Flight Theory - It's An Unsolved Science Dilemma

[calyptorhynchus <>]

It would be interesting to see if Hummingbirds share these innovations, as they they are closely related to Swifts.

John Leonard

On Mon, 12 Oct 2020 at 09:58, Michael Tarburton <> wrote:

Well said Jason.

Lund University has been running Wind tunnel experiments on many species of birds.  They discovered 20 years ago that Swifts have a totally different mechanism for flying - some of the maths for this is beyond me and even they admit they do not understand the full mechanism.  They told me they had aeronautics people there for about a year looking at what they were doing.  A year and a bit later Boeing came out with  the new Dreamliner, which has very swift-like design, 2 less engines, carries more passengers (more safely) than its predecessor and uses significantly less fuel.

Two of their papers are:  

Henningsson, P., G.R. Spedding, & A. Hedenström. 2008.

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel.  

the Journal of experimental Biology 211, 717-730.

Henningsson, P., Muijres, F.T., & A. Hedenström. 2011.

Time-resolved vortex wake of a common swift flying over a range of flight speeds.  

Journal of the Royal Society: Interface 8, 807-816.

These differences in a swifts wing are huge and present real problems for evolutionary theoreticians.

 

Cheers

Mike Tarburton.

On 12 Oct 2020, at 2:08 am, Jason Polak <> wrote:

I am a mathematician.

I have read the comments in this thread, and I am rather disappointed by
the spin Scientific American put on that article.

It's hardly the case that flight is a great mystery. What is difficult
is finding a complete explanation for flight in various detail from a
'high-level' basic physics perspective. While that is a lofty goal and a
worthy intellectual endeavour, that hardly means we "don't understand"
flight.

We may not understand flight from a "top-down" perspective, but we
already have extremely good models in terms of Navier-Stokes equations
and variants, derived from first basic physics principles, that describe
air flow. Therefore, starting from the basic premise of designing wings
on an airplane, we can write down equations that describe exactly what
will happen regarding its flight capability.

However, what we write down are equations, not high-level explanations.
It's no different than many other design problems in engineering. The
only difficulty is that the equations typically cannot be solved
analytically and they need simulation to solve them. However, that is no
great difficulty, as we can solve them approximately to any desired
accuracy and simulate them as well as needed.

There is no danger of airplanes coming down because we don't have a
simple high-level explanation of flight. Absolutely none.

When designing a new airplane, we don't need to be frightened because
simulation together with iterative design allows us to accurately
converge onto a solution mathematically, without the need for a
high-level understanding. The low-level understanding of air flow
(derived from physical principles) is sufficient to tell us what will
happen, even if we can't explain it from a conceptual point of view.

AND, even if we had a better explanation of all aspects of flight, the
complexity of air flow makes it virtually impossible that we will ever
be able to explain the nuances of every aspect of flight, such as the
difference in wing shape between say the Musk Duck and the Australian
Shelduck.

Countless aspects of our engineering and scientific knowledge proceeds
this way as well such as the design of car engines and musical
instruments. Many of the optimizations that go into a car engine are
based on low-level, simulatory knowledge of air flow, even if we cannot
articulate high-level reasons why the optimizations work.

Jason

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--

John Leonard
Canberra
Australia
www.jleonard.net

‘There is kinship between people and all animals. Such is the Law.’ Kimberley lawmen (from Yorro Yorro)

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