Lift Produced Where Wing Transects Fuselage
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Lift Produced Where Wing Transects Fuselage
I don't know exactly what you call this, but I remember hearing that to some extent the area between the left and right wing "counts" for producing lift
Last edited by Jane-DoH; 22nd Jul 2011 at 04:02.
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Wingbox is a structural term.
I'm not sure there is a specific aerodynamic term for what you describe - wing-body lift would include all of the wing contribution, not just the 'carry through' term. The wing does get some benefit (or decrement, if you considered an isolated wing) from being on a fuselage (or vice versa if you prefer) but the theoretical wing planform in the fuselage is purely that - theoretical.
I'm not sure there is a specific aerodynamic term for what you describe - wing-body lift would include all of the wing contribution, not just the 'carry through' term. The wing does get some benefit (or decrement, if you considered an isolated wing) from being on a fuselage (or vice versa if you prefer) but the theoretical wing planform in the fuselage is purely that - theoretical.
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Mad (Flt) Scientist
So wing-body lift includes both the lift of the wing and the part that is "in the fuselage"?
What variables increase this benefit? I assume a fuselage that was flattened where the wing intersects it, had wing-body fairings to blend it together and/or it's intakes were flatter than deep (if they were in the wing-root) would have better overall wing-body lift?
I'm not sure there is a specific aerodynamic term for what you describe - wing-body lift would include all of the wing contribution, not just the 'carry through' term.
The wing does get some benefit (or decrement, if you considered an isolated wing) from being on a fuselage (or vice versa if you prefer) but the theoretical wing planform in the fuselage is purely that - theoretical.
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have a look at this nice picture, it shows, through condensation, the distribution of lift on an airplane during a high-g maneuver
it is from:
A Physical Description of Lift
and the lift over the fuselage in this case looks not like in some more teoretical pictures with lift over the fuselage
it is from:
A Physical Description of Lift
and the lift over the fuselage in this case looks not like in some more teoretical pictures with lift over the fuselage
In my naive wing model, it goes like this:
The extant fuselage length, trailing behing the wing box, interferes with the development of lift vorteces from this part of the wing. No vortex, no lift.
Lifting body would not be a counter-example because in that topology, the fuselage is not really trailing. The lengths are balanced.
(Definitely waiting to be corrected - I'm still mentally struggling with the role of viscosity - I know it's essential)
The extant fuselage length, trailing behing the wing box, interferes with the development of lift vorteces from this part of the wing. No vortex, no lift.
Lifting body would not be a counter-example because in that topology, the fuselage is not really trailing. The lengths are balanced.
(Definitely waiting to be corrected - I'm still mentally struggling with the role of viscosity - I know it's essential)
Last edited by balsa model; 22nd Jul 2011 at 14:40. Reason: spelling
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Hi Jane-doh
Hope you are safe. I was about to bring up 'lifting body', parasite fighter, and 'gremlin'.
Many folks disapprove of lifting body, NASA liked it well enough to base the Shuttle on it.
Problem? Intuitively, and visually, things that don't look like wings make Bernoullians anxious.
Newton. Deflected energy can "lift". Simples. Bernoulli was a Swiss 'plumber'.
Hope you are safe. I was about to bring up 'lifting body', parasite fighter, and 'gremlin'.
Many folks disapprove of lifting body, NASA liked it well enough to base the Shuttle on it.
Problem? Intuitively, and visually, things that don't look like wings make Bernoullians anxious.
Newton. Deflected energy can "lift". Simples. Bernoulli was a Swiss 'plumber'.
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@Jane-Doh
No. Wing-body is the term we use at my current (and indeed former) employer to mean the total lift of both wing and body, but excluding the tailplane contribution. Taill-off is commonly tested in wind tunnel development so it's useful to have a term for that condition. It therefore includes the TOTAL fuselage contribution.
Generally, wing/body interface design, at least in the commercial world, is concerned more to address drag than lift. If you need more lift its generally better to add more wing than to make the fuselage lift more - the fuselage is a poor lifting device. Obviously the fuselage does generate some lift, and you wouldn't want to throw it away, but it's not a design criteria usually.
@grity
Interesting pic, but be careful of assuming that the low pressure region is directly proportional to lift. The fuselage is relatively long chord, so a much lower pressure drop will, integrated over the longer "chord", create proportionately more lift. But, yes, the diagram of the SEP is over simplified - usually a fuselage degrades lift compared to the isolated wing.
So wing-body lift includes both the lift of the wing and the part that is "in the fuselage"?
What variables increase this benefit? I assume a fuselage that was flattened where the wing intersects it, had wing-body fairings to blend it together and/or it's intakes were flatter than deep (if they were in the wing-root) would have better overall wing-body lift?
@grity
Interesting pic, but be careful of assuming that the low pressure region is directly proportional to lift. The fuselage is relatively long chord, so a much lower pressure drop will, integrated over the longer "chord", create proportionately more lift. But, yes, the diagram of the SEP is over simplified - usually a fuselage degrades lift compared to the isolated wing.
