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#41
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Lift - Newton/Bernoulli ratio...
On May 24, 10:35*am, Dudley Henriques
wrote: On May 23, 9:31*pm, a wrote: On May 22, 10:02*pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's principle might create 20% of the lift a wing generates. *A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. In this context, the meaning is, to produce the aircraft's weight in lift i.e. upwards , an airmass has to move *with sufficent acceleration to provide that up force. Bernoulii: the mass of air flowing through a channel times its speed gives the same product even if the channel then narrows to a waist: the air mass has to flow faster, but its pressure drops.. In this context: air flowing in an airstream over a wing sees it bulging (or waisting) and so that it needs to speed up, and pressure drops over the upper wing. Arguments of this type can be used as evidence that 2/3 of the wing lift is produced at the upper surface, and 1/3 at the lower wing surface. The larger truth: air pressure drops over the upper surface of a wing, and increases over the lower surface of a wing, and the resultant downflow balances the lift on the wing. Brian W *theories anyone here really believe there is no change in air density as if flows at speeds of a hundred miles an hour past an airfoil? The equation works well for water flow in pipes and around boat hulls. It does not do such a good job of predicting pressures along an airfoil. Stick with Newtonian Physics and the gas laws. The ideal gas law still applies. Compressing airflow does indeed complicate Bernoulli as do the density changes involved but Bernoulli still holds up. Both theories remain correct even with compressible flow. But you are correct in that the Newton explanation is FAR easier of the two for people to deal with and understand. The only caveat I stress to instructors when getting into the lift issue is that they NEVER explain lift using ONLY one theory without mention of the other, as student pilots, once exposed to the lift question will invariably find through a credible source that BOTH Newton and Bernoulli are correct and that each can explain exactly the same thing to the 100% point. Lift can be explained to death. The deeper one goes into the explanation the more complicated it can get. Denigrating Bernoulli due to changing density and airflow speeds causing compression factors is NOT the way to present lift. Bernoulli stands. It's the math that gets harder when you compress the flow that's all. All this can be avoided by simply explaining to students that lift results when an airflow is TURNED, and BOTH Newton and Bernoulli can be shown to cause the airflow to turn as lift is being produced. Circulation, density, vortices..........all part of it, but it's the turning of that airflow that produces lift force and BOTH Bernoulli and Newton are working equally to produce that force, only doing it differently. Dudley Henriques Actually, a quick meander through the literature will not find Bernoulli mentioned: in 2 D airflow studies it's gas laws and Newtonian physics, with a heavy emphasis on experimental results. These days, numerical methods -- what we used to call difference equations -- seem to yield results that seem to come pretty close to predicting experimental results. Notice especially in experiments that chord sections have end plates so that flow really is confined to 2 D. What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! It's nice to see a real aviation topic here, isn't it? |
#42
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Lift - Newton/Bernoulli ratio...
On May 24, 10:03*pm, a wrote:
On May 24, 10:35*am, Dudley Henriques wrote: On May 23, 9:31*pm, a wrote: On May 22, 10:02*pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's principle might create 20% of the lift a wing generates. *A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. In this context, the meaning is, to produce the aircraft's weight in lift i.e. upwards , an airmass has to move *with sufficent acceleration to provide that up force. Bernoulii: the mass of air flowing through a channel times its speed gives the same product even if the channel then narrows to a waist: the air mass has to flow faster, but its pressure drops.. In this context: air flowing in an airstream over a wing sees it bulging (or waisting) and so that it needs to speed up, and pressure drops over the upper wing. Arguments of this type can be used as evidence that 2/3 of the wing lift is produced at the upper surface, and 1/3 at the lower wing surface. The larger truth: air pressure drops over the upper surface of a wing, and increases over the lower surface of a wing, and the resultant downflow balances the lift on the wing. Brian W *theories anyone here really believe there is no change in air density as if flows at speeds of a hundred miles an hour past an airfoil? The equation works well for water flow in pipes and around boat hulls. It does not do such a good job of predicting pressures along an airfoil. Stick with Newtonian Physics and the gas laws. The ideal gas law still applies. Compressing airflow does indeed complicate Bernoulli as do the density changes involved but Bernoulli still holds up. Both theories remain correct even with compressible flow. But you are correct in that the Newton explanation is FAR easier of the two for people to deal with