Re: Not sure
- Hi Pete,
Similar maybe, but with opposite effects. Vortices from rigid wings
generate drag. Vortices from flapping wings generate lift.
Go to http://tinyurl.com/379eb2 for "Against All Odds: How Bugs Take
Wing" and to http://tinyurl.com/ys85lf for "Optimal' vortex rings and
aquatic propulsion mechanisms."
Best wishes, Frank
--- In firstname.lastname@example.org, "Pete B." <georgeyyy@...>
> The vortex rings that you mention are similar to the vortex at the end
> of the wings on aircraft. The addition of winglets minimize the effect
> of the vortex rings.
> [Blended Winglets]
> --- In email@example.com, "Frank McNeill"
> <frankmcneilll@> wrote:
> > Hi, Jean-Yves, Pete, Carl and all,
> > I have also seen something about that elusive boat with a pop-pop
> > boiler made of barrel heads and have searched for it several times
> > with no results.
> > The last search turned up something at http://tinyurl.com/2342fk about
> > a method for generating vortex rings that might have changed history
> > if James Rumsey had known about it. For a connection between vortex
> > rings and propulsion Google for squids.
> > Best wishes to all, old Frank
- ----- Original Message -----
From: "Pete B."
The vortex rings that you mention are similar to the vortex at the end
of the wings on aircraft. The addition of winglets minimize the effect
of the vortex rings.
The crucial difference is that vortices impede a soaring creature but
enable a swimming one.
It's obvious that squid swim and eagles (with their winglet feathers) soar.
What isn't obvious is that insects swim though the air ( hence the old joke
about "according to the laws of aerodynamics a bumblebee is unable to fly,
but fortunately nobody has told the bee").
And that little birds chop and change. I caught a sparrow in my house last
week and took it out of doors in a bucket. It flew straight up vertically
like a helicopter (swimming) before gliding across the street (soaring).
I suppose this is wandering off topic so I'll stop before we get on to
propellers . . . ;-)
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Hi David & Frank,
It's fascinating how Science can contradict itself. In the case of vortices the configuration and dynamics determine whether they are a help or a hinderance.
I was unaware of that phenomenon. Who said that you can't teach an old dog new tricks? How do bumblebees fly? What about hummingbirds? I watched 3 fly around flowers yesterday. It's amazing that they are able to maintain the wind speed that they do.
Thanks for the contributions.