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Interesting historical trivia:
Benny Howard's DGA-8 through DGA-12 SE 4-place cabin aircraft were 38' span high-wing monoplanes. The wing area was quoted as 185 sq. ft.
Then the DGA-15 was derived from the earlier ships. Same 38' span, same chord, but now the area was quoted as 210 sq. ft.
I have determined that the difference of 25 sq. ft. corresponds to the "wing box" area - the wing chord times the fuselage width. So the difference is simply a difference in method of calculation.
Benny Howard's DGA-8 through DGA-12 SE 4-place cabin aircraft were 38' span high-wing monoplanes. The wing area was quoted as 185 sq. ft.
Then the DGA-15 was derived from the earlier ships. Same 38' span, same chord, but now the area was quoted as 210 sq. ft.
I have determined that the difference of 25 sq. ft. corresponds to the "wing box" area - the wing chord times the fuselage width. So the difference is simply a difference in method of calculation.
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Interesting pic, but be careful of assuming that the low pressure region is directly proportional to lift. The fuselage is relatively long chord, so a much lower pressure drop will, integrated over the longer "chord", create proportionately more lift. But, yes, the diagram of the SEP is over simplified - usually a fuselage degrades lift compared to the isolated wing.
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Jane...
My experience in these design parameters is in the subsurface realm, but the principles of air being thin water should apply.
Bernoulli's principle is generally explained by the argument that the faster speed of the air along the top of the wing leads to reduced air pressure above and hence produces a lift.
Given this, simplistically, one would rationally surmise that the fuselage negates this basic couple.
If we look at Bernoulli's Laws, or what is the common explanation of wing aerodynamics. Airfoils are curved on top and flat below, and therefore the air follows a longer path above than below. Since the upper surface of the wing is longer, it causes the upper air to flow faster than the lower, which (by Bernoulli's principle) creates lower pressure above. According to this pure principle, a wing can create lift at zero attack angle, and do not deflect air, the air behind the wing is flowing the same as the air ahead. Are there any real time examples of the wing section at zero angle providing lift?
We have all seen the diagrams, with the airflow coming together nicely at the back of the wing, in a straight line with the air from below.
To add further issue, given what we have seen in wake vortex creation, does that seem plausible?
Then again,
If we look at Newtons Laws, using principles of Newtonian Angle, wings are forced upwards because they are tilted and they deflect air. The air behind the wing is flowing downwards, while the air far ahead of the wing is not. Both the upper and lower surfaces of the wing act to deflect the air. (which would answer your question regarding the surface between the wings creating lift) The upper surface deflects air downwards because the airflow "sticks" to the wing surface and follows the tilted wing, called the "Coanda Effect" (marine thrusters and ducted fan UAV's). (note: while flaps radically effect lift, they add no surface length over the wing, this appears counter to Bernoulli)
For this to be applicable, air's inertia is critical, so after the wing has passed by, air must remain flowing downwards...sound familiar, ie wake vortex creation?
Given that....
Newton and Bernoulli do not contradict each other. Newton's Laws based on air deflection explain 100% of the lifting force. Bernoulli's Laws based on air velocity also explain 100% of the lifting force.
Hope this helps.
I will be appearing here from 9 to 10 Monday thru Friday, please tip your servers....
My experience in these design parameters is in the subsurface realm, but the principles of air being thin water should apply.
Bernoulli's principle is generally explained by the argument that the faster speed of the air along the top of the wing leads to reduced air pressure above and hence produces a lift.
Given this, simplistically, one would rationally surmise that the fuselage negates this basic couple.
If we look at Bernoulli's Laws, or what is the common explanation of wing aerodynamics. Airfoils are curved on top and flat below, and therefore the air follows a longer path above than below. Since the upper surface of the wing is longer, it causes the upper air to flow faster than the lower, which (by Bernoulli's principle) creates lower pressure above. According to this pure principle, a wing can create lift at zero attack angle, and do not deflect air, the air behind the wing is flowing the same as the air ahead. Are there any real time examples of the wing section at zero angle providing lift?
We have all seen the diagrams, with the airflow coming together nicely at the back of the wing, in a straight line with the air from below.
Then again,
If we look at Newtons Laws, using principles of Newtonian Angle, wings are forced upwards because they are tilted and they deflect air. The air behind the wing is flowing downwards, while the air far ahead of the wing is not. Both the upper and lower surfaces of the wing act to deflect the air. (which would answer your question regarding the surface between the wings creating lift) The upper surface deflects air downwards because the airflow "sticks" to the wing surface and follows the tilted wing, called the "Coanda Effect" (marine thrusters and ducted fan UAV's). (note: while flaps radically effect lift, they add no surface length over the wing, this appears counter to Bernoulli)
For this to be applicable, air's inertia is critical, so after the wing has passed by, air must remain flowing downwards...sound familiar, ie wake vortex creation?
Given that....
Newton and Bernoulli do not contradict each other. Newton's Laws based on air deflection explain 100% of the lifting force. Bernoulli's Laws based on air velocity also explain 100% of the lifting force.
Hope this helps.
