On 11/25/2010 10:08 PM, Rune Allnor wrote:> On Nov 25, 6:32 pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: >> On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor >> >> >> >> >> >> <all...@tele.ntnu.no> wrote: >>> Hi all. >> >>> This is one of those questions that just popped into my mind >>> last night: Who invented / discovered the airfoil? Like in aviation >>> history. >> >>> I know the Montgolfiers discovered the balloon, the Wright did >>> the first powered flight and so on, but who was the first to >>> describe the airforil as a component for 'heavier-than-air' flight? >> >>> Lilienthal used devices very similar to what we today would call >>> hang gliders a couple of decades before the Wrights got their >>> flyer together. I have seen claims that one of Lilienthal's main >>> contributions to aviation history was that he published a very >>> detailed description of the flight charactersitics of the airfoil >>> glider, >>> a description that turned out to be essential for e.g. the Wrights >>> to be able to build an actualair plane. >> >>> But describing the airfoil charactersitics is one thing - who >>> *invented* the airfoil? Was it ol'e Otto himself? Or somebody else? >> >>> Rune >> >> Birds have had them for a long time. Some flying reptiles before >> that. >> >> IIRC DaVinci did a bunch of sketches of bird wings and had various >> illustrated ideas about flying machines. >> >> I don't know if it's an "invention" if you just copy or adapt it off a >> bird. > > Of course. But the question that popped into my head the other > day was who first described the airfoil as a viable method for > human aviation. Leonardo drew / fantasized about the thing, but > did not verify that it actually worked. > > I suppose I'll settle for Lilienthal.I don't think you can settle for anyone, really -- from the link I posted it sounds like there were a number of people responding to the zeitgeist, who were all looking into airfoil theory at the same time. That sort of thing does sometimes coalesce out of thin air. Lilienthal should get credit for his compendium, but I'm not so sure that he should be credited as "the father of the airfoil" or anything. If you truly want to give credit to the invention of current airfoil theory, then look to the multitude of aerodynamic researchers who worked between the world wars, and figured out the essential whys and wherefores of airfoils, and brought the world the standard subsonic airfoil shapes -- many of which are still being used. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
OT: Who invented the airfoil?
Started by ●November 25, 2010
Reply by ●November 26, 20102010-11-26
Reply by ●December 11, 20102010-12-11
On Nov 26, 2:05=A0pm, Tim Wescott <t...@seemywebsite.com> wrote:> On 11/25/2010 10:08 PM, Rune Allnor wrote: > > > > > On Nov 25, 6:32 pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > >> On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > >> <all...@tele.ntnu.no> =A0wrote: > >>> Hi all. > > >>> This is one of those questions that just popped into my mind > >>> last night: Who invented / discovered the airfoil? Like in aviation > >>> history. > > >>> I know the Montgolfiers discovered the balloon, the Wright did > >>> the first powered flight and so on, but who was the first to > >>> describe the airforil as a component for 'heavier-than-air' flight? > > >>> Lilienthal used devices very similar to what we today would call > >>> hang gliders a couple of decades before the Wrights got their > >>> flyer together. I have seen claims that one of Lilienthal's main > >>> contributions to aviation history was that he published a very > >>> detailed description of the flight charactersitics of the airfoil > >>> glider, > >>> a description that turned out to be essential for e.g. the Wrights > >>> to be able to build an actualair plane. > > >>> But describing the airfoil charactersitics is one thing - who > >>> *invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > >>> Rune > > >> Birds have had them for a long time. =A0 Some flying reptiles before > >> that. > > >> IIRC DaVinci did a bunch of sketches of bird wings and had various > >> illustrated ideas about flying machines. > > >> I don't know if it's an "invention" if you just copy or adapt it off a > >> bird. > > > Of course. But the question that popped into my head the other > > day was who first described the airfoil as a viable method for > > human aviation. Leonardo drew / fantasized about the thing, but > > did not verify that it actually worked. > > > I suppose I'll settle for Lilienthal. > > I don't think you can settle for anyone, really -- from the link I > posted it sounds like there were a number of people responding to the > zeitgeist, who were all looking into airfoil theory at the same time. > That sort of thing does sometimes coalesce out of thin