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Thread: Who Likes Aircraft?

  1. #121
    Join Date: Feb 2017

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    All the wind tunnel tests I've watched show smoked air going around a wing, and you can clearly see it's faster on the top surface. Breaking up as the wing angle of attack becomes excessive, which is what the stall is, and why you get stall buffet when flying light aircraft. The air hits the tailplane and causes this buffet.

    I respect others views and am not putting people down, but would love to understand how you think Bernoulli is wrong or 'venturi' effects cause the effects.

    Bernoullis principle also not only explains lift over a wing but the effects of high and low pressure on either side of a control surface. So when the right aileron goes up, the static pressure is increased by virtue of the aieleron slowing the air over the top surface by moving up. The opposite on the left wing, with the left aileron going down, causes the differential lift and hence banking to the right. The same happens with the elevators and rudder in the pitching and yawing planes. Also Bernoulli accounts why if air hits the tail plane and moves the tailplane to the right, it's right surface has a higher static pressure because the big keel surface of the tail plane presented to the air flow, slows the air down. The pressure difference to the left side of the tailplane means the tailplane moves back in line. The same thing happens with the elevators and a dihedral wing, but concorde had a anhedral wing and no elevators or horizontal stabiliser.

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  2. #122
    Join Date: Dec 2008

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    A wing is curved on the top surface thus giving the air over that surface further to travel. This makes that air slower and so decreases the pressure atop the wing creating a partial vacuum. This is the cause of the lift experienced by that aerofoil.
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  3. #123
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    Quote Originally Posted by Haselsh1 View Post
    A wing is curved on the top surface thus giving the air over that surface further to travel. This makes that air slower and so decreases the pressure atop the wing creating a partial vacuum. This is the cause of the lift experienced by that aerofoil.
    I think though it has to be explained by the effect on a surface doesn't it?, which is what is said when referring to static pressure ie the pressure on a surface. Air can't have a different static pressure by virtue of moving slower or faster, it can have different energy, since static pressure does refer to the effect on a surface.

    Also you can have a symmetrical aerofoil (curved equally on top to bottom) generate lift by its incidence to the fuselage. This is what aerobatic aircraft like extras and sukhois use but I agree with the sentiment of your point which is effectively to do this in a different way using incidence. That's what Concorde was effectively doing when landing. However the air actually moves faster over the top surface whisking away away those air molecules to exert a pressure on the wing upper surface hence reducing static pressure on the upper wing surface.

  4. #124
    Join Date: Dec 2008

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    The air on the top of a wing cannot move faster than that below as it has farther to travel. This is what results in the low pressure that results in lift. This is basic GCSE physics.
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  5. #125
    Join Date: May 2012

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    I don't think you remember you GCSE very well, and I do not agree with you.

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  6. #126
    Join Date: Feb 2013

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    Quote Originally Posted by CageyH View Post
    I don't think you remember you GCSE very well, and I do not agree with you.

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    Hey, i was right lol
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  7. #127
    Join Date: Feb 2017

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    Quote Originally Posted by struth View Post
    Hey, i was right lol
    Yes because the curved top surface is longer than the flater under surface, so the air is accelerated. When the airstream meets the wing leading edge some of it goes over the top and the rest under the wing, but it must meet at the trailing edge at the same point - this is part of fluid or air dynamics. As the top surface is longer the air must have travelled faster for the same time it got from the leading edge to trailing edge for air going under the wing.

    But if it's to do with wing incidence in a aerobatic aerofoil which often has a symmetrical wing (same curve on top as on bottom), the wing must be angled up at the airflow where it's fitted to the fuselage, to create the acceleration of air over the top. If it wasn't angled up the air over the top and bottom would travel the same speed, there would be no static pressure differences, and the wing would not generate lift.

  8. #128
    Join Date: Mar 2008

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    I'm inthescottishmafia.

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    No, the air is not accelerated. It is forced downwards towards the trailing edge of the aerofoil, creating a lower pressure, due to the angle of attack of the wing, this also means the air is compressed below the wing, giving higher pressure. This is what creates lift, NOT faster airflow over the top of the wing.
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  9. #129
    Join Date: Feb 2017

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    Quote Originally Posted by Ali Tait View Post
    No, the air is not accelerated. It is forced downwards towards the trailing edge of the aerofoil, creating a lower pressure, due to the angle of attack of the wing, this also means the air is compressed below the wing, giving higher pressure. This is what creates lift, NOT faster airflow over the top of the wing.

    It is accelerated because it must get to to same point at the trailing edge as the air going underneath. It's forced downwards yes, as the aerofoil surface angles away downwards on the top of the wing.

    A conventional aerofoil wing shape doesn't have to be at an angle of attack to the airflow to create lift though. Angle of attack is simply the angle of the wing to the airflow. If the wing is flat with the airflow, lift will happen as airflow speed increases, otherwise an aircraft with a wing with limited incidence to the fuselage would not generate lift. I've made radio control model aeroplanes with no wing incidence (to create an angle of attack in level fligh) but they fly with the throttle in the same position and maintain height. This is just lift over the wing at a certain speed with the wing at no angle of attack to the airflow.

    Compression of air doesn't explain static pressure acting on a surface and by bernoullis theory that the faster it travels the less static pressure can occur. My point is it's this differential between static pressure on the upper and lower surfaces which creates an upward lifting force.

  10. #130
    Join Date: Feb 2017

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    Quote Originally Posted by Ali Tait View Post
    No, the air is not accelerated. It is forced downwards towards the trailing edge of the aerofoil, creating a lower pressure, due to the angle of attack of the wing, this also means the air is compressed below the wing, giving higher pressure. This is what creates lift, NOT faster airflow over the top of the wing.

    It is accelerated because it must get to to same point at the trailing edge as the air going underneath. It's forced downwards yes, as the aerofoil surface angles away downwards on the top of the wing.

    A conventional aerofoil wing shape doesn't have to be at an angle of attack to the airflow to create lift though. Angle of attack is simply the angle of the wing to the airflow. If the wing is flat with the airflow, lift will happen as airflow speed increases, otherwise an aircraft with a wing with limited incidence to the fuselage would not generate lift. I've made radio control model aeroplanes with no wing incidence (to create an angle of attack in level fligh) but they fly with the throttle in the same position and maintain height. This is just lift over the wing at a certain speed with the wing at no angle of attack to the airflow.

    Compression of air doesn't explain static pressure acting on a surface and by bernoullis theory that the faster it travels the less static pressure can occur. My point is it's this differential between static pressure on the upper and lower surfaces which creates an upward lifting force.

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