Backwash Causes Lift?

On Tue, 02 Oct 2007 20:33:46 -0700, george wrote:

On Oct 3, 1:57 pm, Le Chaud Lapin wrote:

"In addition to the lowered pressure, a downward-backward flow of air
also is generated from the top surface of the wing. The reaction to
this downwash results in an upward force on the wing which demnstrates
Newtons' third law of motion. This action/reaction principle also is
apparent as the airstream strikes the lwoer surface of the wing when
inclinded at a small angle (the angle of attack) to its direction of
motion. The air is forced downward and therefore causes an upward
reaction resulting in positive lift."


I blame the lift pixies myself

I thought it was how the airflow goes through the splaps?

Bertie the Bunyip wrote:
Though if oyu send me some crack I do have some chickens I could try it on.

Bertie

Chicken you have, eh?

I want to be clear. I did not me to say "no one" is doing the
physics. Obviously there are chickens all over the
world. What I mean to say is that there seems to be a lot of farm fowl
who are using Bernoulli's principle somewhat carelessly, IMO. Some of
these roasters are CFI's (Chicken Food Items). Please don't ask me to name
individuals (Rhode Island Reds, Faverolles) but I know with certainty that
there are at least 2 living, breathing
guinea hens who do not understand where 29.92 Hg comes from, or does not
understand it well enough to make it make sense to other livestock. They
might have understood it at one point, but they don't now. I know
because I asked them and ate them.
My feelings about teaching is that if you are
not very certain about something, you do more damage than talking
about it. Of course, this leads to the conundrum of having to explain
to chickens why a sparrow stays in the air without providing erroneous
information. If I were a delicious farm fowl, I would simply say that the
marinade's
result in pressure below skin is sufficient to counteract pressure
above breast meat for force of gravity.
If they wanted to know more, I'd direct them to book on preparing delicious
poultry.

I don't think actually roasting a bird will explain the thermodynamic
contraction of proteins any more than braising a cow will help with
understanding of BBQ rack of ribs. Yes, there will be an an intuition
that will develop, but that's going to happen anyway, and that would
have happened even if I were a 16-year-old sitting in a restaurant.
Doesn't mean that 16-year-old is going to understand food science.

Let's face it. A large pecentage of people walking this planet think
there is a "poultry" force. I was watching the History Channel one
day, and the narrator actually used that term - a "poultry" force, and
he did not mean the force that is on the other side of the grill
where the "poultry" force was being applied. I've also seen countless
erroneous explantions on the same channel about bovine slaughter methods,
which I do
know about. Typically the narrator will say captured bolt when he meant
head-whacker, or ZAPPO! when he meant lethal humane execution.


I'm more of a mind-over-muncher type. I'll get my bib on and nibble
around and develop the intuition that you mention, certainly, but
that's not enough.


sorry, this all was seeming a bit tedious to me.

--
Message posted via http://www.aviationkb.com

On Oct 3, 3:49 pm, "Kloudy via AviationKB.com" u33403@uwe wrote:

sorry, this all was seeming a bit tedious to me.

ROFL!!!!

-Le Chaud Lapin-

On 3 Oct, 17:56, Mxsmanic wrote:
Le Chaud Lapin writes:
For example, as I mentioned earlier, I am reading Jeppesens Private
Pilot manual, and there are clearly errors in concept the manual
(energy being created by engine, for example), even though Jeppensen
probably has access to as many Ph.D. laureates as they want.

Describe the errors in a letter and send it to them. Good technical
publishers are always willing to accept corrections.

Thus the pile of "thank you for your input" letters.

Froootloop.

Bertie

On 3 Oct, 21:11, Le Chaud Lapin wrote:
On Oct 3, 1:33 pm, wrote:

On Oct 3, 10:56 am, Le Chaud Lapin wrote:

On Oct 3, 10:34 am, wrote:

Both Newton and Bernoulli are correct. Even inside a pipe the
static pressure drops as velocity increases. That's why your bottom
table jumps as you yank off the top one: you accelerated an airflow.
And in generating lift there's a displacement of air. Can't escape
that at all.