air. =A0Lilienthal > should get credit for his compendium, but I'm not so sure that he should > be credited as "the father of the airfoil" or anything. > > If you truly want to give credit to the invention of current airfoil > theory, then look to the multitude of aerodynamic researchers who worked > between the world wars, and figured out the essential whys and > wherefores of airfoils, and brought the world the standard subsonic > airfoil shapes -- many of which are still being used. > > -- > > Tim Wescott > Wescott Design Serviceshttp://www.wescottdesign.com > > Do you need to implement control loops in software? > "Applied Control Theory for Embedded Systems" was written for you. > See details athttp://www.wescottdesign.com/actfes/actfes.htmlA lot of "airfoil" development was done on blade shapes for turbines. Even Pelton wheels has shaped buckets that are much more efficient than simple vanes. The work of a turbine blade, boat sail, or airplane wing is changing the direction (and perhaps speed) of the fluid flowing past it. Doing that with minimum loss dictates that the leading edge face directly into the impinging flow and that the trailing edge be parallel to the departing flow. Clearly, that implies a curved surface. For high-velocity flow, the usual teardrop streamline shape reduces drag. Add that to the necessary curve, and the classic airfoil shape is the result. At low speeds, the extra weight of a thick wing is an impediment. The ROG models I built as a kid all had wing covering only on the upper side. Oh: ROG stands for "rise off ground". These were rubber-powered planes released on pavement or bare ground. Jerry
Reply by ●December 12, 20102010-12-12
>On Nov 26, 2:05=A0pm, Tim Wescott <t...@seemywebsite.com> wrote: >> On 11/25/2010 10:08 PM, Rune Allnor wrote: >> >> >> >> > On Nov 25, 6:32 pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: >> >> On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor >> >> >> <all...@tele.ntnu.no> =A0wrote: >> >>> Hi all. >> >> >>> This is one of those questions that just popped into my mind >> >>> last night: Who invented / discovered the airfoil? Like in aviation >> >>> history. >> >> >>> I know the Montgolfiers discovered the balloon, the Wright did >> >>> the first powered flight and so on, but who was the first to >> >>> describe the airforil as a component for 'heavier-than-air' flight? >> >> >>> Lilienthal used devices very similar to what we today would call >> >>> hang gliders a couple of decades before the Wrights got their >> >>> flyer together. I have seen claims that one of Lilienthal's main >> >>> contributions to aviation history was that he published a very >> >>> detailed description of the flight charactersitics of the airfoil >> >>> glider, >> >>> a description that turned out to be essential for e.g. the Wrights >> >>> to be able to build an actualair plane. >> >> >>> But describing the airfoil charactersitics is one thing - who >> >>> *invented* the airfoil? Was it ol'e Otto himself? Or somebody else? >> >> >>> Rune >> >> >> Birds have had them for a long time. =A0 Some flying reptiles before >> >> that. >> >> >> IIRC DaVinci did a bunch of sketches of bird wings and had various >> >> illustrated ideas about flying machines. >> >> >> I don't know if it's an "invention" if you just copy or adapt it offa>> >> bird. >> >> > Of course. But the question that popped into my head the other >> > day was who first described the airfoil as a viable method for >> > human aviation. Leonardo drew / fantasized about the thing, but >> > did not verify that it actually worked. >> >> > I suppose I'll settle for Lilienthal. >> >> I don't think you can settle for anyone, really -- from the link I >> posted it sounds like there were a number of people responding to the >> zeitgeist, who were all looking into airfoil theory at the same time. >> That sort of thing does sometimes coalesce out of thin air.=A0Lilienthal>> should get credit for his compendium, but I'm not so sure that heshould>> be credited as "the father of the airfoil" or anything. >> >> If you truly want to give credit to the invention of current airfoil >> theory, then look to the multitude of aerodynamic researchers whoworked>> between the world wars, and figured out the essential whys and >> wherefores of airfoils, and brought the world the standard subsonic >> airfoil shapes -- many of which are still being used. >> >> -- >> >> Tim Wescott >> Wescott Design Serviceshttp://www.wescottdesign.com >> >> Do you need to implement control loops in software? >> "Applied Control Theory for Embedded Systems" was written for you. >> See details athttp://www.wescottdesign.com/actfes/actfes.html > >A lot of "airfoil" development was done on blade shapes for turbines. >Even Pelton wheels has shaped buckets that are much more efficient >than simple vanes. The work of a turbine