Why do people say the top of the wing causes the plane to fly?
10-03-2008, 12:29 PM
#226
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RE: [Deleted]
ORIGINAL: Rocketmagnet
Mike's specific question was "Why do people say the top of the wing causes the plane to fly?"
...
Mike's specific question was "Why do people say the top of the wing causes the plane to fly?"
...
The differential makes sense and seems to fall into Newton's law of every action must have an opposite and equal reaction.
EDIT: forgot to put the word "opposite" in there.
10-03-2008, 12:57 PM
#227
RE: [Deleted]
ORIGINAL: ArCeeFlyer
Then the real question is basically a human psychology one and not so much an aerodynamic one. It may have to do with all the mystery generated by the top of the wing as this thread really shows.
The differential makes sense and seems to fall into Newton's law of every action must have an opposite and equal reaction.
EDIT: forgot to put the word "opposite" in there.
ORIGINAL: Rocketmagnet
Mike's specific question was "Why do people say the top of the wing causes the plane to fly?"
...
Mike's specific question was "Why do people say the top of the wing causes the plane to fly?"
...
The differential makes sense and seems to fall into Newton's law of every action must have an opposite and equal reaction.
EDIT: forgot to put the word "opposite" in there.
So-
As for the fun questions:
Why are there different species ?
Good question in that we all evolved from ONE:
Why do planets move in an ellipse?
The gravity of that question escapes me.
"Why do people say the top of the wing causes a plane to fly?"
Answer : because they do not understand the CONCEPT of what the wing does.
10-03-2008, 01:19 PM
#228
RE: [Deleted]
I often quote equations because there is safety in something that cannot be disputed. However, to convey a visceral feel for whats going on with a wing we need concrete observable examples.
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
10-03-2008, 01:36 PM
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RE: [Deleted]
ORIGINAL: CrateCruncher
I often quote equations because there is safety in something that cannot be disputed. However, to convey a visceral feel for whats going on with a wing we need concrete observable examples.
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
I often quote equations because there is safety in something that cannot be disputed. However, to convey a visceral feel for whats going on with a wing we need concrete observable examples.
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
For some reason, I understood all that.
Makes sense to me.
So when people say a plane flies because of the shape of the top wing, they aren't but 50% correct.
10-03-2008, 02:41 PM
#230
RE: [Deleted]
ORIGINAL: Mike SVOR
For some reason, I understood all that.
Makes sense to me.
So when people say a plane flies because of the shape of the top wing, they aren't but 50% correct.
ORIGINAL: CrateCruncher
I often quote equations because there is safety in something that cannot be disputed. However, to convey a visceral feel for whats going on with a wing we need concrete observable examples.
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
I often quote equations because there is safety in something that cannot be disputed. However, to convey a visceral feel for whats going on with a wing we need concrete observable examples.
Gas behaves in a very predictable way. It ALWAYS moves from high pressure to low pressure - the rate of acceleration being proportional to the difference in pressure. Wind on your face is an obvious example.
As the wing translates through the gas a lower than ambient pressure develops on the top of the airfoil and a higher pressure than ambient develops underneath the wing. This can be measured and has been, ad nauseum. The relative contribution between upper and lower varies with shape, speed, AoA, etc. If you must know more you will have to delve into the nerdy world of technical books on the subject, they are cheap and plentiful.
The undisturbed air above the wing accelerates toward the low pressure disturbance on the top rear surface of the airfoil and the high pressure gas pocket underneath the wing moves toward the undisturbed air at ambient pressure below it.
The result of all this air movement is a large mass of air being accelerated downward due to the pressure change. It can be described with the downwash angle. The reaction to this air acceleration is that the wing accelerates upward in the opposite direction or in the case of level flight, simply opposes the acceleration of gravity.
A propeller is a wing that rotates very, very fast. When you rev an RC plane the prop produces rearward thrust (aka downwash) and the entire plane reacts in the opposite direction. A helicopter has a similar dynamic.
Wait you say! Why wouldn't the high pressure on bottom move toward the low pressure on top and cause the wing to accelerate downward. The wing keeps the two separate until the classical air acceleration has become established except at the tip where this is precisely what occurs! The air from the bottom of the wing moves around the tip to the top creating pretty helical vortices we've all seen in smoke tests.
And it all relates back to pressure differential in a gas. Note that I have simplified some things in order to make it more readable but hey I didn't bore anyone with math....
