Opinions on NASA lift theory?

[Matt Herron Jr.]

Interesting read...

https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html

[Scott Williams]

On Sunday, July 1, 2018 at 9:08:44 AM UTC-5, Matt Herron Jr. wrote:
> Interesting read...
>
> https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html

Try "Stick and Rudder", by Langeweische.

But, of course flight is really just witchcraft ;-)

Scott

[George Haeh]

The previous webpage offers the correct mechanism:

https://www.grc.nasa.gov/www/K-12/airplane/right2.html

Note that in: F = m * dV/dt

F and V are vectors with components in 3 dimensions. Of course the z-axis is of most interest. Drag and vortex effects manifest themselves principally in the x and y axes.

And yes, there's a vast amount of mythology on lift generation in most pilot textbooks.

[jfitch]

On Sunday, July 1, 2018 at 11:17:23 AM UTC-4, George Haeh wrote:
> The previous webpage offers the correct mechanism:
>
> https://www.grc.nasa.gov/www/K-12/airplane/right2.html
>
> Note that in: F = m * dV/dt
>
> F and V are vectors with components in 3 dimensions. Of course the z-axis is of most interest. Drag and vortex effects manifest themselves principally in the x and y axes.
>
> And yes, there's a vast amount of mythology on lift generation in most pilot textbooks.

All of the several valid theories of lift are simply mathematical models, not the reality itself. The Bernoulli mechanism does in fact generate lift, but does not explain or predict it well, so it is best discarded as less than the whole picture. There's lifting line theory, circulation theory, deflection theory - no shortage of models.

[Charlie Quebec]

A wing deflects air downwards, and the upward force is applied to the wing via Bernoulli pressure distributions.
If you disagree, tell me where the reaction force is applied and how.
Every airfoil has a known pressure distribution, as this is the way airfoils are designed.
Simple, well known science.
Why the constant attempts at mumbo jumbo theories exist is a total mystery to me.

[Charlie Quebec]

https://www.mh-aerotools.de/airfoils/velocitydistributions.htm

[Marcel]

Nah, it's due to lift demons:
http://messybeast.com/dragonqueen/liftdemon.htm
(Author thanks Mary Shafer, NASA-Dryden (now NASA-Armstrong) for revealing the truth)

[Scott Williams]

On Sunday, July 1, 2018 at 9:08:44 AM UTC-5, Matt Herron Jr. wrote:
> Interesting read...
>
> https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html

I've also heard that it is the impact of ascending angels on the lower surface of the airframe, but they take breaks sometimes to pray, usually along with the pilot :-)

[Martin Gregorie[_6_]]

On Mon, 02 Jul 2018 06:42:46 -0700, Scott Williams wrote:

> On Sunday, July 1, 2018 at 9:08:44 AM UTC-5, Matt Herron Jr. wrote:
>> Interesting read...
>>
>> https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html
>
> I've also heard that it is the impact of ascending angels on the lower
> surface of the airframe, but they take breaks sometimes to pray, usually
> along with the pilot :-)

A similar theory about how competition free flight model aircraft was
around several years ago, only instead of demons, its creatures were
small, fat, furry Bernoulli Balls. Like the demons, these hold onto
models wings to support them when they are flying and won't go near a
really ugly model.

However, they are also responsible for thermals, which occur when crowds
of Bernoulli Balls dance around because they are warm, happy and excited.
Models that enter a thermal are grabbed and included in the dance. This
also explains why there are no thermals at night - the BBs are all
sitting on the ground, worn out by their day's activities.


--
Martin | martin at
Gregorie | gregorie dot org

[Dan Marotta]

So how does all of this (lift demons, CDU, etc.) explain the fact that
British aeroplanes [sic] also fly?Â* They make some of the ugliest planes
in the world, except for the Spitfire, there must have been a Frenchman,
an Italian, or an American involved in that design.

God bless the Queen!

On 7/2/2018 8:39 AM, Martin Gregorie wrote:
> On Mon, 02 Jul 2018 06:42:46 -0700, Scott Williams wrote:
>
>> On Sunday, July 1, 2018 at 9:08:44 AM UTC-5, Matt Herron Jr. wrote:
>>> Interesting read...
>>>
>>> https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html
>> I've also heard that it is the impact of ascending angels on the lower
>> surface of the airframe, but they take breaks sometimes to pray, usually
>> along with the pilot :-)
> A similar theory about how competition free flight model aircraft was
> around several years ago, only instead of demons, its creatures were
> small, fat, furry Bernoulli Balls. Like the demons, these hold onto
> models wings to support them when they are flying and won't go near a
> really ugly model.
>
> However, they are also responsible for thermals, which occur when crowds
> of Bernoulli Balls dance around because they are warm, happy and excited.
> Models that enter a thermal are grabbed and included in the dance. This
> also explains why there are no thermals at night - the BBs are all
> sitting on the ground, worn out by their day's activities.
>
>

--
Dan, 5J

[Martin Gregorie[_6_]]

On Mon, 02 Jul 2018 15:38:52 -0600, Dan Marotta wrote:

> So how does all of this (lift demons, CDU, etc.) explain the fact that
> British aeroplanes [sic] also fly?Â* They make some of the ugliest planes
> in the world, except for the Spitfire, there must have been a Frenchman,
> an Italian, or an American involved in that design.
>
Yep, most Blackburns and some planes from Fairey were ugly, but there are
even uglier so, after due consideration, I'd have to give the ugly prize
jointly to various prewar French and Russian aircraft, particularly their
big multi-engine stuff.