blade, boat sail, or airplane >wing is changing the direction (and perhaps speed) of the fluid >flowing past it. Doing that with minimum loss dictates that the >leading edge face directly into the impinging flow and that the >trailing edge be parallel to the departing flow. Clearly, that implies >a curved surface. For high-velocity flow, the usual teardrop >streamline shape reduces drag. Add that to the necessary curve, and >the classic airfoil shape is the result. At low speeds, the extra >weight of a thick wing is an impediment. The ROG models I built as a >kid all had wing covering only on the upper side. > >Oh: ROG stands for "rise off ground". These were rubber-powered planes >released on pavement or bare ground. > >JerryA lot of airfoil development occurred so long ago in Holland and East Anglia in England that nobody really knows the origins. What we do know is the traditional 4 sail windmill formed the sail into a basic airfoil section a very long time ago. In fact, when you consider how long ago the windmill makers had the basics of airfoil design in a practical form, its surprising wing design for aircraft took so long to figure out. Steve Steve
Reply by ●December 13, 20102010-12-13
On Nov 26, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote:> On Nov 25, 6:32�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > > > > > > > On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > > <all...@tele.ntnu.no> wrote: > > >Hi all. > > > >This is one of those questions that just popped into my mind > > >last night: Who invented / discovered the airfoil? Like in aviation > > >history. > > > >I know the Montgolfiers discovered the balloon, the Wright did > > >the first powered flight and so on, but who was the first to > > >describe the airforil as a component for 'heavier-than-air' flight? > > > >Lilienthal used devices very similar to what we today would call > > >hang gliders a couple of decades before the Wrights got their > > >flyer together. I have seen claims that one of Lilienthal's main > > >contributions to aviation history was that he published a very > > >detailed description of the flight charactersitics of the airfoil > > >glider, > > >a description that turned out to be essential for e.g. the Wrights > > >to be able to build an actualair plane. > > > >But describing the airfoil charactersitics is one thing - who > > >*invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > > >Rune > > > Birds have had them for a long time. � Some flying reptiles before > > that. > > > IIRC DaVinci did a bunch of sketches of bird wings and had various > > illustrated ideas about flying machines. > > > I don't know if it's an "invention" if you just copy or adapt it off a > > bird. > > Of course. But the question that popped into my head the other > day was who first described the airfoil as a viable method for > human aviation. Leonardo drew / fantasized about the thing, but > did not verify that it actually worked. > > I suppose I'll settle for Lilienthal. > > Rune- Hide quoted text - > > - Show quoted text -Rune, When we teach aviation here in the States, we attribute the mathematicall analysis/synthesis of the airfoil to Bournoulli's work with restricted fluid flow. By taking a cross-section (length wise) of Bournoulli's restricted tube, you have an airfoil. The venturi tube, used to generate a vaccum on early aircraft, is also based on this principal. Maurice Givens
Reply by ●December 13, 20102010-12-13
On Nov 25, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote:> Hi all. > > This is one of those questions that just popped into my mind > last night: Who invented / discovered the airfoil? Like in aviation > history. > > I know the Montgolfiers discovered the balloon, the Wright did > the first powered flight and so on, but who was the first to > describe the airforil as a component for 'heavier-than-air' flight? > > Lilienthal used devices very similar to what we today would call > hang gliders a couple of decades before the Wrights got their > flyer together. I have seen claims that one of Lilienthal's main > contributions to aviation history was that he published a very > detailed description of the flight charactersitics of the airfoil > glider, > a description that turned out to be essential for e.g. the Wrights > to be able to build an actualair plane. > > But describing the airfoil charactersitics is one thing - who > *invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > RuneZhukovsky invented the aifoil or, at least, was the first to compute its ideal profile mathematically http://en.wikipedia.org/wiki/Nikolai_Zhukovsky A lot of things you use every day (including DSP stuff) were invented by Russians Just remember this: never ever underestimate the Russians :-) (A lot of folks did in the past and they all regretted...) Happy new week, folks. Enjoy your Monday !
