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Thread: Theory on lift
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Old 19th Oct 2012, 20:52
  #169 (permalink)  
henra
 
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Originally Posted by italia458
Air has to get deflected to create 'lift'. If air is not deflected by the airfoil, there is no net force and therefore, no lift.
I take it you are a 'Newtonian'

But if we assume we have high pressure on the lower side and low pressure on the upper side I fail to see why simple physics shouldn't apply:
F=p*A, p being the pressure differential and A the wing area.

...if there is a low pressure, the air will flow in the direction of the low pressure - which is upwards. If the air flows upwards, according to Newton's 3rd law, there will be an equal and opposite down force on the wing. That's the opposite to lift!
One word: Inertia.
Somewhere on the first pages of this thread I commented on how Bernoulli and Newton are somewhat linked.

That is why, if you have an airfoil where the camber at the TE points downward , the air molecules will continue downward even behind the Trailing Edge. Therefore you have a bigger 'expansion' and thus higher acceleration over the wing, reducing the pressure according to Bernoulli. This same effect gives you a bigger mass stream deflection according to Newton.
In my eyes Bernoulli and Newton are not really conflicting. they are different ways of looking at the same phenomenon, that is causing the lift.
This effect itself must be somehow linked to the behavoíour and interaction of the molecules in the air, because lift requires viscosity and mass.

Last edited by henra; 19th Oct 2012 at 20:54.
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