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Lift - Newton/Bernoulli ratio...



 
 
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  #31  
Old May 24th 11, 02:26 PM posted to rec.aviation.piloting
Dave Doe
external usenet poster
 
Posts: 378
Default Lift - Newton/Bernoulli ratio...

In article 6def6450-011d-4f9f-8595-8c455f6b6ea0
@hd10g2000vbb.googlegroups.com, , a says...

On May 22, 10:02*pm, brian whatcott wrote:
On 5/22/2011 5:15 AM, Dave Doe wrote:

Does anyone have any figures and references for about what ratio lift is
produced by Newton's Laws and Bernoulli's Laws?


I appreciate this is not a static figure - but say a yer average C-172,
or perhaps a 737.


I would hazard a semi-educated guess that lift is *primarily* produced
by angle of attack (or deflection if you like) - Newton's Laws - and by
a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's
principle might create 20% of the lift a wing generates. *A friend
believes it would be much lesser - about 5%.


Think of it this way:
Newton: force is proportional to the mass and its acceleration.

In this context, the meaning is, to produce the aircraft's weight in
lift i.e. upwards , an airmass has to move *with sufficent acceleration
to provide that up force.

Bernoulii: the mass of air flowing through a channel times its speed
gives the same product even if the channel then narrows to a waist:
the air mass has to flow faster, but its pressure drops..

In this context: air flowing in an airstream over a wing sees it bulging
(or waisting) and so that it needs to speed up, and pressure drops over
the upper wing. Arguments of this type can be used as evidence that 2/3
of the wing lift is produced at the upper surface, and 1/3 at the lower
wing surface.

The larger truth: air pressure drops over the upper surface of a wing,
and increases over the lower surface of a wing, and the resultant
downflow balances the lift on the wing.

Brian W


Does it matter to anyone posting here that the fluid flow described
by Berboulli's equation assumes the fluid is incompressible? Does
anyone here really believe there is no change in air density as if
flows at speeds of a hundred miles an hour past an airfoil? The
equation works well for water flow in pipes and around boat hulls. It
does not do such a good job of predicting pressures along an airfoil.
Stick with Newtonian Physics and the gas laws.


I think you are right - and I think most here would agree. Hoewver it
is, for practicle purposes, considered (or treated as) incompressible at
speeds under Mach 0.3 (something I read somewhere in my research).

In reality, air is of course *very* compressible, compared to say water.

--
Duncan.
  #34  
Old May 24th 11, 02:29 PM posted to rec.aviation.piloting
David Dalton
external usenet poster
 
Posts: 1
Default Lift - Newton/Bernoulli ratio...

On Wed, 25 May 2011 01:21:09 +1200, Dave Doe wrote:

We're talking lift here mate - that's in the upwards direction!


Do you know of any past or present figure other than me
who uses the base chakra area muscle click (involuntary)
as closure to a magickal working? Or for divination?
I believe that Myrddin, one of the historical figures that
the legend of Merlin may have been based on, did this false
divination when he consulted his "little piggy" in the
forest. That is, I think that his "little piggy" was his
base chakra.

Oh, I forgot to define the base chakra area muscle click or short
period mulabhanda to those who don't know what a base chakra
is.

Basically the base chakra area is the perineum, or area between
the genitals and the anus. I think in a chicken this is known
as the pope's nose (correct me if that is some other area).

The click or jerk or short period mulabhanda is a clenching
of the muscles in this base chakra area. For a longer
period mulabhanda the muscles are held clenched but for
this click they are clenched and quickly released.

David
  #35  
Old May 24th 11, 03:35 PM posted to rec.aviation.piloting
Dudley Henriques[_3_]
external usenet poster
 
Posts: 66
Default Lift - Newton/Bernoulli ratio...

On May 23, 9:31*pm, a wrote:
On May 22, 10:02*pm, brian whatcott wrote:









On 5/22/2011 5:15 AM, Dave Doe wrote:


Does anyone have any figures and references for about what ratio lift is
produced by Newton's Laws and Bernoulli's Laws?


I appreciate this is not a static figure - but say a yer average C-172,
or perhaps a 737.


I would hazard a semi-educated guess that lift is *primarily* produced
by angle of attack (or deflection if you like) - Newton's Laws - and by
a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's
principle might create 20% of the lift a wing generates. *A friend
believes it would be much lesser - about 5%.


Think of it this way:
Newton: force is proportional to the mass and its acceleration.


In this context, the meaning is, to produce the aircraft's weight in
lift i.e. upwards , an airmass has to move *with sufficent acceleration
to provide that up force.


Bernoulii: the mass of air flowing through a channel times its speed
gives the same product even if the channel then narrows to a waist:
the air mass has to flow faster, but its pressure drops..


In this context: air flowing in an airstream over a wing sees it bulging
(or waisting) and so that it needs to speed up, and pressure drops over
the upper wing. Arguments of this type can be used as evidence that 2/3
of the wing lift is produced at the upper surface, and 1/3 at the lower
wing surface.


The larger truth: air pressure drops over the upper surface of a wing,
and increases over the lower surface of a wing, and the resultant
downflow balances the lift on the wing.


Brian W

theories
anyone here really believe there is no change in air density as if
flows at speeds of a hundred miles an hour past an airfoil? The
equation works well for water flow in pipes and around boat hulls. It
does not do such a good job of predicting pressures along an airfoil.
Stick with Newtonian Physics and the gas laws.


