Bernoulli principle bunk?

[MissedApproach]

Interesting stuff,
Basically this guys saying that a wing generates lift not through bernouillis principle but more so through newtons basic laws of physics.

NPR interview with David Anderson

Explanation

[USMCmech]

Ahh it's time to revisit the popular Bernouli vs Newton debate.

These are fun because they are almost as civil and fact based as Airbus vs Boeing, or Lycoming vs Contential.


In the right corner is Bernouli who discovered that the faster a fluid moves the lower pressure it has. (I'm told he was trying to fix his towns sewer system) Airplane wings use this by forcing air flowing ove the top of the wing to go faster creating lower pressure and sucking the wing up.

In the left corner is Issac Newton he discovered that for every action there is a reaction (also a little thing called graviety). If you hold a piece of plywood (or a wing) at an angle to the wind, the airsteam hits the bottom of it and forces it up. Many people in Florida discovered this recently.

Gentelmen come out fighting and I don't want to see any low blows.


The facts are that lift comes from a combination of the two factors. About 70/30 Bernouli/Newton. At slower speeds Newton provides a greater portion, while at higher speeds Bernouli does most of the work.

Airfoil design also plays a important factor. Symetrical airfoils on many areobatic planes do use Bernouli with their AoA, but they use a lot of Newton.

If you don't belive me, go to your local college and ask somebody from the enginering department.




I will now attempt to stear the conversation to a more intelectual debate.

Airbus sucks Boeing rules!!

[roundout]

[ QUOTE ]
I will now attempt to stear the conversation to a more intelectual debate.

Airbus sucks Boeing rules!!

[/ QUOTE ]


a winner is you


yatta!

[pscraig]

Ever hear about Coanda?

[PhotoPilot]

A yes, Coanda. The little known force that provides hours of fun with a highlighter and a steady stream of tap water. Coincidentally, it also helps keep us in the air . . .

[seagull]

Ugh! Why don't you look at the "ground effect" thread below, it is well described! It is not "70/30" or what ever. It is one and the same, except for ONE special case, and that is "impact lift" which only applies to very high speed/high altitude flight! Aside from that, Bernoulli = Newton, they are different ways of describing the SAME THING! The equations of Bernoulli come from Newton!

[Minuteman]

Seagull you're my new hero!

[USMCmech]

Obviously there is a lot more going on with the airflow around airplanes than can be explained in laymans terms.

The simplistic ways that lift is described to new pilots (and even CFIs) is just a general description. Areonautical enginers understand the complexities of lift and everything involved.

I know that lift comes from a combination of foward speed and angle of attack. The Bernouli/Newton 70/30 explaination is a good simple way to describe it.

Anything more than that I will leave to the guys with the big calculators.

[PhilosopherPilot]

[ QUOTE ]
Ugh! Why don't you look at the "ground effect" thread below, it is well described! It is not "70/30" or what ever. It is one and the same, except for ONE special case, and that is "impact lift" which only applies to very high speed/high altitude flight! Aside from that, Bernoulli = Newton, they are different ways of describing the SAME THING! The equations of Bernoulli come from Newton!

[/ QUOTE ]

Here we go again Seagull....

G

[seagull]

No, the 70/30 thing is akin to saying that you'll stall if you turn downwind. Complete rubish.

I highly recommend you go pick up a copy of Flightwise by Chris Carpenter, available on the amazon UK or Canadian site (not the U.S. one, so click the link at the bottom) and READ IT! Better yet, buy the second volume as well and read them both!

[FLY_CRJ]

This was posted a few months ago, it does a great job of explaining the details.

http://travel.howstuffworks.com/airplane5.htm

[pavelump]

[ QUOTE ]

In the left corner is Issac Newton he discovered that for every action there is a reaction (also a little thing called graviety). If you hold a piece of plywood (or a wing) at an angle to the wind, the airsteam hits the bottom of it and forces it up. Many people in Florida discovered this recently.


[/ QUOTE ]

Uh, no.

Check out this website from the fine folks at NASA. They know a thing or two about aerodynamics.

Incorrect theories about lift.


Dave

[USMCmech]

From the website (which was really cool BTW)

[ 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.


[/ QUOTE ]

My scartastic comments about the two sides were meant to show how oversimplified they are.

As I said origionally, lift comes from a complex combination of factors. The two most important to pilots are airspeed and AOA.

The higher math calculations I leave to Areonautical enginers. Realisticly we as pilots don't need to understand much more than this because most everythin else is out of our control.

[pavelump]

[ QUOTE ]
My scartastic comments about the two sides were meant to show how oversimplified they are.

[/ QUOTE ]

Agreed. I'm in an advanced aerodynamics class this semester and my eyes have been opened to a lot of misinformation that I have received over the years. A lot of it from reputable "in print" sources.

I think that we all really know the reason that an airplane flys though.

Money.


Dave

[seagull]

I think that one must remember the equations are really just models so we can calculate how much force there is. It doesn't take any math to understand what's happening or why, in my opinion, only to get numbers out of it.

Not unlike the engineering "reason" that swept wings reduce mach effect, where they divide the airflow into two streams, one perpendicular to the leading edge and the other along it. Does this tell you anything about WHY swept wings work? Nope, not at all, all they do is allow for calculations of how much various amounts of sweep will affect the problem. The "why" is simple enough that it can be explained in laymans terms to any private pilot!

[PhilosopherPilot]

By the way, I bought the book that the NPR discussion was about. Good book, and very easy to understand. Understanding Flight by David F. Anderson and Scott Eberhardt.

It provides clear explanations, without a lot of mathematics.

G

[seagull]

If you liked that book, you'll love "Flightwise" by Chris Carpenter.

[chris]

Seagull,

I ordered Flightwise recently, as per your recommendation

I hope it is a good book, and will supplement other books that I recently read (Stick and Rudder, Advanced Pilot's Manual, See How It Flies, and Flight Theory for Pilots).

I want a book that gives a correct and scientific explanation of aerodynamics and principles affecting flight. "Aerodynamics for Naval Aviators" was also recommended to me- I hope the Flightwise book is as advanced and good as this one.

I'll let everyone know what I think of the book when I'm done!

Chris.

[seagull]

Did you order both books, there is a volume 1 and 2? Flightwise is far and away the best of any of them I have ever seen, and I've read all the others mentioned here.

[chris]

Seagull,

No, I only ordered Volume 1. If I like it, I will probably order Volume 2.

I ordered it off the Canadian amazon.ca site. It was selling for 30% off, and I ordered it for under $40 Canadian (about $32 USA). Both volumes were selling for the same price.

[USMCmech]

Bump


We hashed this out a few months back.

Read the whole thread carefully, and check out the links.