower. It would explain why the butterfly's speed and direction can change instantly. The butterfly could have sensors that detect the random wind vortexes and uses the vortex energy and position for direction and movement like the fish in waterfall. Pity we can't "see" wind vortexes, perhaps all birds can. Richard
Re: OT: Secrets of bee flight revealed
On Wed, 30 Nov 2005, Harry Veeder wrote: > If you really look at it closely it sounds like a mathematical trick which > makes the mathematical predictions consistent with experiment. No, it's based on the fact that if you trace the flows of a moving vortex ring, you'll find that the ring carries a sphere-shape of fluid along with it as it travels. The surface of this sphere, the "separatrix," pushes water around itself as it moves forward (just as a solid sphere would do.) So if a paddle DOESN'T create a ring-vortex, then it's added mass will be extremely low. And if a paddle sheds the vortex that it has created, well that's the same as launching an actual physical very genuine ball of water. > In newtonian mechanics you can't add mass to a system unless it is done by > adding a force first. If you're underwater and you fill a plastic garbage bag with water, then the effective mass of the garbage bag has increased by hundreds of pounds! Compare it to the effective mass of a flattened and folded-up garbage bag. The "added" mass comes from the environment. If we attach some of the surrounding water or air to a moving paddle, then the paddle will "become" massive, and it will accelerate that parcel of fluid if the paddle moves. In other words... (and in big capital letters,) ALL FLIGHT IS BASED ON VORTEX-SHEDDING Corellary: if your explanation of flight does not include vortex-shedding, then it is wrong. (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
On Wed, 30 Nov 2005, Grimer wrote: > At 01:40 pm 30/11/2005 -0500, Harry wrote: > > > BTW, the article mentions "added-mass force". Does anyone > > know what that means? > > "Added mass is the weight added to a system due > to the fact that an accelerating or decelerating > body must move some volume of surrounding fluid > with it as it moves. The added mass force opposes > the motion, and acts as a kind of drag force. It's the basis of flight. It's also how rowboats work: if you push a paddle along, it carries a ring-vortex of water with it, and the paddle seems massive because of this "ball" of water being accelerated. But if you then lift the paddle out (or simply turn it 90degrees so it moves edge-on,) then the paddle DOESN'T carry a huge mass of water with it during the return stroke. In other words, the paddle launches massive balls of water. Fish tails (and bodies) work like this too. Ships' propellors do the same, but on a continuous basis sending out a long cylinder of water. Airplanes do it too, but the "balls" are pairs of long tube-shapes of air. It looks like aerodynamicists are finally getting the hang of thinking in terms of Newtonian mechanics and reaction engines rather than in Paradigm Blindness terms using venturi forces and Bernoulli's equation. But it's only happened in the last ten years or so. Amazing, no? See: Water striders launch underwater vortices http://www.nature.com/nature/journal/v424/n6949/abs/nature01793.html (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
On Wed, 30 Nov 2005, Harry Veeder wrote: > Secrets of bee flight revealed > http://www.newscientist.com/article.ns?id=dn8382 > > Combining robotic modelling with slow-motion videos of airborne honeybees > may have helped researchers explain the curious aerodynamics of bee flight. Perhaps one important point gets lost: Aerodynamicists don't understand how flight works! The math is impenetrable because viscosity and turbulence is an essential component. And worse, most scientists picked up in grade school an incorrect explanation of how wings work. Viscous flow is a nonlinear system, so like the 3-body orbit problem, there are no general solutions. You have to run numerical simulations, and this is mostly impossible because a proper simulation must include effects on the scale of atoms and millimeters and tens of meters. Even simulators using supercompter arrays can only give quite crude results. In other words, the science of Aerodynamics might SEEM to be sophisticated, yet they're still laboring in the dark ages. Flapping-wing insect flight wasn't slightly understood until the 1990s, when someone finally had the brilliant idea of building a pair of big plastic moth wings and running them in a water tank with bubble streams as flow markers. GEEZE! This is supposed to be a professional science, yet the cutting-edge research is stuff that Bill Nye might do. And worse, it took them until the 1990s to think of the technique. (Note that the bee-flight stuff is just a footnote on the famous/infamous Berkeley Hawk Moth flapping wing machine from the mid 1990s.) > Aeronautical engineers had previously ³proven² that bees cannot fly. Nope, this one is an urban legend. Tracing the "bumblebee's can't fly" myth http://www.sciencenews.org/articles/20040911/mathtrek.asp Me, I think the bumblebee legend is a distortion of "we have almost no idea how flapping-wing flight works." In my own amateur research I was stunned when I found that airplanes fly because of vortex-shedding, while the usuall "Bernoulli effect" explanation in textbooks is either wrong, or it only applies to ground-effect flight which exists for a few seconds during takeoff. Here's an animation of a diagram I created. So far I've not found any similar diagram in aerodynamics texts nor on online aerodynamics education sites. I suspect that professional aerodynamicists are missing this simple, grade-school, gut-level explanation, and it warps their understanding. Animation: vortex-shedding momentum effect http://amasci.com/wing/rotbal1.html Also: Solving the mystery of flapping flight http://journals2.iranscience.net:800/www.sciam.com/www.sciam.com/[EMAIL PROTECTED] Wakes in flapping flight http://www.biology.leeds.ac.uk/staff/jmvr/Flight/modelling.htm (( ( ( ( ((O)) ) ) ) ))) William J. BeatySCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775unusual phenomena, tesla coils, weird sci
Re: OT: Secrets of bee flight revealed
Grimer wrote: > At 01:40 pm 30/11/2005 -0500, Harry wrote: > >> This article was brought to my attention on another list. >> I thought it would be of interest to those who followed >> the vortex discussion on humming bird flight earlier this year. >> >> BTW, the article mentions "added-mass force". Does anyone >> know what that means? > > > > "Added mass is the weight added to a system due > to the fact that an accelerating or decelerating > body must move some volume of surrounding fluid > with it as it moves. The added mass force opposes > the motion, and acts as a kind of drag force. > > Not to be confused with relativistic mass increase." > > Ain't Wiki wonderful 8-) > > If you really look at it closely it sounds like a mathematical trick which makes the mathematical predictions consistent with experiment. In newtonian mechanics you can't add mass to a system unless it is done by adding a force first. If there is literally no new mass then it is just an old fashioned drag or a lift force. So either we ( the royal we) really mean NEW mass or we mean old force by a new name. Harry
Re: OT: Secrets of bee flight revealed
At 01:40 pm 30/11/2005 -0500, Harry wrote: > This article was brought to my attention on another list. > I thought it would be of interest to those who followed > the vortex discussion on humming bird flight earlier this year. > > BTW, the article mentions "added-mass force". Does anyone > know what that means? "Added mass is the weight added to a system due to the fact that an accelerating or decelerating body must move some volume of surrounding fluid with it as it moves. The added mass force opposes the motion, and acts as a kind of drag force. Not to be confused with relativistic mass increase." Ain't Wiki wonderful 8-)
