If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
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%. -- Duncan. |
#2
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
In article ,
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%. Newton and Bernoulli approach the idea of lift generation from two different perspectives -- both correct. Newton's laws explain lift as an exchange of energy and momentum -- a craft flying through the air imparts some of its momentum to the vertical axis, which manifests itself as "lift." Bernoulli explains the fluid mechanics of lift generation via pressure distribution, to create "lift." Newton explains why we get a downdraft as a plane flies overhead. |
#3
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
Dave Doe writes:
Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? All lift is produced by Newton's third law of motion. Air is forced downwards by the wings, and this produces an equal and opposite force that attempts to raise the wings, and that is lift. How the air is forced downwards is irrelevant, as long as it happens. In practice, principles discovered by Bernoulli and others play a role in diverting the air flow when this is accomplished by an airfoil. |
#4
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
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 |
#5
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
|
#6
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
|
#7
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
On May 22, 7:04*pm, Mxsmanic wrote:
Dave Doe writes: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? All lift is produced by Newton's third law of motion. Air is forced downwards by the wings, and this produces an equal and opposite force that attempts to raise the wings, and that is lift. How the air is forced downwards is irrelevant, as long as it happens. In practice, principles discovered by Bernoulli and others play a role in diverting the air flow when this is accomplished by an airfoil. Actually, if I'm reading you right, I would rephrase this just a bit, as it feeds into the problems we as instructors have in "re- explaining" lift to students. STRESSING either Newton or Bernoulli in the lift explanation causes more than a modicum of confusion UNLESS it's done by including BOTH theories in the explanation. You've done that actually. I would just enhance things a bit more :-) Read what Orval says above. He is absolutely correct. BOTH Newton and Bernoulli are COMPLETE explanations for lift, which is interesting in another respect, as neither man had lift in mind with their work. The simple truth of it is that each explanation is totally correct and is interchangeable with the other. Each explains the same thing without relying on the other and BOTH are occurring simultaneously. It's a common misconception that Bernoulli and Newton EACH contribute INDIVIDUALLY to form a TOTAL of the lift produced. This explanation is incorrect and should be discouraged. When I dealt with the lift issue with instructors in seminar, my personal approach was to favor the Newtonian explanation as in my opinion student pilots can grasp Newton a lot easier than Bernoulli, but I've ALWAYS made it habit NEVER to leave Bernoulli out in the cold. The correct way to deal with the lift issue is to explain to those asking that BOTH explanations are complete by themselves, and Newton might be the easier of the two to explain. Dudley Henriques |
#9
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
In article 4f56d67d-f259-46e7-8e3f-
, , Dudley Henriques says... On May 22, 7:04*pm, Mxsmanic wrote: Dave Doe writes: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? All lift is produced by Newton's third law of motion. Air is forced downwards by the wings, and this produces an equal and opposite force that attempts to raise the wings, and that is lift. How the air is forced downwards is irrelevant, as long as it happens. In practice, principles discovered by Bernoulli and others play a role in diverting the air flow when this is accomplished by an airfoil. Actually, if I'm reading you right, I would rephrase this just a bit, as it feeds into the problems we as instructors have in "re- explaining" lift to students. STRESSING either Newton or Bernoulli in the lift explanation causes more than a modicum of confusion UNLESS it's done by including BOTH theories in the explanation. You've done that actually. I would just enhance things a bit more :-) Read what Orval says above. He is absolutely correct. BOTH Newton and Bernoulli are COMPLETE explanations for lift, which is interesting in another respect, as neither man had lift in mind with their work. The simple truth of it is that each explanation is totally correct and is interchangeable with the other. Each explains the same thing