Airplane lift fly wing fin

[U2U2U2]

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/?utm_source=pocket-newtab

To those that like to compare aircraft wings to fins.
Many references when comparing a fin to wing are made to Daniel Bernoulli, who is mentioned in the link.
FWIW Bernoulli died 1782, Wright Brothers first flight 1903.

[dvCali]

[grantmac017]

Bernoulli has much to do with carburetors, but nothing to do with wings or fins since they aren't a closed system.

[Brian_S]

In an attempt to cure everyone's insomnia, I'll try to explain why I think this article was very misleading.

The equations governing flow of a continuous medium are two: Conservation of Mass, and Conservation of Momentum (a.k.a. the momemtum equation). The momentum equation does include all the physical forces that affect the pressure distribution, and thus lift, on a wing or a fin. You might think of Newton's 2nd Law as a simplification of the momentum equation.

The author did state that there was no disagreement on the equations. However, he then goes into this argument about whether it's Bernoulli's equation or Newton's law which governs the lift on a airfoil. This is where it just adds to the confusion.

The momentum equation is necessarily applied to a region of interest, often called a 'control volume' (CV). It states that the sum of all forces acting on the CV must equal to time rate change of momentum within the CV, plus the net momentum flow out of the CV. If you were to apply the momentum equation to a small region of interest, like a particle with no flow through it, then it would look like the familiar F = Ma that you've seen in physics class - Newton's Law.

(Is anyone still reading?)

If instead you apply the momentum equation to flow along a streamline, in a steady, incompressible flow field, and you neglect viscous effects and interruptions to the streamline, then you have the Bernoulli Equation. So the Bernoulli Equation is just a highly simplified version of the momentum equation.

So, it's not like Newton's laws and the Bernoulli Equation are two different theories - they are simplifications (maybe extreme simplifications, neglecting different aspects) of the same governing principle.

The article made for good reading, but instead of explaining why only a piece of the theory doesn't explain the whole phenomena, he tried to pit two pieces of the same theory against one another - which we've seen in this forum and elsewhere.

(Insert snoring sound.)

[Brian_S]

[U2U2U2]

[cgoudie1]

I would have to disagree. Bernoulli has a lot to do with wings and fins, and propellers, and a host of other physical properties that are developed
as a result of pressure differential from difference in travel distance
in a substance. He's definitely why airplanes fly.

-Craig

[boardsurfr]

Thanks, Brian, great explanation!

[U2U2U2]

Snoring sound. Lol.
The link I posted was in regard to references on Windsurf Forums that our fins are likened to an aircraft wing. I have not seen any discussion , in regard to foils, which because of the horizontal actual wing , instead of verticals are a wing.Duh.
What makes a airplane stay airborne, is the same as when it takes off, when lift overcomes gravity, and thrust overcomes drag.
The air is thinner at higher altitude so more lift and thrust isn’t necessary .
Some Business jets are flying at 410,00 now to take advantage of this, and because the population there is not as heavy , so a more direct course can be flown.

[grantmac017]

Bernoulli's principal is at most a minor contributor to lift compared to the Kutta–Joukowski theorem.