The ideal gas law still applies. Compressing airflow does indeed
complicate Bernoulli as do the density changes involved but Bernoulli
still holds up. Both theories remain correct even with compressible
flow. But you are correct in that the Newton explanation is FAR easier
of the two for people to deal with and understand. The only caveat I
stress to instructors when getting into the lift issue is that they
NEVER explain lift using ONLY one theory without mention of the other,
as student pilots, once exposed to the lift question will invariably
find through a credible source that BOTH Newton and Bernoulli are
correct and that each can explain exactly the same thing to the 100%
point.
Lift can be explained to death. The deeper one goes into the
explanation the more complicated it can get. Denigrating Bernoulli due
to changing density and airflow speeds causing compression factors is
NOT the way to present lift. Bernoulli stands. It's the math that gets
harder when you compress the flow that's all. All this can be avoided
by simply explaining to students that lift results when an airflow is
TURNED, and BOTH Newton and Bernoulli can be shown to cause the
airflow to turn as lift is being produced. Circulation, density,
vortices..........all part of it, but it's the turning of that airflow
that produces lift force and BOTH Bernoulli and Newton are working
equally to produce that force, only doing it differently.
Dudley Henriques
  #36  
Old May 24th 11, 03:56 PM posted to rec.aviation.piloting
Orval Fairbairn
external usenet poster
 
Posts: 824
Default Lift - Newton/Bernoulli ratio...

In article
,
Dudley Henriques wrote:

On May 23, 9:31*pm, a wrote:
On May 22, 10:02*pm, brian whatcott wrote:









On 5/22/2011 5:15 AM, Dave Doe wrote:


Does anyone have any figures and references for about what ratio lift is
produced by Newton's Laws and Bernoulli's Laws?


I appreciate this is not a static figure - but say a yer average C-172,
or perhaps a 737.


I would hazard a semi-educated guess that lift is *primarily* produced
by angle of attack (or deflection if you like) - Newton's Laws - and by
a much lesser degree by Bernoulli's Law. *I would guess that Bernoulli's
principle might create 20% of the lift a wing generates. *A friend
believes it would be much lesser - about 5%.


Think of it this way:
Newton: force is proportional to the mass and its acceleration.


In this context, the meaning is, to produce the aircraft's weight in
lift i.e. upwards , an airmass has to move *with sufficent acceleration
to provide that up force.


Bernoulii: the mass of air flowing through a channel times its speed
gives the same product even if the channel then narrows to a waist:
the air mass has to flow faster, but its pressure drops..


In this context: air flowing in an airstream over a wing sees it bulging
(or waisting) and so that it needs to speed up, and pressure drops over
the upper wing. Arguments of this type can be used as evidence that 2/3
of the wing lift is produced at the upper surface, and 1/3 at the lower
wing surface.


The larger truth: air pressure drops over the upper surface of a wing,
and increases over the lower surface of a wing, and the resultant
downflow balances the lift on the wing.


Brian W

theories
anyone here really believe there is no change in air density as if
flows at speeds of a hundred miles an hour past an airfoil? The
equation works well for water flow in pipes and around boat hulls. It
does not do such a good job of predicting pressures along an airfoil.
Stick with Newtonian Physics and the gas laws.


The ideal gas law still applies. Compressing airflow does indeed
complicate Bernoulli as do the density changes involved but Bernoulli
still holds up. Both theories remain correct even with compressible
flow. But you are correct in that the Newton explanation is FAR easier
of the two for people to deal with and understand. The only caveat I
stress to instructors when getting into the lift issue is that they
NEVER explain lift using ONLY one theory without mention of the other,
as student pilots, once exposed to the lift question will invariably
find through a credible source that BOTH Newton and Bernoulli are
correct and that each can explain exactly the same thing to the 100%
point.
Lift can be explained to death. The deeper one goes into the
explanation the more complicated it can get. Denigrating Bernoulli due
to changing density and airflow speeds causing compression factors is
NOT the way to present lift. Bernoulli stands. It's the math that gets
harder when you compress the flow that's all. All this can be avoided
by simply explaining to students that lift results when an airflow is
TURNED, and BOTH Newton and Bernoulli can be shown to cause the
airflow to turn as lift is being produced. Circulation, density,
vortices..........all part of it, but it's the turning of that airflow
that produces lift force and BOTH Bernoulli and Newton are working
equally to produce that force, only doing it differently.
Dudley Henriques


AMEN!
  #37  
Old May 24th 11, 08:03 PM posted to rec.aviation.piloting
Dudley Henriques[_3_]
external usenet poster
 
Posts: 66
Default Lift - Newton/Bernoulli ratio...

On May 24, 3:26*pm, "Private" wrote:
"Dudley Henriques" wrote in message

...
snip
Absolutely..........without question! *The EXACT same explanation of
lift creation is in play on an inverted wing as on the upright wing.
Applies to barn doors as well.
Newton= 100% *Bernoulli= 100%.
Dudley Henriques

Greetings Dudley,
Glad to see that you have not abandoned hope for this place.
Hope you are well.
Best Wishes and Happy Landings.


Thank you for the kind thought. Just passing through.
DH
  #38  
Old May 24th 11, 08:26 PM posted to rec.aviation.piloting
Private
external usenet poster
 
Posts: 188
Default Lift - Newton/Bernoulli ratio...


"Dudley Henriques" wrote in message
...
snip
Absolutely..........without question! The EXACT same explanation of
lift creation is in play on an inverted wing as on the upright wing.
Applies to barn doors as well.
Newton= 100% Bernoulli= 100%.
Dudley Henriques

Greetings Dudley,
Glad to see that you have not abandoned hope for this place.
Hope you are well.
Best Wishes and Happy Landings.


 




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