For some reason, I understood all that.
Makes sense to me.
So when people say a plane flies because of the shape of the top wing, they aren't but 50% correct.
It's the Ying to the Yang.
10-03-2008, 04:16 PM
#231
RE: [Deleted]
Excellent post CrateCruncher!!...it made sense to Mike!
Mike:
I would recommend you to read the Aerodynamics’ thread Bernoulli vs Newton started by Tall Paul 5/18/08.
There are many interesting posts there that will help you understand that the whole lift on an airfoil is not a black and white simple phenomenon.
It is very complicated to understand and to explain, and it has not been completely understood for many airfoils used in model airplanes, where the Re number is too low.
However, it is not mystery.
Asking for the excuse of any purist out there, I just want to help you understand your own question with a similarity I have thought:
Just imagine a plane surface being forced to move horizontally through sand, at a small positive angle, like an airfoil moves through the atmosphere.
Lift, drag, etc. are proportional to the square of velocity.
Due to that dependence, air shows a very soft (or gas type) reaction to any surface that moves at low velocities, but it reacts harder (or solid type) to surfaces moving very fast.
So, we could assume that our example would be the extreme case for high velocity.
Imagine what happen to the sand on both surfaces of the plane:
The bottom sand gets compacted and dragged by the moving plane, which tends to ramp (slide) up following its angle by pushing down.
The top sand gets loosen by the moving plane, and it tends to roll down the plane following its angle. Sand way above will tend to fall down by its weight to fill up the loosen space.
Is it not something similar to what the video posted by Rocket Magnet shows happens with the air?
Notice that the air against the moving bottom surface is accelerated by the airfoil to a velocity smaller than its own velocity through the air. I believe that is natural, if it gets compacted and dragged like the sand of our experiment. Notice that the upwash in front of the airfoil is a result of this.
Also notice that the air against the moving top surface is accelerated by the airfoil to a velocity higher than its own velocity through the air. I believe that is natural, if it gets loosen (or expanded) and slides down like the sand of our experiment. Notice that the downwash behind the airfoil is a result of this.
For normal level flight, our plane is ramping up on the air (not too soft, not too hard) at the same rate that it naturally falls.
The airfoil uses its velocity energy to grab the air and hang from it, while the air gains that energy.
Lnewqban
Mike:
I would recommend you to read the Aerodynamics’ thread Bernoulli vs Newton started by Tall Paul 5/18/08.
There are many interesting posts there that will help you understand that the whole lift on an airfoil is not a black and white simple phenomenon.
It is very complicated to understand and to explain, and it has not been completely understood for many airfoils used in model airplanes, where the Re number is too low.
However, it is not mystery.
Asking for the excuse of any purist out there, I just want to help you understand your own question with a similarity I have thought:
Just imagine a plane surface being forced to move horizontally through sand, at a small positive angle, like an airfoil moves through the atmosphere.
Lift, drag, etc. are proportional to the square of velocity.
Due to that dependence, air shows a very soft (or gas type) reaction to any surface that moves at low velocities, but it reacts harder (or solid type) to surfaces moving very fast.
So, we could assume that our example would be the extreme case for high velocity.
Imagine what happen to the sand on both surfaces of the plane:
The bottom sand gets compacted and dragged by the moving plane, which tends to ramp (slide) up following its angle by pushing down.
The top sand gets loosen by the moving plane, and it tends to roll down the plane following its angle. Sand way above will tend to fall down by its weight to fill up the loosen space.
Is it not something similar to what the video posted by Rocket Magnet shows happens with the air?
Notice that the air against the moving bottom surface is accelerated by the airfoil to a velocity smaller than its own velocity through the air. I believe that is natural, if it gets compacted and dragged like the sand of our experiment. Notice that the upwash in front of the airfoil is a result of this.
Also notice that the air against the moving top surface is accelerated by the airfoil to a velocity higher than its own velocity through the air. I believe that is natural, if it gets loosen (or expanded) and slides down like the sand of our experiment. Notice that the downwash behind the airfoil is a result of this.
For normal level flight, our plane is ramping up on the air (not too soft, not too hard) at the same rate that it naturally falls.
The airfoil uses its velocity energy to grab the air and hang from it, while the air gains that energy.
Lnewqban
10-03-2008, 04:51 PM
#232
RE: [Deleted]
.
One parting shot - The concept of lift is neither complex nor difficult to explain.