I will be appearing here from 9 to 10 Monday thru Friday, please tip your servers....
Last edited by FlightPathOBN; 26th Jul 2011 at 00:59.
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grity
That's an F-14. As I understand it, the pancake produces the most lift at high alphas, at supersonic speeds with the wing swept back...
What if the wing's in the middle of the fuselage?
bearfoil
Gremlin?
Well, the laws of physics are what they are regardless of what you believe them to be. If I believe the sky's green and it's blue, my belief doesn't change the sky's color; the sky's blue.
Mad (Flt) Scientist
The tailplane reduces overall lift doesn't it?
So the term "tail off" includes total fuselage contribution to lift? I assume it doesn't include the tail... (Not to sound stupid, but I want to know if I'm wrong).
have a look at this nice picture, it shows, through condensation, the distribution of lift on an airplane during a high-g maneuver
and the lift over the fuselage in this case looks not like in some more teoretical pictures with lift over the fuselage
bearfoil
Hope you are safe. I was about to bring up 'lifting body', parasite fighter, and 'gremlin'.
Many folks disapprove of lifting body, NASA liked it well enough to base the Shuttle on it.
Problem? Intuitively, and visually, things that don't look like wings make Bernoullians anxious.
Problem? Intuitively, and visually, things that don't look like wings make Bernoullians anxious.
Mad (Flt) Scientist
No. Wing-body is the term we use at my current (and indeed former) employer to mean the total lift of both wing and body, but excluding the tailplane contribution.
Taill-off is commonly tested in wind tunnel development so it's useful to have a term for that condition. It therefore includes the TOTAL fuselage contribution.
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If I may cut in ...
The distribution of lift across the span from fuselage centreline to wing tip on a typical subsonic airplane looks like this:
">
The bit over the fuselage is usually described as 'wing/body carryover' It comes about because the airflow cannot tolerate a sudden drop in pressure where the wing root flow 'passes by' the fuselage so there is a 'smearing' of the pressure through a spanwise pressure gradient. Where the LH gradient meets the RH gradient pressures are equal.
You can have any definition you like for wing reference area so long as you stick to it. Some use a line across the fuselage joining the two wing root LE points (and/or TE root) others use the projection of LE and TE through to the centreline.
Wing body lift is just that - wing plus body without tail or nacelles. Just a remark that at normal civil aircraft AoAs, even up to stall, the fuselage lift per se is pretty small, although there is lift in the wing region as above.
That picture of the F14 is showing condensation in the wing vortices. This is associated with the drop in static pressure in those vortices. The drop is biggest at the centre of the vortex so the 'outer' boundary is just a region where the pressure has not dropped enough to cause condensation - it doesn't mean that there is no lift from the aircraft surface underneath that point.
The distribution of lift across the span from fuselage centreline to wing tip on a typical subsonic airplane looks like this:
">The bit over the fuselage is usually described as 'wing/body carryover' It comes about because the airflow cannot tolerate a sudden drop in pressure where the wing root flow 'passes by' the fuselage so there is a 'smearing' of the pressure through a spanwise pressure gradient. Where the LH gradient meets the RH gradient pressures are equal.
You can have any definition you like for wing reference area so long as you stick to it. Some use a line across the fuselage joining the two wing root LE points (and/or TE root) others use the projection of LE and TE through to the centreline.
Wing body lift is just that - wing plus body without tail or nacelles. Just a remark that at normal civil aircraft AoAs, even up to stall, the fuselage lift per se is pretty small, although there is lift in the wing region as above.
That picture of the F14 is showing condensation in the wing vortices. This is associated with the drop in static pressure in those vortices. The drop is biggest at the centre of the vortex so the 'outer' boundary is just a region where the pressure has not dropped enough to cause condensation - it doesn't mean that there is no lift from the aircraft surface underneath that point.
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bearfoil
Well, the sky's coloring is kind of a bluish color in day-time with some white and gray (clouds) and yellow if you're looking at the sun, very dark blue to black at night excepting the stars, various shades of red, orange, pink and so forth during sunset.
The point is that no matter what you believe the color to be, the sky is a given color in a given location. These colors can be measured in terms of wavelength.
R.C.
"That being said, I'd like to remind everybody in a manner reminiscent of the SNL bit on Julian Assange, that no matter how I die: It was murder (even if there was a suicide note or a video of me peacefully dying in my sleep), and should I be arrested or framed for a criminal offense, or disappear entirely -- I think we all know who to blame for it"
Well, the sky's coloring is kind of a bluish color in day-time with some white and gray (clouds) and yellow if you're looking at the sun, very dark blue to black at night excepting the stars, various shades of red, orange, pink and so forth during sunset.
The point is that no matter what you believe the color to be, the sky is a given color in a given location. These colors can be measured in terms of wavelength.
R.C.
"That being said, I'd like to remind everybody in a manner reminiscent of the SNL bit on Julian Assange, that no matter how I die: It was murder (even if there was a suicide note or a video of me peacefully dying in my sleep), and should I be arrested or framed for a criminal offense, or disappear entirely -- I think we all know who to blame for it"