Reply by ●December 13, 20102010-12-13
On Dec 13, 10:51�am, maury <maury...@core.com> wrote:> On Nov 26, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > > > On Nov 25, 6:32�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > > > > On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > > > <all...@tele.ntnu.no> wrote: > > > >Hi all. > > > > >This is one of those questions that just popped into my mind > > > >last night: Who invented / discovered the airfoil? Like in aviation > > > >history. > > > > >I know the Montgolfiers discovered the balloon, the Wright did > > > >the first powered flight and so on, but who was the first to > > > >describe the airforil as a component for 'heavier-than-air' flight? > > > > >Lilienthal used devices very similar to what we today would call > > > >hang gliders a couple of decades before the Wrights got their > > > >flyer together. I have seen claims that one of Lilienthal's main > > > >contributions to aviation history was that he published a very > > > >detailed description of the flight charactersitics of the airfoil > > > >glider, > > > >a description that turned out to be essential for e.g. the Wrights > > > >to be able to build an actualair plane. > > > > >But describing the airfoil charactersitics is one thing - who > > > >*invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > > > >Rune > > > > Birds have had them for a long time. � Some flying reptiles before > > > that. > > > > IIRC DaVinci did a bunch of sketches of bird wings and had various > > > illustrated ideas about flying machines. > > > > I don't know if it's an "invention" if you just copy or adapt it off a > > > bird. > > > Of course. But the question that popped into my head the other > > day was who first described the airfoil as a viable method for > > human aviation. Leonardo drew / fantasized about the thing, but > > did not verify that it actually worked. > > > I suppose I'll settle for Lilienthal. > > > Rune- Hide quoted text - > > > - Show quoted text - > > Rune, > When we teach aviation here in the States, we attribute the > mathematicall analysis/synthesis of the airfoil to Bournoulli's work > with restricted fluid flow. By taking a cross-section (length wise) of > Bournoulli's restricted tube, you have an airfoil. The venturi tube, > used to generate a vaccum on early aircraft, is also based on this > principal.While the Bernoulli explanation of an airfoil is correct locally, accepting it as a complete explanation obscures the more general truth that an airfoil provides lift by imparting downward momentum to the fluid it passes through. The shape of a wing is material only for its efficiency -- read "lift-to-drag ratio." Glenn Curtis correctly observed that given an engine of sufficient power, he could fly a kitchen table. Naive application of the Bernoulli Principle to an airfoil doesn't make obvious that the pressure over the top of a wing being less than the pressure under it implies that air leaving the wing is accelerated downward. To put it differently, airfoils provide lift for the same reason that non-metallic sewer lines need anchor blocks wherever they turn corners. Jerry
Reply by ●December 13, 20102010-12-13
fatalist <simfidude@gmail.com> wrote: (snip)> A lot of things you use every day (including DSP stuff) were invented > by Russians > Just remember this: never ever underestimate the Russians :-) > (A lot of folks did in the past and they all regretted...)A lot of things that are used every day were invented by the Chinese, such as paper and gunpowder, and even catsup. What would we put on our french fries (that likely didn't originate in France) without the Chinese invention? -- glen
Reply by ●December 13, 20102010-12-13
