When discussing the force of lift in airfoil, we say that molecules come to upper and lower sides of the airfoil must reach each other to the end of airfoil, due to the longer distance of the airfoil's upper side compare to lower side, molecule velocity at the upper side is higher, according to Bernoulli's equation pressure at upper side is less than lower side. My question is, why do molecules reach the end at the same time? Could this be due to the conservation and continuity of mass?
Dear Kourosh
As mentioned by dear Dr.Sadegh, some explanations are available. In the aforementioned theory, the molecules must meet each other due to conservation of mass. However, the
needed forces for changing flow direction is another good explanation.
This is a widespread misunderstanding of Bernoulli's eqation. Ask yourself how the lift force is generated when the air foil is as thin as paper. It has nothing to do with longer path of molecules
Dear dr Farhad Sadegh Moghanlou , Mohammad Vajdi
Can you help me about this subject?
Dear Jan Wilgenhof
If this subject has not to do with the longer path of molecules, so what is the reason for the difference in pressure at the top and bottom sides of the airfoil?
Dear Kourosh Vaferi ,
The reason you mentioned about the lift force of airfoils, is the simplest justification for airfoils function. There have been some theories about the increased velocity at upper side of airfoil which is too tedious to be written here. Please have a look on following link, i think it will help you:
https://en.wikipedia.org/wiki/Lift_(force)
Dear Kourosh
As mentioned by dear Dr.Sadegh, some explanations are available. In the aforementioned theory, the molecules must meet each other due to conservation of mass. However, the
needed forces for changing flow direction is another good explanation.
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