Thread: Discussion NASA says lift from air shoved down - can we trust NASA? View Single Post
Nov 13, 2011, 06:40 PM
Registered User
Canada, AB, Red Deer
Joined Apr 2010
315 Posts
Hi Tim, I will be nice this time...I promise Please, for the sake of the discussion, rather than completely shutting everything off, open your mind a bit to the whole picture. Never once did we disagree with you about it being shoved down, we all agreed that does take place, but there is a lot more to it than that.

For Example, since you like NASA links, here is one from the same guys as your link that say downwash reduces lift, rather than causes it.
http://www.grc.nasa.gov/WWW/k-12/airplane/downwash.html
Cut-n-paste from this link
"The wing tip vortices produce a downwash of air behind the wing which is very strong near the wing tips and decreases toward the wing root. The local angle of attack of the wing is increased by the flow induced by the downwash, giving an additional, downstream-facing, component to the aerodynamic force acting over the entire wing. The downstream component of the force is called induced drag because it faces downstream and has been "induced" by the action of the tip vortices. The lift near the wing tips is defined to be perpendicular to the local flow. The local flow is at a greater angle of attack than the free stream flow because of the induced flow. Resolving the tip lift back to the free stream reference produces a reduction in the lift coefficient of the entire wing".

This one is neat, also from your same source. This one is called The Lift Equation, and what do you know, this "official" NASA lift equation has not just the velocity of the air, but it also takes into account the dynamic pressure, and it says that that portion of the equation is taken from Bernoulli's equation...wow!!
http://www.grc.nasa.gov/WWW/k-12/airplane/lifteq.html
Cut-n-paste from that link:
In the equation given above, the density is designated by the letter "r." We do not use "d" for density, since "d" is often used to specify distance. In many textbooks on aerodynamics, the density is given by the Greek symbol "rho" (Greek for "r"). The combination of terms "density times the square of the velocity divided by two" is called the dynamic pressure and appears in Bernoulli's pressure equation.

And here is yet another one from your very same source, which explains hw both the pressure difference/Bernoulli theory and turning flow/Newton theory are BOTH correct, if applied correctly.
the quote:
"So both "Bernoulli" and "Newton" are correct. Integrating the effects of either the pressure or the velocity determines the aerodynamic force on an object. We can use equations developed by each of them to determine the magnitude and direction of the aerodynamic force. "