Question

Bernoulli's principle does not explain why the air flows faster past the top of the wing and slower past the underside of the aerofoil. Do you agree?

Answer 1

No.

Answer 2

no, because when it flows over the wing there is much less resistance as opposed to the opposite.

Answer 3

on the upper part streamlines are denser .so,velocity will be more.

Answer 4

when air flows across an airfoil, the air going over the top separates from the air flowing under the bottom. it then must rejoin at the trailing edge of the airfoil. because the distance over the top is greater than the distance across the bottom, the air going over the top must go faster. the faster the air goes, the less pressure it exerts on the airfoil (bernoulli's principle) therefore the air over the top creates a vacuum relative to the air going across the bottom sucking the airfoil up as the pressure from underneath pushes the airfoil up. keep in mind that bernoulli's principle only works for sub-sonic airspeeds and works the opposite at transonic and supersonic speeds.

Answer 5

Yes. You are correct, and if you realized this on your own accord then good for you. It's true that the higher the velocity of a fluid, the lower the pressure it exerts on the airfoil, but Bernoulli's principle says nothing about why the air would move faster. The common textbook answer, as stated above, is that the wing splits the airstream and it rejoins at the other side, and so because the top of the wing is curved, the air must travel a greater distance in the same amount of time, so it must move faster. This is false. Qualitatively, you might recognize that if this were the case, planes could never fly upside down (they can, of course). More concretely, you could watch the airflow over a wing in a wind tunnel -- the air is indeed split by the wing but it does NOT perfectly rejoin, and so the entire assumption from which you derive the velocity differential is invalid.

Answer 6

no i don't

Answer 7

Jemurray3 is correct, Bernoulli alone is not enough to explain aerodynamic lift. You need to incorporate Newton's 3rd Law as well. Individually either set of equations won't explain lift, but if you put the two together, it works.