and understand. The only caveat I stress to instructors when getting into the lift issue is that they NEVER explain lift using ONLY one theory without mention of the other, as student pilots, once exposed to the lift question will invariably find through a credible source that BOTH Newton and Bernoulli are correct and that each can explain exactly the same thing to the 100% point. Lift can be explained to death. The deeper one goes into the explanation the more complicated it can get. Denigrating Bernoulli due to changing density and airflow speeds causing compression factors is NOT the way to present lift. Bernoulli stands. It's the math that gets harder when you compress the flow that's all. All this can be avoided by simply explaining to students that lift results when an airflow is TURNED, and BOTH Newton and Bernoulli can be shown to cause the airflow to turn as lift is being produced. Circulation, density, vortices..........all part of it, but it's the turning of that airflow that produces lift force and BOTH Bernoulli and Newton are working equally to produce that force, only doing it differently. Dudley Henriques Actually, a quick meander through the literature will not find Bernoulli mentioned: in 2 D airflow studies it's gas laws and Newtonian physics, with a heavy emphasis on experimental results. These days, numerical methods -- what we used to call difference equations -- seem to yield results that seem to come pretty close to predicting experimental results. Notice especially in experiments that chord sections have end plates so that flow really is confined to 2 D. What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. *I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. *My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! It's nice to see a real aviation topic here, isn't it? I don't know what "literature" you're referring to that doesn't mention Bernoulli when discussing lift, but I'd avoid that literature if I were you. It's incomplete! :-)) DH |
#44
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Lift - Newton/Bernoulli ratio...
On May 25, 2:36*am, Dave Doe wrote:
In article 6469c134-67e0-4ca9-8dd1- , , a says... On May 24, 10:35*am, Dudley Henriques wrote: On May 23, 9:31*pm, a wrote: On May 22, 10:02*pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's principle might create 20% of the lift a wing generates. *A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. In this context, the meaning is, to produce the aircraft's weight in lift i.e. upwards , an airmass has to move *with sufficent acceleration to provide that up force. Bernoulii: the mass of air flowing through a channel times its speed gives the same product even if the channel then narrows to a waist: the air mass has to flow faster, but its pressure drops.. In this context: air flowing in an airstream over a wing sees it bulging (or waisting) and so that it needs to speed up, and pressure drops over the upper wing. Arguments of this type can be used as evidence that 2/3 of the wing lift is produced at the upper surface, and 1/3 at the lower wing surface. The larger truth: air pressure drops over the upper surface of a wing, and increases over the lower surface of a wing, and the resultant downflow balances the lift on the wing. Brian W *theories anyone here really believe there is no change in air density as if flows at speeds of a hundred miles an hour past an airfoil? The equation works well for water flow in pipes and around boat hulls. It does not do such a good job of predicting pressures along an airfoil. Stick with Newtonian Physics and the gas laws. The ideal gas law still applies. Compressing airflow does indeed complicate Bernoulli as do the density changes involved but Bernoulli still holds up. Both theories remain correct even with compressible flow. But you are correct in that the Newton explanation is FAR easier of the two for people to deal with and understand. The only caveat I stress to instructors when getting into the lift issue is that they NEVER explain lift using ONLY one theory without mention of the other, as student pilots, once exposed to the lift question will invariably find through a credible source that BOTH Newton and Bernoulli are correct and that each can explain exactly the same thing to the 100% point. Lift can be explained to death. The deeper one goes into the explanation the more complicated it can get. Denigrating Bernoulli due to changing density and airflow speeds causing compression factors is NOT the way to present lift. Bernoulli stands. It's the math that gets harder when you compress the flow that's all. All this can be avoided by simply explaining to students that lift results when an airflow is TURNED, and BOTH Newton and Bernoulli can be shown to cause the airflow to turn as lift is being produced. Circulation, density, vortices..........all part of it, but it's the turning of that airflow that produces lift force and BOTH Bernoulli and Newton are working equally to produce that force, only doing it differently. Dudley Henriques Actually, a quick meander through the literature will not find Bernoulli mentioned: in 2 D airflow studies it's gas laws and Newtonian physics, with a heavy emphasis on experimental results. These days, numerical methods -- what we used to call difference equations -- seem to yield results that seem to come pretty close to predicting experimental results. Notice especially in experiments that chord