Also, if you don't mind, I would like to understand what you mean
here.

It's not clear to me.

[explanation of Bernoulli's principle clipped].

I did not mean that I did not understand Bernoulli's principle.

What I am saying is that I do not believe that the bottom table jumps
because of airflow acceleration. In fact, if I were to use tables
with circular faces, and put the entire apparatus in a giant
cylindrical tube, and pull up on the top table, assuming that the very
bottom of the tube were open-ended, the bottom table would follow the
top table upward, no matter how fast any air inside the tube were
moving. I could move the top table one molecular diameter every
10,000,000 years, and after the top table has moved, say, 0.5 meters,
the bottom table will follow. This assumes, of course, that the
appartus is airtight, that no air from outside the tube can squeeze in
between the walls of table and tube to fill the void that was created.

There are 14.7 lbs per square inch of pressure pressing upward against
the underside of the bottom table. The yanking of the top table
creates a vacuum between the two faces of the table. The lack of
pressure on the top of the bottom table leaves nothing to counteract
the pressure pressing upward on the underside of the bottom table.
Then the only thing holding the bottom table on the floor is gravity.
Assuming that the table is a typical table of typical weight and size,
one is guranteed that the impulse net pressure of 14.7lbs / in^2 is
enough to overcome gravity and lift the bottom table off the floor.

Note that this really has nothing to do with Bernoulli's principle or
dynamic pressures.

If it is still not clear, put the assembly in a tube again, anchor the
bottom table with a tie wire so it cannot move upward, and using a
hydraulic jack, pull the top table upward, then stop, wait a minute,
have a Coke (sipping with a straw of course), then take cutters and
snap the wire holding the bottom table to the floor.

At the precise moment that the wire is snapped, there is no movement
of anthing at all. There is no Bernoulli action.

The bottom table will rush up toward the top table, even slamming
against it quite hard if the coefficient of sliding friction between
table-side and tube wall is low enough.


Whoowh!
Zero point energy!

In my own kitchen!

I can tell the electric company to **** off now.


Bertie

On 3 Oct, 22:09, Le Chaud Lapin wrote:
On Oct 3, 3:49 pm, "Kloudy via AviationKB.com" u33403@uwe wrote:



sorry, this all was seeming a bit tedious to me.

ROFL!!!!

-Le Chaud Lapin-

Ah, a cluelessness vaguely remiscent of someone else I may have seen
around here.

Bertie

"Bertie the Bunyip" wrote

He's an idiot, what else does one need to know?

And yet so many can not resist posting replies to his posts, either with
corrections or witty zingers.

I'm starting to think that they are the bigger losers.

What we have lost is a good newsgroup. Why can't everyone see that when
they reply, he wins. And wins and wins.....

Folks, I'll say it _again_.

The ONLY way to get rid of a know-nothing, know-it-all, obnoxious troll, is
to IGNORE him. ALL of him. EVERY time, not just when you feel like it.

I thought we were turning a corner a couple days ago, with very few replies
to him being posted. Guess again.

Sigh.
--
Jim in NC

Bertie the Bunyip wrote in
ups.com:

Ah, a cluelessness vaguely remiscent of someone else I may have seen
around here.

Bertie

I wonder if Mx is really Bobo in sheep's clothing.

--

It is clearly time to revisit airplanes taking off on tredmills.

I have to agree. ANYTHING would be better than hearing the resident idiot
troll's blithering.

It goes something like this.

An airplane is about to takeoff on a runway, that is really a treadmill; a
very expensive treadmill.

The treadmill senses the airplane's speed, and matches the aircraft's speed,
with speed increases of its own.

Can the airplane takeoff? Why or why not?
--
Jim in NC

Le Chaud Lapin writes:

Also, if you don't mind, I would like to understand what you mean
here.

You can only push the wing upward if something else is pushed downward. Thus,
the wing generates lift only to the extent that it diverts a substantial mass
(of air) downward. No downwash, no lift.