On Dec 13, 1:00�pm, Jerry Avins <j...@ieee.org> wrote:> On Dec 13, 10:51�am, maury <maury...@core.com> wrote: > > > > > > > On Nov 26, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > > On Nov 25, 6:32�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > > > > > On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > > > > <all...@tele.ntnu.no> wrote: > > > > >Hi all. > > > > > >This is one of those questions that just popped into my mind > > > > >last night: Who invented / discovered the airfoil? Like in aviation > > > > >history. > > > > > >I know the Montgolfiers discovered the balloon, the Wright did > > > > >the first powered flight and so on, but who was the first to > > > > >describe the airforil as a component for 'heavier-than-air' flight? > > > > > >Lilienthal used devices very similar to what we today would call > > > > >hang gliders a couple of decades before the Wrights got their > > > > >flyer together. I have seen claims that one of Lilienthal's main > > > > >contributions to aviation history was that he published a very > > > > >detailed description of the flight charactersitics of the airfoil > > > > >glider, > > > > >a description that turned out to be essential for e.g. the Wrights > > > > >to be able to build an actualair plane. > > > > > >But describing the airfoil charactersitics is one thing - who > > > > >*invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > > > > >Rune > > > > > Birds have had them for a long time. � Some flying reptiles before > > > > that. > > > > > IIRC DaVinci did a bunch of sketches of bird wings and had various > > > > illustrated ideas about flying machines. > > > > > I don't know if it's an "invention" if you just copy or adapt it off a > > > > bird. > > > > Of course. But the question that popped into my head the other > > > day was who first described the airfoil as a viable method for > > > human aviation. Leonardo drew / fantasized about the thing, but > > > did not verify that it actually worked. > > > > I suppose I'll settle for Lilienthal. > > > > Rune- Hide quoted text - > > > > - Show quoted text - > > > Rune, > > When we teach aviation here in the States, we attribute the > > mathematicall analysis/synthesis of the airfoil to Bournoulli's work > > with restricted fluid flow. By taking a cross-section (length wise) of > > Bournoulli's restricted tube, you have an airfoil. The venturi tube, > > used to generate a vaccum on early aircraft, is also based on this > > principal. > > While the Bernoulli explanation of an airfoil is correct locally, > accepting it as a complete explanation obscures the more general truth > that an airfoil provides lift by imparting downward momentum to the > fluid it passes through. The shape of a wing is material only for its > efficiency -- read "lift-to-drag ratio." Glenn Curtis correctly > observed that given an engine of sufficient power, he could fly a > kitchen table. Naive application of the Bernoulli Principle to an > airfoil doesn't make obvious that the pressure over the top of a wing > being less than the pressure under it implies that air leaving the > wing is accelerated downward. To put it differently, airfoils provide > lift for the same reason that non-metallic sewer lines need anchor > blocks wherever they turn corners. > > Jerry- Hide quoted text - > > - Show quoted text -Jerry, Until about 5 years ago, whenever I had a new flight student I would take a piece of paper and blow over the top to show how it lifted due to reduced air pressure. Then I would blow on the bottom. Gee, when I blew on the bottom, it still lifted!! I taught the flight students that Bernoulli and Newton were at play. But, when taking the FAA written exam, only Bernoulli counted. About 5 years ago, everyone began to admit that Newton was also involved. The FAA study materials were also changed to give Newton credit. Maurice Givens
Reply by ●December 13, 20102010-12-13
On Dec 13, 3:53�pm, maury <maury...@core.com> wrote:> On Dec 13, 1:00�pm, Jerry Avins <j...@ieee.org> wrote: > > > > > On Dec 13, 10:51�am, maury <maury...@core.com> wrote: > > > > On Nov 26, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > > > On Nov 25, 6:32�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > > > > > > On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > > > > > <all...