The fine points and formula needed to develop an airfoil for a specific use - are more difficult to follow -but then they are simply details.
The details - if put forth as the CONCEPT -end up ,oftimes as analogies-comparisons -obscure representations -and too many times as an attempt to display the plethora of obscurata that exists on the subject.
It is very simple - just pressure difference. Done various ways of course but still the same requirement exists.
One parting shot - The concept of lift is neither complex nor difficult to explain.
The fine points and formula needed to develop an airfoil for a specific use - are more difficult to follow -but then they are simply details.
The details - if put forth as the CONCEPT -end up ,oftimes as analogies-comparisons -obscure representations -and too many times as an attempt to display the plethora of obscurata that exists on the subject.
It is very simple - just pressure difference. Done various ways of course but still the same requirement exists.
10-03-2008, 05:03 PM
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RE: [Deleted]
Holy flying monkeys. As a physicist by training, this thread is one of the most jacked up and utterly amusing reads I’ve had in a while. Glad to see there were some good links toward the end that will help the uninitiated to absorb the science. Thanks for the entertainment!
10-04-2008, 02:26 AM
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RE: [Deleted]
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
If a plane weights 150,000 lbs, for the plane to maintain altitude, there must be an equal upward force opposite gravity delivered by the air to compensate. This means 150,000lbs of upward force provided by the surrounding air (assuming we are getting not vertical thrust component from thrust.) It must, any less and the plane descends.
As for the lift, take simple level flight, ultimately we must create a force opposite to gravity equaling the 150,000lbs of plane. Force = mass x acceleration. This means the mass of effected air must be displaced downward at an acceleration that equals the 150,000lbs of force. In other words, the air is accelerated downward, i.e. downwash. Some of the effects (or process) of crating this downwash are a lower pressure on the top side of the wing compared to the bottom.
This brings us to the Ops complaint about the sides of the wing. We need the create downwash. In doing this, the area above the wing generally sees a larger pressure change (compared to ambient) than the bottom, so in that respect some may say the area above the wing has more air mass being accelerated than the bottom side, hence seems as if that side of the wing is more responsible for generating lift. But the lower pressure on the top side means nothing without reference to the higher pressure on the bottom side. So which side is responsible for the lift? The point is, without a top AND bottom there is no lift. I challenge anyone to make an airfoil without a bottom. Can't be done... it would poof out of existence in our universe.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
If a plane weights 150,000 lbs, for the plane to maintain altitude, there must be an equal upward force opposite gravity delivered by the air to compensate. This means 150,000lbs of upward force provided by the surrounding air (assuming we are getting not vertical thrust component from thrust.) It must, any less and the plane descends.
As for the lift, take simple level flight, ultimately we must create a force opposite to gravity equaling the 150,000lbs of plane. Force = mass x acceleration. This means the mass of effected air must be displaced downward at an acceleration that equals the 150,000lbs of force. In other words, the air is accelerated downward, i.e. downwash. Some of the effects (or process) of crating this downwash are a lower pressure on the top side of the wing compared to the bottom.
This brings us to the Ops complaint about the sides of the wing. We need the create downwash. In doing this, the area above the wing generally sees a larger pressure change (compared to ambient) than the bottom, so in that respect some may say the area above the wing has more air mass being accelerated than the bottom side, hence seems as if that side of the wing is more responsible for generating lift. But the lower pressure on the top side means nothing without reference to the higher pressure on the bottom side. So which side is responsible for the lift? The point is, without a top AND bottom there is no lift. I challenge anyone to make an airfoil without a bottom. Can't be done... it would poof out of existence in our universe.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
10-04-2008, 06:58 AM
#236
RE: [Deleted]
ORIGINAL: JohnW
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
you can't have one without the other .
You ask for Frick- you will also get Frak
They go together .
10-04-2008, 07:31 AM
#238
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RE: [Deleted]
ORIGINAL: Rocketmagnet
Yes you can. You can have drag without lift.
Hugo
you can't have one without the other.
Hugo
The upper side of the wing is important, especially if you wish to optimise its efficiency.
You might have noticed that military aircraft's weaponry is always located underside, as they don’t want to disturb the airflow over the wing.
That's true, lift is due to a pressure difference between upper side and underside of the wing, but how is that pressure difference created?
Well, the wings hit the air accelerating it downwards, creating downwash, just like the helicopter blades do, or just like a propeller but in this case the air is accelerated backwards creating propwash…
[8D]
10-04-2008, 10:38 AM
#239
RE: [Deleted]
ORIGINAL: Rocketmagnet
Yes you can. You can have drag without lift.
