Ye Olde Bernoulli vs Newton debate

[PeterNSteinmetz]

Now treated by Scientific American - https://getpocket.com/explore/item/no-one-can-explain-why-planes-stay-in-the-air

The headline shows how far Scientific American has sunk since I was a child.

 

[RandomDroneGuy]

Conceptually, I think Bernoulli makes a lot more sense if one thinks of the upper camber of a conventional wing as half a venturi that creates a partial vacuum. Newton's contribution is to induce rotation around the axes, as well as creating some lift by way of positive angle of incidence. The latter exerts direct force in a downward direction (pushing the wing upwards), but it also increases lift on the upper camber by effectively increasing AoA in straight and level flight.

An airplane could fly using a piece of plywood as a wing with lift entirely provided courtesy of Sir Isaac given positive angle of incidence and sufficient thrust; but it would be very inefficient. The more-efficient approach is to let Bernoulli do his thing in providing most of the lift, and Newton do his in providing control and supplementing lift.

I always considered Bernoulli and Newton to be two friends who get along quite nicely. I think they laugh at researchers who don't understand their friendship.

 

[PeterNSteinmetz]

What I really liked about the article (aside from the title) was that it points out that the basically what is going on this debate is that the real answer is given by fluid dynamics. These two explanations are basically first order approximations to a complex situation. I usually teach that the "Newton" explanation is the better approximation at higher angles of attack and lower speeds, whereas the "Bernoulli" explanation is the better one at higher speeds like cruise. The real answer is some mixture of the two. But you better know the two approximations for the FAA exam!

When I was a child my father explained it using the Bernoulli explanation but I always thought something was a bit fishy because the apparent Newtonian one and the stall is obvious when you hold your hand out the window of the moving car. No matter how carefully I tried to cup my hand into an airfoil shape, I could not get apparent Bernoulli lift to perceptibly dominate.

The thing which always amuses me is as noted in the article - how there are two different camps that will argue vociferously about Bernoulli versus Newton based on practical experiences.

 

[nikita30]

The Ye Olde Bernoulli vs Newton debate is a timeless discourse, akin to the classic struggle between theory and application. Bernoulli's fluid dynamics theory and Newton's laws coexist, each revealing facets of reality. This intellectual tango enriches scientific understanding, showcasing the beauty of complementary perspectives in the pursuit of knowledge.

 

[Winthrop]

The headline shows how far Scientific American has sunk since I was a child.

Or is this simply the decline of all print media and perhaps the fact that your perception of science may have changed with a few years of post secondary education?

At least they managed not to make the article political.

 

[PeterNSteinmetz]

I’m pretty sure they are generally worse. Many of their articles now are rather politically slanted. I don’t remember that being at all the case before.

 

[Winthrop]

Too bad, Holtzbrinck Publishing Group used to be ok, like Die Zeit had a mild left institutional bias, but still ok, e.g. like the Economist.

O tempora, o mores