The Mystery of Fly Flight: Debunking Bernoulli's Law Explanation

[Cyrus]

And yet they still produce adequate lift at low sub-sonic speeds, and with the "hump" on the bottom of the wing instead of the top. Compare the angle off attack of the F104 (essentially a jet powered missle with tiny wings) to the M2-F2. The M2-F2 picture is a bit deceiving since the photo is angled a bit.

The M2-F2 and M2-F3 are good examples to "disprove" equal transit theory as the cause of lift, and I just find them interesting, as they are fairly unique.

I rotated the picture 2 degrees right to make the ground appear level, still the upper surface of the m2-f2 is nearly horizontal, but it could be in a "flare" since it's landing, but the wheels are still up, so even though it's fairly low, it's got some gliding time left to deploy the landing gear.

Also the top surface isn't completely flat, it tapers at the tail, but the main point is shape of the lower surface, and the fact that the bottom surface is the "longer path".

You have to be careful, just by looking at a picture gives you no indication of the AoA of those two aircraft. All you're seeing in this photo is the flight path angle - not the AoA.

Despite this, it is a very interesting aircraft design! It looks like a delta wing with the pilot all the way forward for stability in pitch.

 

[FredGarvin]

That is exactly correct. The NS equations are true - period. It is the NS equations that CFD solves.

Approximates. N-S equations have very few situations that can be solved exactly.

That is called, 'momentum theory'.

AKA "Actuator Disc Theory."

 

[Cyrus]

Approximates. N-S equations have very few situations that can be solved exactly.

AKA "Actuator Disc Theory."

N-S doesn't have a closed form solution, implied in my post was the necessity to use something like CFD to solve them. That does not make the N-S equation an approximation. The solution is an approximation to the N-S equations, but the Equations are not an approximation.

*The only real "approximation" is that the gas particles follow a continuum.

As for Actuator Disc Theory, tom-a-to, to-ma-to.

 

[Cyrus]

I left half way into the talks because I have work to do. But what I did see was pretty interesting. A guy from CalTech had optical sectioning images of a fly. Basically, they use special infrared laser beams to scan the fly and you can see all the internal structure of the fly just like a 3d MRI. The fly has two muscles that cause the complex flapping motion. One main muscle always powers the flies wings, while these two muscles adjust the tension, and thus the equivalent spring constant to change the flapping properties. Pretty non-intuitive. There were also a video of a honey bee inside a wind tunnel given a wind gust disturbance, and a high speed strobe video of a fly with a piece of string tethered onto its back to keep it stationary.

 

[lividz]

Look this was shown on discovery...
actually the wings of the fly create whirl of wind[sorry for that..I can't find the exact word now...hope u understand what I want to convey]...on its lower back side...this is the main cause of lift

 

[Cyrus]

Look this was shown on discovery...
actually the wings of the fly create whirl of wind[sorry for that..I can't find the exact word now...hope u understand what I want to convey]...on its lower back side...this is the main cause of lift

You do realize, I was sitting in a room with Dr. Michael H. Dickinson and other experts from the around the country that deal with this...right?

http://dickinson.caltech.edu/old/index.html

 

[Phrak]

Birds and insects fly in several modes. The flapping wing and flap-slap are the most well know.

It takes a few cord lengths to generate the captive vortex encircling the wind before it can develop good lift (Wagner effect). The figure eight motion (and who knows what else?) enables hovering flight.

 

[lividz]

^so...I didnt read it at that time..but thanks for info...

 

[Phrak]

^so...I didnt read it at that time..but thanks for info...

Oh, OK, Lividz. Now I understand your post.

 

[lividz]

^no that was targeted @cyrus:

You do realize, I was sitting in a room with Dr. Michael H. Dickinson and other experts from the around the country that deal with this...right?

No, I just realized that!
I posted it just by reading the very 1st post...and as u may b knowing they don't show the hardcore details on shows abt such things...

neways...ok...coz its my mistake...that I posted a useless post .. just by knowing a small fraction of the whole scene...

but cyrus post conveys that there r sum guys who can explain it to me in much more details than I could ever get from other sources...thats good...

Lemme go thru the posts till now...

 

[Cyrus]

<Moan> Please take the time to type in full English or don't bother posting.

 

[drizzle]

^no that was targeted @cyrus:



...

try to use the quote feature next time

 

[FredGarvin]

The solution is an approximation to the N-S equations, but the Equations are not an approximation.

That was my point. One rarely solves the N-S equations. They approximate them.

 

[Phrak]

Check out this particular study on dragonfly wings and cross sectional corregations that result from veins in the wings.

http://jeb.biologists.org/cgi/reprint/203/20/3125.pdf"

 

[Cyrus]

Check out this particular study on dragonfly wings and cross sectional corregations that result from veins in the wings.

http://jeb.biologists.org/cgi/reprint/203/20/3125.pdf"

Thanks for this article, I'm going to forward it to my advisor! Very interesting results too!