Re: Thrusting or Sucking (where's Howard Stern when we need him.)

In article <Npidnfx2L64jKl_enZ2dnUVZ_sydnZ2d@xxxxxxxx>,
Bruce <bgpub@xxxxxxxxxxxxx> wrote:

> Here is a stab at a simple explanation -
>
> The crux of the matter is that aircraft fly by the transfer of energy. Fluid

Point of order: transfer of *momentum*. In order to fly, a
heavier-than-air aircraft must apply a certain force to the air,
transferring momentum to it. The amount of momentum transferred is
constant across the aircraft's performance envelope, whereas the energy
transfer varies.

> dynamics and physics provide us with a variety of tools to model how this
> happens.
>
> A famous quote from IT applies - "All models are false, some models are
> useful"
>
> Depending on the situation one or another model may be more useful and/or
> accurate, but they remain models. We are generally concerned with low
> Reynolds
> numbers and laminar flow over low lift+low drag wings. In this regime the
> contribution of upper surface lift is apparently no less than 1/3 of the
> total,
> and at low angle of attack it may be greater than 50%.
>
> The net result of Bernoulli, Prantl et al is that a moving wing transmits
> kinetic energy to the air. As long as the air flows around the wing in a
> relatively orderly fashion, the reaction is lift (varying amounts of suck and
> blow), if the flow becomes chaotic (stalled) we get primarily drag.(Very
> simple.)
>
> Conversely - calculating how much will be created, and optimising efficiency
> over a range of performance requires serious computational power and a head
> for
> calculus. (very complex)
>
> Nyal Williams wrote:
> > Newton explains it better than Bernoulli. The FAA
> > written for PSEL no longer requires the Bernoulli answer
> > about lift.
> >
> > Go to Amazon.com or Bookfinder.com and look for a book
> > by Gale Craig, titled, 'Stop Abusing Bernoulli! - How
> > Airplanes Really Fly '. (Search under Craig, Gale.)
> > Gale is a physicist who enquired into this subject.
> > Used copies are listed there, but the book is self-published
> > and you can order fresh copies from him. He lives
> > in Anderson, Indiana. Anyone who is interested in
> > that address should write me and I will get it for
> > you.
> >
> > At 17:00 09 January 2006, Marty wrote:
> >
> >>Stick the cambered side of a standard spoon under a
> >>running tap! Ease
> >>the cambered side of the spoon gradually into the running
> <SNIP>

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."
.

Relevant Pages

  • Re: Mxsmanic , IFR sensations, and some other stuff
    ... anytime you have lift being created you have a Newton ... explanation AND a Bernoulli explanation occurring at the SAME TIME! ... at the same time that the air flowing under the wing does, ...
    (rec.aviation.piloting)
  • Re: Mxsmanic , IFR sensations, and some other stuff
    ... of the aerofoil of the wing ... ... The air is diverted because the wing has a positve angle of attack. ... I thought that one of the most interesting points he made was that the lift ... I just can't understand why there is so much trouble in the pilot community understanding that Newton and Bernoulli do NOT conflict in any way whatsoever, and that each explanation is correct in itself. ...
    (rec.aviation.piloting)
  • Re: Mxsmanic , IFR sensations, and some other stuff
    ... anytime you have lift being created you have a Newton ... According to the article where Bernoulli falls apart is in the assumption ... at the same time that the air flowing under the wing does, ... indeed incorrect, but it's CRITICAL that a pilot reading this completely ...
    (rec.aviation.piloting)
  • Re: Mxsmanic , IFR sensations, and some other stuff
    ... anytime you have lift being created you have a Newton ... at the same time that the air flowing under the wing does, ... What Garrison is talking about is the equal transit theory, which is indeed incorrect, but it's CRITICAL that a pilot reading this completely understand that it isn't Bernoulli that is incorrect, but rather the equal transit theory that is incorrect. ...
    (rec.aviation.piloting)
  • Re: Mxsmanic , IFR sensations, and some other stuff
    ... anytime you have lift being created you have a Newton ... explanation AND a Bernoulli explanation occurring at the SAME TIME! ... at the same time that the air flowing under the wing does, ... indeed incorrect, but it's CRITICAL that a pilot reading this completely ...
    (rec.aviation.piloting)
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