without relying on the other and BOTH are occurring simultaneously. It's a common misconception that Bernoulli and Newton EACH contribute INDIVIDUALLY to form a TOTAL of the lift produced. This explanation is incorrect and should be discouraged. While it's true that the Bernoulli effect is part of Newtonian mechanics - I want to know what the ratio of (gonna have to rephrase this aren't I) is: * an airfoil where the camber on both sides is equal and opposite (mirroed) vs * an airfoil that is shaped to produce lift via Bernoulli effect. When I dealt with the lift issue with instructors in seminar, my personal approach was to favor the Newtonian explanation as in my opinion student pilots can grasp Newton a lot easier than Bernoulli, but I've ALWAYS made it habit NEVER to leave Bernoulli out in the cold. The correct way to deal with the lift issue is to explain to those asking that BOTH explanations are complete by themselves, and Newton might be the easier of the two to explain. Dudley Henriques I'll rephrase it a second time. What percentage of extra lift is gained from: a) a plank of wood (can only produce lift via angle of attack) vs b) a plank of wood that is an airfoil - and is getting lift from both angle of attack and the Bernoulli effect. I hope that is clearer. Here are some articles - but they produce no data to show the addidtional lift obtained by the Bernoulli effect. http://en.wikipedia.org/wiki/Airfoil http://en.wikipedia.org/wiki/NACA_airfoil http://en.wikipedia.org/wiki/Lift_(force) http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html And here is a third re-phrase... * A yacht that has a sail made of unbendable stiff material (will not point as high and go as fast as)... * A yacht that has a sail of normal material and has an effective airfoil shape and produces lift perpendicular to the sail (via the Bernoulli effect). Is it not a simple enough question? - I mean, really. While results will undoubtably vary among plane types and airspeed - I'm just looking for an approximate percentage. Do read that: http://en.wikipedia.org/wiki/NACA_airfoil page! And I don't want to get stuck on the pedantics of Newtonian physics encompassing the Bernoulli effect - just really looking at, as said (rephrase #4)... - lift produced by an airfoil that has a mirrored camber top and bottom (the zero lift line is the same as the chord line) vs - lift produced by a traditional airfoil -- Duncan. |
#10
|
|||
|
|||
Lift - Newton/Bernoulli ratio...
In article , er, Private
says... "Dave Doe" wrote in message ... In article , , Mxsmanic says... Dave Doe writes: Does anyone have any figures and references for about what ratio lift is produced by Newton's Laws and Bernoulli's Laws? All lift is produced by Newton's third law of motion. Air is forced downwards by the wings, and this produces an equal and opposite force that attempts to raise the wings, and that is lift. How the air is forced downwards is irrelevant, as long as it happens. In practice, principles discovered by Bernoulli and others play a role in diverting the air flow when this is accomplished by an airfoil. As said in other reply - not looking for a run-down on the physics - looking for the *ratio* of lift obtained by each. -- Duncan. Simple answer, there is no "ratio" - Newton 100% + Bernoulli 100%, total = 100% So a wing generates as much lift upside down? What I want, is half the difference between a wing up the right way, and the wing up the wrong way. That is, I presume, the additional lifting force from the Bernoulli effect vs a wing with a mirrored camber (obtaining no lift due to the Bernoulli effect). It really is a "chicken or egg" question. Google "Newton vs. Bernoulli" and "Newton vs. Bernoulli" NASA Perhaps it is. I have googled. I recommend http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html Been there. and much more http://www.grc.nasa.gov/WWW/K-12/airplane/short.html And there. When done you can also work (troll?) on other important old disputes regarding - high wing vs. low wing, track up vs. north up, and slip vs. crab with a kick. Happy landings, Not interested in trolling. If you think I am, please do not reply, or reply and say so, and I will do as such. -- Duncan. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Three take offs = three landings at Newton MS and Madison MS - Video | [email protected] | Piloting | 39 | November 28th 09 01:22 AM |
How can the Magnus effect be explained with Bernoulli? | Mikki | Piloting | 4 | June 24th 09 05:51 AM |
Lift-to-Drag Ratio? | Toks Desalu | Home Built | 6 | November 23rd 03 10:53 PM |
The bernoulli theory of starting a long thread | David CL Francis | Piloting | 7 | October 26th 03 07:40 PM |
worked fairly well - the German 37mm and British 40mm, frank mitch newton on Stukas | fmn2 | Naval Aviation | 1 | August 10th 03 02:14 AM |