sections have end plates so that flow really is confined to 2 D. What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. *I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. *My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! It's nice to see a real aviation topic here, isn't it? Have a look at this one that I found late last night - check the section out on Wing Efficiency - and the sections beyond it... comments welcomed http://home.comcast.net/~clipper-108/lift.pdf -- Duncan. I didn't have to get past the first several paragraphs to see what was going on here with this paper. It becomes apparent with the sentence, "Bernoulli relies on equal transit times". This statement is false on premise so all that comes after it has to be flawed. Bernoulli absolutely and most certainly does NOT rely on equal transit. Equal transit is incorrect in ALL explanations on lift development and in fact is probably responsible for more misunderstanding about Bernoulli that anything else. This paper represents just more of the misunderstanding surrounding lift. It looks good on the face, is well written, but misses the basic point that you don't need equal transit to prove Bernoulli. The main point this paper makes is that if you believe you need equal transit to prove Bernoulli you need to dig into lift development a bit deeper, especially the Bernoulli end of things. Point of note; Be wary of any and all papers on this subject written by individuals. Be wary of me as well. Do some SERIOUS homework on this if you are really interested. One of the most credible, if not THE most credible text ever written on these subjects is the bible I have used myself all through my career, and recommended to every instructor and pilot who has ever crossed my path. The book is well worth the money and every serious pilot should own a copy. It's a bit heavy on math but crystal clear on explanation. Get a copy of "Aerodynamics For Naval Aviators" by Hurt. Read the section on lift and you will never again have any doubt at all about either Newton or Bernoulli being a 100% explanation for how lift is createdi. Dudley Henriques |
#45
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Lift - Newton/Bernoulli ratio...
On 2011-05-25, a wrote:
What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! The reason why is that you have tradeoffs - long and slender wings won't work so well for a much heavier plane (more heavy structure) that has to go much faster (more form drag). Even performance gliders are slow compared to, say, a Beech Bonanza (I got all excited about flying a Discus, now I could transit across areas of sink at a whopping 90 knots or so). Some 4 seat planes have longer, higher aspect ratio wings than was traditional, for instance the Diamond DA-40 which has trouble fitting in a lot of T-hangars due to its wingspan of 40-odd feet. However I suspect much beyond that wingspan you're going to start losing more than you gain in parasitic drag and extra structural weight to have a very long, slender wing in a 4 seat plane that goes more than 140 knots in cruise. |
#46
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Lift - Newton/Bernoulli ratio...
On May 26, 1:06*am, Dudley Henriques
wrote: On May 25, 2:36*am, Dave Doe wrote: In article 6469c134-67e0-4ca9-8dd1- , , a says.... On May 24, 10:35*am, Dudley Henriques wrote: On May 23, 9:31*pm, a wrote: On May 22, 10:02*pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's principle might create 20% of the lift a wing generates. *A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. In this context, the meaning is, to produce the aircraft's weight in lift i.e. upwards , an airmass has to move *with sufficent acceleration to provide that up force. Bernoulii: the mass of air flowing through a channel times its speed gives the same product even if the channel then narrows to a waist: the air mass has to flow faster, but its pressure drops.. In this context: air flowing in an airstream over a wing sees it bulging (or waisting) and so that it needs to speed up, and pressure drops over the upper wing. Arguments of this type can be used as evidence that 2/3 of the wing lift is produced at the upper surface, and 1/3 at the lower wing surface. The larger truth: air pressure drops over the upper surface of a wing, and increases over the lower surface of a wing, and the resultant downflow balances the lift on the wing. Brian W *theories anyone here really believe there is no change in air density as if flows at speeds of a hundred miles an hour past an airfoil? The equation works well for water flow in pipes and around boat hulls.. It does not do such a good job of predicting pressures along an airfoil. Stick with Newtonian Physics and the gas laws. The ideal gas law still applies. Compressing airflow does indeed complicate Bernoulli as do the density changes involved but Bernoulli still holds up. Both theories remain correct even with compressible flow. But you are correct in that the Newton explanation is FAR easier of the two for people to deal with and understand. The only caveat I stress to instructors when getting into the lift issue is that they NEVER explain lift using ONLY one theory without mention of the other, as student pilots, once exposed to the lift question will invariably find through a credible source that BOTH Newton and Bernoulli are correct and that each can explain exactly the same thing to the 100% point. Lift can be explained to