--
Martin | martin at
Gregorie | gregorie dot org

[Larry Suter]

This article contains the best physical argument for lift I've seen. The author simply explains why any shape that introduces curvature into the flowfield necessarily generates lift.

http://www3.eng.cam.ac.uk/outreach/Project-resources/Wind-turbine/howwingswork.pdf

WRT wings, you do need to accept attached airflow as an article of faith.

Larry

[[email protected]]

That article appears to be a reasonable effort.

Doug McLean in his book, "Understanding Aerodynamics", spends 37 pages to describe the various means used to define lift, along with the shortcomings of most of them. These pages then finish with his thoughts on how to define lift. This highlights the sheer number of ways that his has been explained.

This book is quite good, but I only suggest it to a serious aerodynamicist.

[Dan Marotta]

On a more serious note, the folks who design and build gliders probably
have a good idea of what creates lift.Â* Why not ask them? Or do you
suppose that they know "how" but not necessarily "why"?

On 7/3/2018 12:38 AM, wrote:
> That article appears to be a reasonable effort.
>
> Doug McLean in his book, "Understanding Aerodynamics", spends 37 pages to describe the various means used to define lift, along with the shortcomings of most of them. These pages then finish with his thoughts on how to define lift. This highlights the sheer number of ways that his has been explained.
>
> This book is quite good, but I only suggest it to a serious aerodynamicist.
>
>

--
Dan, 5J

[[email protected]]

Push forward and the trees get bigger, pull back and the trees get smaller, pull WAY back and they get bigger again. Anything beyond that from a pilot is mental masturbation. I'm going flying.

[Jim[_33_]]

I'm dumb as a post about this stuff. Fortunately it seems I do not have to know HOW lift is created as long as I know that lift IS created - and how to manage it.

I am satisfied that it is differential pressure between the upper surface and lower surface of a wing - and the resulting down-deflecting of a mass of air - that results in the creation of lift. Newton seems to describe the process clearly.

What I have yet to come across is an explanation I can understand of why there is relatively lower pressure across the top of a wing. Maybe it actually is described in the calculus. Unfortunately I can barely balance my checking account so calculus is not accessible to me.

[Craig Funston[_3_]]

On Monday, July 2, 2018 at 11:38:24 PM UTC-7, wrote:
> That article appears to be a reasonable effort.
>
> Doug McLean in his book, "Understanding Aerodynamics", spends 37 pages to describe the various means used to define lift, along with the shortcomings of most of them. These pages then finish with his thoughts on how to define lift. This highlights the sheer number of ways that his has been explained.
>
> This book is quite good, but I only suggest it to a serious aerodynamicist.

[[email protected]]

"They make some of the ugliest planes
in the world, except for the Spitfire, there must have been a Frenchman,
an Italian, or an American involved in that design."

Yeah the French:

https://www.flickr.com/photos/varese2002/15650504868

Italians:

https://en.wikipedia.org/wiki/Stipa-Caproni

and Americans:

https://en.wikipedia.org/wiki/Boeing_X-32

sure design nice aircraft, unlike the aesthetically challenged Brits:-)

https://en.wikipedia.org/wiki/Avro_Vulcan

https://www.baesystems.com/en/heritage/hawker-hunter

As to lift theory all I'm can say for sure is that if someone's explanation of lift begins and ends with Bernouilli and the statement that the shape of the airfoil making the air travel a longer path over the top surface and thus reducing the pressure above the wing is what lets a plane fly, you can probably ignore the rest of what they say.

[[email protected]]

The Handley-Page "Victor" has to be in the running for "Top Dog."

https://www.google.com/search?q=handley+page+victor&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjHtZzLuIXcAhUm24MKHRh6DyEQ_AUICigB&biw=1684&bih=833#imgrc=IUcahnoNfvE-PM:

[john firth]

On Sunday, July 1, 2018 at 10:08:44 AM UTC-4, Matt Herron Jr. wrote:
> Interesting read...
>
> https://www.grc.nasa.gov/www/K-12/airplane/wrong1.html

At the molecular level, try this.

Air molecules have random motions and velocities; they bounce off randomly
at all angles to the surface.

The lower surface is flatter than the upper surface, and more molecules
will bounce off close to normal to the airstream ( the free stream, not the local) than on the top surafce.
Hence more push up than push down= lift!

JMF

Afterthought; maybe heating the lower surface will provide more push
as the recoil will be enhanced. a flat wing with zero AoA, with a hot lower and a cold upper surface will produce lift.
BTW, the flow could be almost 100% laminar.

The student should calculate the power needed for an electric aircraft
to fly using the thermo-electric effect in a flat bi-metallic wing.

[[email protected]]

Just to add to the confusion: this is a video featuring Professor Mike Merrifield (University of Nottingham). Animation by Pete McPartlan.

https://www.youtube.com/watch?v=PF22LM8AbII

The "Sixty symbols" interviews (http://www.sixtysymbols.com/) are some of the best scientific vulgarization videos you'll find on the internet.