@tele.ntnu.no> wrote: > > > > > >Hi all. > > > > > > >This is one of those questions that just popped into my mind > > > > > >last night: Who invented / discovered the airfoil? Like in aviation > > > > > >history. > > > > > > >I know the Montgolfiers discovered the balloon, the Wright did > > > > > >the first powered flight and so on, but who was the first to > > > > > >describe the airforil as a component for 'heavier-than-air' flight? > > > > > > >Lilienthal used devices very similar to what we today would call > > > > > >hang gliders a couple of decades before the Wrights got their > > > > > >flyer together. I have seen claims that one of Lilienthal's main > > > > > >contributions to aviation history was that he published a very > > > > > >detailed description of the flight charactersitics of the airfoil > > > > > >glider, > > > > > >a description that turned out to be essential for e.g. the Wrights > > > > > >to be able to build an actualair plane. > > > > > > >But describing the airfoil charactersitics is one thing - who > > > > > >*invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > > > > > >Rune > > > > > > Birds have had them for a long time. � Some flying reptiles before > > > > > that. > > > > > > IIRC DaVinci did a bunch of sketches of bird wings and had various > > > > > illustrated ideas about flying machines. > > > > > > I don't know if it's an "invention" if you just copy or adapt it off a > > > > > bird. > > > > > Of course. But the question that popped into my head the other > > > > day was who first described the airfoil as a viable method for > > > > human aviation. Leonardo drew / fantasized about the thing, but > > > > did not verify that it actually worked. > > > > > I suppose I'll settle for Lilienthal. > > > > > Rune- Hide quoted text - > > > > > - Show quoted text - > > > > Rune, > > > When we teach aviation here in the States, we attribute the > > > mathematicall analysis/synthesis of the airfoil to Bournoulli's work > > > with restricted fluid flow. By taking a cross-section (length wise) of > > > Bournoulli's restricted tube, you have an airfoil. The venturi tube, > > > used to generate a vaccum on early aircraft, is also based on this > > > principal. > > > While the Bernoulli explanation of an airfoil is correct locally, > > accepting it as a complete explanation obscures the more general truth > > that an airfoil provides lift by imparting downward momentum to the > > fluid it passes through. The shape of a wing is material only for its > > efficiency -- read "lift-to-drag ratio." Glenn Curtis correctly > > observed that given an engine of sufficient power, he could fly a > > kitchen table. Naive application of the Bernoulli Principle to an > > airfoil doesn't make obvious that the pressure over the top of a wing > > being less than the pressure under it implies that air leaving the > > wing is accelerated downward. To put it differently, airfoils provide > > lift for the same reason that non-metallic sewer lines need anchor > > blocks wherever they turn corners. > > > Jerry- Hide quoted text - > > > - Show quoted text - > > Jerry, > Until about 5 years ago, whenever I had a new flight student I would > take a piece of paper and blow over the top to show how it lifted due > to reduced air pressure. Then I would blow on the bottom. Gee, when I > blew on the bottom, it still lifted!! I taught the flight students > that Bernoulli and Newton were at play. But, when taking the FAA > written exam, only Bernoulli counted. About 5 years ago, everyone > began to admit that Newton was also involved. The FAA study materials > were also changed to give Newton credit.It just goes to show how science -- science education, at least -- is subject to the same kind of changing fashion that governs what clothing is acceptable to wear. About 20 years ago, I (in my capacity as resident geek) was asked at a neighborhood cocktail party how a wing creates lift. I began with the example of a kite then, as questioner was a competent sailboater, with a sail set on a reach. I pointed out that the sail redirected air from across the deck to the stern. An efficient set of the sail occurs when the leading edge (luff) faces into the relative wind and the trailing edge (leach) points aft. Turn this arrangement on the side, and you have an airfoil. Pull the sail taut, as running close hauled, then add streamlining and voila! Something very like a Clark Y. A young fellow who had been standing behind me nearly knocked the drink out of my hand as he grabbed for my attention. He told me excitedly that he had just gotten his Master's in aeronautical engineering, and my explanation was the first time he understood how a wing worked. I think of that fellow with a shudder every time I fly in new design.