death. The deeper one goes into the explanation the more complicated it can get. Denigrating Bernoulli due to changing density and airflow speeds causing compression factors is NOT the way to present lift. Bernoulli stands. It's the math that gets harder when you compress the flow that's all. All this can be avoided by simply explaining to students that lift results when an airflow is TURNED, and BOTH Newton and Bernoulli can be shown to cause the airflow to turn as lift is being produced. Circulation, density, vortices..........all part of it, but it's the turning of that airflow that produces lift force and BOTH Bernoulli and Newton are working equally to produce that force, only doing it differently. Dudley Henriques Actually, a quick meander through the literature will not find Bernoulli mentioned: in 2 D airflow studies it's gas laws and Newtonian physics, with a heavy emphasis on experimental results. These days, numerical methods -- what we used to call difference equations -- seem to yield results that seem to come pretty close to predicting experimental results. Notice especially in experiments that chord sections have end plates so that flow really is confined to 2 D.. What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. *I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. *My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! It's nice to see a real aviation topic here, isn't it? Have a look at this one that I found late last night - check the section out on Wing Efficiency - and the sections beyond it... comments welcomed http://home.comcast.net/~clipper-108/lift.pdf -- Duncan. I didn't have to get past the first several paragraphs to see what was going on here with this paper. It becomes apparent with the sentence, "Bernoulli relies on equal transit times". This statement is false on premise so all that comes after it has to be flawed. Bernoulli absolutely and most certainly does NOT rely on equal transit. Equal transit is incorrect in ALL explanations on lift development and in fact is probably responsible for more misunderstanding about Bernoulli that anything else. This paper represents just more of the misunderstanding surrounding lift. It looks good on the face, is well written, but misses the basic point that you don't need equal transit to prove Bernoulli. The main point this paper makes is that if you believe you need equal transit to prove Bernoulli you need to dig into lift development a bit deeper, especially the Bernoulli end of things. Point of note; Be wary of any and all papers on this subject written by individuals. Be wary of me as well. Do some SERIOUS homework on this if you are really interested. One of the most credible, if not THE most credible text ever written on these subjects is the bible I have used myself all through my career, and recommended to every instructor *and pilot who has ever crossed my path. The book is well worth the money and every serious pilot should own a copy. It's a bit heavy on math but crystal clear on explanation. Get a copy of "Aerodynamics For Naval Aviators" by Hurt. Read the section on lift and you will never again have any doubt at all about either Newton or Bernoulli being a 100% explanation for how lift is createdi. Dudley Henriques Yup Or "Flight without Formulae" for simple easy to understand reading to prepare one for the more complex explanations out there... |
#47
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Lift - Newton/Bernoulli ratio...
In article 47971036-2b4d-4297-bcbf-
, , Dudley Henriques says... On May 25, 2:36*am, Dave Doe wrote: In article 6469c134-67e0-4ca9-8dd1- , , a says... On May 24, 10:35*am, Dudley Henriques wrote: On May 23, 9:31*pm, a wrote: On May 22, 10:02*pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's principle might create 20% of the lift a wing generates. *A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. In this context, the meaning is, to produce the aircraft's weight in lift i.e. upwards , an airmass has to move *with sufficent acceleration to provide that up force. Bernoulii: the mass of air flowing through a channel times its speed gives the same product even if the channel then narrows to a waist: the air mass has to flow faster, but its pressure drops.. In this context: air flowing in an airstream over a wing sees it bulging (or waisting) and so that it needs to speed up, and pressure drops over the upper wing. Arguments of this type can be used as evidence that 2/3 of the wing lift is produced at the upper surface, and 1/3 at the lower wing surface. The larger truth: air pressure drops over the upper surface of a wing, and increases over the lower surface of a wing, and the resultant downflow balances the lift on the wing. Brian W *theories anyone here really believe there is no change in air density as if flows at speeds of a hundred miles an hour past an airfoil? The equation works well for water flow in pipes and around boat hulls. It does not do such a good job of predicting pressures along an airfoil. Stick with Newtonian Physics and the gas laws. The ideal gas law still applies. Compressing airflow does indeed complicate Bernoulli as do the density changes involved but Bernoulli still holds up. Both theories remain correct even with compressible flow. But you are correct in that the Newton explanation is FAR easier of the two for people to deal with and understand. The only caveat I stress to instructors when getting into the lift