# No one can explain WHY planes fly...

### Help Support HomeBuiltAirplanes.com:

#### BJC

##### Well-Known Member
HBA Supporter
Look up the thread "Lift and Conservation of energy"
Thanks for that reference. I joined HBA shortly after that thread ended, so I just now read it for the first time. It certainly was an interesting discussion. I like your injection of significance:
However.....this is all decimal dust when it comes to homebuilt aircraft.
BJC

#### Speedboat100

##### Well-Known Member
Can Bernouli or Prandtel predict exactly when the stall occurs. That is, when will the flow become turbulent?
No but Prandtl's pupil Blasius did.

#### Monty

##### Well-Known Member
Thanks for that reference. I joined HBA shortly after that thread ended, so I just now read it for the first time. It certainly was an interesting discussion. I like your injection of significance:

BJC
It's definitely a "how many angels can dance on the head of a pin" type thing as far as we are concerned.....but among Aero types (especially undergrads and 2nd year grad students who do nothing but play with databases, airfoils and panel codes)....you can start bar fights with this stuff. They leave their course of study believing they are experts, and having been indoctrinated-angrily strut about pawing and puffing nonsense. They don't know that classical aerodynamics inherited all the bad things from the unholy union of mathematics and continuum mechanics. Most people who teach classical mechanics have the same blind spot. There are clumsy work arounds like the coefficient of restitution or....lift and drag!.....a coefficient is what you use when you don't know what the hell is really going on. Nothing wrong with that...you can build a perfectly usable aircraft with it, or predict how high the ball will bounce. but you should recognize the fact: they should really be called coefficients of ignorance.

It's a religious matter...the immaculate vortex! It flows in one side and out the other conceiving our savior Lift! No heat was needed!! Occasionally the holy inviscid vortex reveals itself to the pure and chosen through a math so exquisite only the divine could conceive or understand it!!....And it manifests in the real world!!!! SEEE!!!! there it goes!!!

Facepalm.....I'm a knuckle dragging thermodynamic heretic. Or at best an experimental aviation agnostic.

Burn the witch!!

#### Aerowerx

##### Well-Known Member
Unless you're an Anglo French consortium, then it's pride.
Uh, Norm.

That wasn't my statement you quoted.

#### Aerowerx

##### Well-Known Member
No but Prandtl's pupil Blasius did.
I doubt it.

I said EXACTLY when the stall happens.

Given Heisenberg's Uncertainty principle and quantum theory as it applies to Chaotic Systems, when you get down to the quantum level things just happen. Or they don't. And there is no way to tell ahead of time if they will. Or won't.

#### Monty

##### Well-Known Member
I doubt it.

I said EXACTLY when the stall happens.

Given Heisenberg's Uncertainty principle and quantum theory as it applies to Chaotic Systems, when you get down to the quantum level things just happen. Or they don't. And there is no way to tell ahead of time if they will. Or won't.
EXACTLY!!! It's not a continuum! and there is no computer big enough to get a solution to the granularity required. And when you did.....statistical thermo and quantum mechanics would be needed....and guess what...every solution would be different!!! SHHHHH!! You're going to upset the church of vortex people...

#### Speedboat100

##### Well-Known Member
I doubt it.

I said EXACTLY when the stall happens.

Given Heisenberg's Uncertainty principle and quantum theory as it applies to Chaotic Systems, when you get down to the quantum level things just happen. Or they don't. And there is no way to tell ahead of time if they will. Or won't.

Okay...let's then say..Blasius predicted how long the flow stays laminar ?

#### Speedboat100

##### Well-Known Member
EXACTLY!!! It's not a continuum! and there is no computer big enough to get a solution to the granularity required. And when you did.....statistical thermo and quantum mechanics would be needed....and guess what...every solution would be different!!! SHHHHH!! You're going to upset the church of vortex people...

It is true...even a light drop of sweat on the surface changes the situation...etc.

#### Monty

##### Well-Known Member
It is true...even a light drop of sweat on the surface changes the situation...etc.
I should point out that I'm picking on engineers a bit here, mostly in jest. While we (I are one) may be ignorant of all the details; the bros Wright constructed a flying contraption while the physicists argued about how it was impossible. Including the likes of Lord Kelvin-the true father of the demon spawn church of the vortex....without even having 1/2rhoV2CL thing totally figured out yet. They just lumped everything into the "Smeaton" coefficient and built the darn thing.

No one should get their feathers ruffled about any of this, but they do....OH BOY do they ever!

#### Monty

##### Well-Known Member
Thanks Mr Monty
I knew that all wind is dissapated as heat, and see things around wind energy where claims are made that turbines add heat, which seems to me impossible.Hadnt thought of lift bieng ultimately converted the same way as friction into heat.
Had to add a clarification here. The Wind turbines don't "add heat" they simply remove energy from the air as it flows past. In doing so there are viscous losses which manifest as local "heat". This simply concentrates the loss/entropy in a particular location. Otherwise it would be spread over a much larger area. The local temp rise is due to this concentration. The same thing happens in a diffuser. Dynamic pressure converted to static in an irreversible way.

Thermodynamics....if only the politicians and voters understood thermodynamics.

#### jedi

##### