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Production of Lift – aerodynamics explanation needed ASAP !

Asked by: 2079 views Aerodynamics, Commercial Pilot, Flight Instructor, General Aviation, Private Pilot, Student Pilot

Good morning everyone,

I am an avid aerodynmic fan, currently doing my CFI course in Florida.

I have been reviewing the textbook known as 'Aerodynamics for Naval Aviators' and came up with a few questions...

1. First, to begin with, for a wing to produce a lift, we have high pressure below and low pressure above wing and the problem is that the book tries to explain with 'suction pressure' with weird diagram, and labeling them with + and - to show intensity of suction pressure.

2. Secondly, we know that airflow travels faster above the wing than that of below, but I still have not found the decent answer to this question. 

I am looking for the answers other than as follow:-

1)There is sudden change in direction of motion of airflow

2)Airflow above the wing must travel greater distance to meet up at rear stagnation point(proved wrong by NASA) - such a stupid logic; I do not know who made it but..

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2 Answers



  1. Nascr1Arrival on Mar 10, 2016

    Good morning, I think I can answer both questions in one answer. Let’s define some terms first. Let’s start with the pronciple of conservation of energy. We can’t magically lose or add energy into a system, in this case an airstream. The energy of an airstream is in two forms. It has potential energy known as static pressure and kinetic energy known as dynamic pressure. The total pressure of an airstream is the sum of the static and dynamic pressure. So no matter what kind of airfoil the air is flowing over, the total pressure remains constant. So a decrease in static pressure must result in an increase in dynaic pressure. Dynamic pressure is measured in speed. So when an airstream is compressed by an airfoil, the static pressure decreases (the suction), and the speed increases (the faster airflow). I hope that helps.

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  2. Skyfox on Mar 16, 2016

    Bernoulli’s principle, aka. the venturi effect, is a well studied phenomenon of fluid dynamics, which includes the study of the flow of air and other gases over/through/around shapes and surfaces. Based on what was taught to me in aerodynamics class at the university, about 20% of lift is Newtonian (ie. the higher pressure below the wing due to airflow being deflected downwards) and the remaining 80% is Bernoulli/venturi effect (ie. the lower pressure above the wing due to the airflow following the camber of the airfoil). Some will argue that it’s the other way around but it has been proven that an airfoil in a relative wind will generate lift with its curved upper surface even when the lower surface is perfectly parallel to the air flow so it has no air deflection. It seems kind of counter-intuitive that the air above the wing or going through a venturi would have a lower pressure since it is in essence being squeezed by the airfoil being in the way of its motion, but that’s just how it works in physics that the pressure drops. It’s the same in the motion of liquids through a venturi even though liquids can’t be compressed.

    Anyway, the lift generated by the lower pressure, or suction, on top of the wing is more accurately described as the atmospheric pressure inside the wing pushing up against the inner surface of the top of the wing as it tries to fill in that low pressure area above the wing, as well as the higher pressure area under the wing trying to do the same thing.

    Beyond that, I’m not entirely sure what your question is.

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