Hugo
you can't have one without the other.
Hugo
You guys need to fly more and contemplate less-
10-04-2008, 11:42 AM
#240
Senior Member
RE: [Deleted]
ORIGINAL: dick Hanson
Eggzactly- and the " drag is lift" was meant to be funny- one of natures jokes .
you can't have one without the other .
You ask for Frick- you will also get Frak
They go together .
ORIGINAL: JohnW
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
you can't have one without the other .
You ask for Frick- you will also get Frak
They go together .
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
10-04-2008, 12:18 PM
#241
RE: [Deleted]
Holy flying monkeys. As a physicist by training, this thread is one of the most jacked up and utterly amusing reads I’ve had in a while. Glad to see there were some good links toward the end that will help the uninitiated to absorb the science. Thanks for the entertainment!
You guys need to fly more and contemplate less-
“To invent an airplane is nothing. To build one is something. But to fly is everything.†Otto Lilienthal (1848 – 1896)
Last evening, while flying in a strong wind, I could not avoid imagining how air was flowing above and below the wings of my model airplane, the pressure differencial, etc., just like it has been discussed in this forum.
I believe these concepts enrich the designing, building and flying experiences.
Some pilots don't know, and never will reach their full potential, because they do not ask, read or fly enough.
Inquisitive people ultimately become better designers, builders and pilots,............. just for the fun of flying!
10-04-2008, 01:15 PM
#242
RE: [Deleted]
ORIGINAL: Tall Paul
.
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
ORIGINAL: dick Hanson
Eggzactly- and the " drag is lift" was meant to be funny- one of natures jokes .
you can't have one without the other .
You ask for Frick- you will also get Frak
They go together .
ORIGINAL: JohnW
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
A clear explanation… heh, I doubt I can top some of the posts here, but I’ll put my mark in.
We are dealing with a macro system, i.e. Newton’s laws rule, period. For every force there is an equal and opposite force. Break it down to whatever sub effects you want, but ultimately it all comes back to Newton.
Lift is a force, it is a vector, it does not choose sides. And the whole drag = lift bit... very funny, your vectors are skewed.
you can't have one without the other .
You ask for Frick- you will also get Frak
They go together .
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
It is a momentary condition. and desireable for max vertical acceleration.
I understand all that -
In flight where the wing is used for support- or some maneuvering, there is always lift n drag . and they change places as they go
In some slow speed stuf I have the wing completely stalled by the classic definitionsbut it is still very useful.
When acting as a wing- (support device) - lift and drag are there
when acting as a maneuvering vane - ditto.
when the craft is in "ballistic "mode (fully unloaded ) - of course - drag only AND that is only parasitic drag NOT induced drag
right?
If yo could keep that up - then no wings would be required-
10-04-2008, 01:46 PM
#243
Senior Member
RE: [Deleted]
ORIGINAL: Tall Paul
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
And an airfoil that has stalled doesn't suddenly lose all it's lift. It's simply reached a critical condition that scientists chose to identify with a term. The wing has simply stopped creating more lift with increased AOA and starts creating less and less. And drag keeps right on keeping on...........
Actually, the definition of the stall is probably as good an "airplane on a treadmill" topic as this "which side of the wing" discussion is.
10-04-2008, 01:49 PM
#244
Senior Member
RE: [Deleted]
So............
There are many situations where you have drag without lift. The simple definition of parasitic drag.............. Interference drag............. (Proof in itself that terminology is being discussed as opposed to concepts.)
But show an example where you have lift without drag. And include the definition of induced drag in the explanation.
There are many situations where you have drag without lift. The simple definition of parasitic drag.............. Interference drag............. (Proof in itself that terminology is being discussed as opposed to concepts.)
But show an example where you have lift without drag. And include the definition of induced drag in the explanation.
10-04-2008, 02:32 PM
#246
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RE: [Deleted]
Did anyone see the Mythbusters episode where they trashed the airplane on a treadmill nonsense? They were talking to a real pilot who said he thought that the plane wouldn't take off! It's amazing how someone can be good at flying a plane, but have very little understanding of aerodynamics.