issue is that they NEVER explain lift using ONLY one theory without mention of the other, as student pilots, once exposed to the lift question will invariably find through a credible source that BOTH Newton and Bernoulli are correct and that each can explain exactly the same thing to the 100% point. Lift can be explained to death. The deeper one goes into the explanation the more complicated it can get. Denigrating Bernoulli due to changing density and airflow speeds causing compression factors is NOT the way to present lift. Bernoulli stands. It's the math that gets harder when you compress the flow that's all. All this can be avoided by simply explaining to students that lift results when an airflow is TURNED, and BOTH Newton and Bernoulli can be shown to cause the airflow to turn as lift is being produced. Circulation, density, vortices..........all part of it, but it's the turning of that airflow that produces lift force and BOTH Bernoulli and Newton are working equally to produce that force, only doing it differently. Dudley Henriques Actually, a quick meander through the literature will not find Bernoulli mentioned: in 2 D airflow studies it's gas laws and Newtonian physics, with a heavy emphasis on experimental results. These days, numerical methods -- what we used to call difference equations -- seem to yield results that seem to come pretty close to predicting experimental results. Notice especially in experiments that chord sections have end plates so that flow really is confined to 2 D. What is really interesting is that high performance glider wings are long and slender: that's how they get the most efficient use of potential energy in the form of altitude and turn it into range. *I don't know of any 4 seat complex SEL that uses the same principle and am not sure why. *My Mooney gets 20 mpg or so, sure would enjoy seeing that change to 30! It's nice to see a real aviation topic here, isn't it? Have a look at this one that I found late last night - check the section out on Wing Efficiency - and the sections beyond it... comments welcomed http://home.comcast.net/~clipper-108/lift.pdf -- Duncan. I didn't have to get past the first several paragraphs to see what was going on here with this paper. It becomes apparent with the sentence, "Bernoulli relies on equal transit times". This statement is false on premise so all that comes after it has to be flawed. Bernoulli absolutely and most certainly does NOT rely on equal transit. Equal transit is incorrect in ALL explanations on lift I don't think you read or understood the paper very well. The author is saying that that is the common misconception - he terms it, "Popular Description" - which he points out is incorrect - as you do. -- Duncan. |
#48
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Lift - Newton/Bernoulli ratio...
On May 25, 6:55*pm, Dave Doe wrote:
In article 47971036-2b4d-4297-bcbf- , , Dudley Henriques says... On May 25, 2:36 am, Dave Doe wrote: In article 6469c134-67e0-4ca9-8dd1- , , a says.... On May 24, 10:35 am, Dudley Henriques wrote: On May 23, 9:31 pm, a wrote: On May 22, 10:02 pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. I would guess that Bernoulli's principle might create 20% of the lift a wing generates. A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. |
#49
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Lift - Newton/Bernoulli ratio...
On May 25, 6:55*pm, Dave Doe wrote:
In article 47971036-2b4d-4297-bcbf- , , Dudley Henriques says... On May 25, 2:36 am, Dave Doe wrote: In article 6469c134-67e0-4ca9-8dd1- , , a says.... On May 24, 10:35 am, Dudley Henriques wrote: On May 23, 9:31 pm, a wrote: On May 22, 10:02 pm, brian whatcott wrote: On 5/22/2011 5:15 AM, Dave Doe wrote: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? I appreciate this is not a static figure - but say a yer average C-172, or perhaps a 737. I would hazard a semi-educated guess that lift is *primarily* produced by angle of attack (or deflection if you like) - Newton's Laws - and by a much lesser degree by Bernoulli's Law. I would guess that Bernoulli's principle might create 20% of the lift a wing generates. A friend believes it would be much lesser - about 5%. Think of it this way: Newton: force is proportional to the mass and its acceleration. |
#50
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Lift - Newton/Bernoulli ratio...
Dave Doe writes:
If you are right, I'd expect to see planes with the airfoil upsidedown (with the increased camber on the bottom), but that's not the case (and I'm talking about the *wings* here, not the horizontal stabiliser Actually it is. NASA has tested airfoils with a camber on the bottom, and they fly just as well as airfoils with a camber on the top. I don't know what became of the research, though. As a I recall, they had some airfoils that were very good at preventing stalls, but I suppose they had other disadvantages (drag problems?). I think you have explained though, that the Bernoulli effect occurs with a barn door too at an angle of attack - however it is a lot less *efficient* without that camber (which will continue to 'suck' air down - as the camber continues to change direction - and therefore drag the viscous air around it with it). I hope you'll agree with that. Good airfoil designs can reduce drag and improve stall characteristics, but generating lift requires only a positive angle of attack. |
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