Reply by ●December 13, 20102010-12-13
On Dec 13, 2:00�pm, Jerry Avins <j...@ieee.org> wrote:> On Dec 13, 10:51�am, maury <maury...@core.com> wrote: > > > > > > > On Nov 26, 12:08�am, Rune Allnor <all...@tele.ntnu.no> wrote: > > > > On Nov 25, 6:32�pm, eric.jacob...@ieee.org (Eric Jacobsen) wrote: > > > > > On Wed, 24 Nov 2010 21:08:42 -0800 (PST), Rune Allnor > > > > > <all...@tele.ntnu.no> wrote: > > > > >Hi all. > > > > > >This is one of those questions that just popped into my mind > > > > >last night: Who invented / discovered the airfoil? Like in aviation > > > > >history. > > > > > >I know the Montgolfiers discovered the balloon, the Wright did > > > > >the first powered flight and so on, but who was the first to > > > > >describe the airforil as a component for 'heavier-than-air' flight? > > > > > >Lilienthal used devices very similar to what we today would call > > > > >hang gliders a couple of decades before the Wrights got their > > > > >flyer together. I have seen claims that one of Lilienthal's main > > > > >contributions to aviation history was that he published a very > > > > >detailed description of the flight charactersitics of the airfoil > > > > >glider, > > > > >a description that turned out to be essential for e.g. the Wrights > > > > >to be able to build an actualair plane. > > > > > >But describing the airfoil charactersitics is one thing - who > > > > >*invented* the airfoil? Was it ol'e Otto himself? Or somebody else? > > > > > >Rune > > > > > Birds have had them for a long time. � Some flying reptiles before > > > > that. > > > > > IIRC DaVinci did a bunch of sketches of bird wings and had various > > > > illustrated ideas about flying machines. > > > > > I don't know if it's an "invention" if you just copy or adapt it off a > > > > bird. > > > > Of course. But the question that popped into my head the other > > > day was who first described the airfoil as a viable method for > > > human aviation. Leonardo drew / fantasized about the thing, but > > > did not verify that it actually worked. > > > > I suppose I'll settle for Lilienthal. > > > > Rune- Hide quoted text - > > > > - Show quoted text - > > > Rune, > > When we teach aviation here in the States, we attribute the > > mathematicall analysis/synthesis of the airfoil to Bournoulli's work > > with restricted fluid flow. By taking a cross-section (length wise) of > > Bournoulli's restricted tube, you have an airfoil. The venturi tube, > > used to generate a vaccum on early aircraft, is also based on this > > principal. > > While the Bernoulli explanation of an airfoil is correct locally, > accepting it as a complete explanation obscures the more general truth > that an airfoil provides lift by imparting downward momentum to the > fluid it passes through. The shape of a wing is material only for its > efficiency -- read "lift-to-drag ratio." Glenn Curtis correctly > observed that given an engine of sufficient power, he could fly a > kitchen table. Naive application of the Bernoulli Principle to an > airfoil doesn't make obvious that the pressure over the top of a wing > being less than the pressure under it implies that air leaving the > wing is accelerated downward. To put it differently, airfoils provide > lift for the same reason that non-metallic sewer lines need anchor > blocks wherever they turn corners. > > Jerry- Hide quoted text - > > - Show quoted text -The curious thing about Bernoulli's formula is you don't see acceleration explicitly written in it. It does however have pressure (force per area) and Newton gave us via his 2nd law -> force = d/dt (momentum) which most 1st year students learn as simply F=ma. So with a physics viewpoint I see both being there since I know that Bernoulli can't violate Newton's laws of motion. So using Bernoulli's formulation without explicitly using Newton's laws is okay since they are buried in there anyway. Although your sewer pipe example is easy to understand in terms of accerated mass (acceration due to turning a corner). To apply Bernoulli's formula to the bent pipe problem is going to take more math to see how the radially dependent velocities results in radially dependent pressures thus yielding a net force on the pipe. This is not totally unlike Hamilton vs Lagrange's formulations for mechanics. I.e., position and momentum vs postion and velocity for your coordinates. It just depends on the problem as to which one yields the simplest solution. Clay