Hugo
Hugo
10-04-2008, 06:41 PM
#247
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RE: [Deleted]
ORIGINAL: da Rock
Yeah, but I'm pretty sure you know that zero G is not logically linked to zero lift. Did you mean something else with that analogy? Because steering an airplane into a direction that gives zero G doesn't mean anything at all about what the wing is seeing for it's AOA. That's a baffling "example" you got there?
.....
ORIGINAL: Tall Paul
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
.....
Unless that zero lift angle is what you reffered to.
Oddly enough higher camber sections produce less drag at slightly higher Cl's than they do at the Cl=0 setting.
10-04-2008, 08:34 PM
#248
Senior Member
RE: [Deleted]
ORIGINAL: BMatthews
I'm not so sure there da Rock. If the pilot is seeing zero G then the aircraft is not generating lift to counter the downward acceleration of gravity. Now that zero lift can come from pushing over into a dive or nosing up and then arcing over such that there's zero G and at that point the plane is in a purely ballistic mode. At that point the wings aren't lifting in either direction which means that they are flying at their zero lift angle and when that happens the Cl is equal to zero and the angle of attack will be at the zero lift angle of attack.
Unless that zero lift angle is what you reffered to.
Oddly enough higher camber sections produce less drag at slightly higher Cl's than they do at the Cl=0 setting.
ORIGINAL: da Rock
Yeah, but I'm pretty sure you know that zero G is not logically linked to zero lift. Did you mean something else with that analogy? Because steering an airplane into a direction that gives zero G doesn't mean anything at all about what the wing is seeing for it's AOA. That's a baffling "example" you got there?
.....
ORIGINAL: Tall Paul
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
When Cl goes to zero, the lift goes away.
The drag doesn't.
In air combat, the pilots "unload" their planes to accelerate, by pushing to zero 'g'.
.....
Unless that zero lift angle is what you reffered to.
Oddly enough higher camber sections produce less drag at slightly higher Cl's than they do at the Cl=0 setting.
The parts that generate lift have no idea what Gs and centrifugal forces there are on the airframe. And they generate lift according to the basics, the speed of the airplane, the AOA of the wing, etc. With any airplane you can arc the sucker over and get an amazing range of numbers on the G-meter (it there is one on the panel) and the wing will continue merrily doing whatever it's airspeed, AOA, and profile are going to do regardless of the reading on the g-meter.
When an airplane sees zero g-s it just happens to be pushing over exactly what's needed for the centrifugal force on the airplane to equal gravity in a direction perfectly opposite gravity. Actually, only the vector of centrifugal force the airplane is feeling that is perfectly opposite gravity has to equal it. The airplane could be experiencing more and probably is. Think about skidding a turn. Sort of the same concept.
10-04-2008, 08:58 PM
#249
Senior Member
RE: [Deleted]
The fighter jet accelerates better at "zero G" simply because the wing is benefitting by whatever the pilot is doing that has the airplane on a path that's got the g-meter thinking zero g's.
I guess you could say that whenever you're reading zero G, don't bet that gravity isn't working on the mass. But bet that at least two conflicting forces are, and they're cancelling out. But the wing and tail are still at work at least directing the path of the airplane. And how do they do that? With "the force".
whatever...........
Just another semi-antics deal...........
I guess you could say that whenever you're reading zero G, don't bet that gravity isn't working on the mass. But bet that at least two conflicting forces are, and they're cancelling out. But the wing and tail are still at work at least directing the path of the airplane. And how do they do that? With "the force".
whatever...........
Just another semi-antics deal...........
10-04-2008, 09:37 PM
#250
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RE: [Deleted]
I have a question about flaps.
I think someone brought up flaps earlier and said it was a can of worms, but just a quick question.
When the flaps are down, is air really following the top of the wing, down the flap to cause a low pressure, or is it just the displacement of air below it causing a general low pressure above the flap?
I'm sure there's some major high pressure going on under the wing in this condition, but I was thinking that there's no way that air is following along the top surface of the wing, then down the flap. It's gota be 'stalled' there right?
http://www.youtube.com/watch?v=XKuwJ...eature=related
I think someone brought up flaps earlier and said it was a can of worms, but just a quick question.
When the flaps are down, is air really following the top of the wing, down the flap to cause a low pressure, or is it just the displacement of air below it causing a general low pressure above the flap?
I'm sure there's some major high pressure going on under the wing in this condition, but I was thinking that there's no way that air is following along the top surface of the wing, then down the flap. It's gota be 'stalled' there right?
http://www.youtube.com/watch?v=XKuwJ...eature=related
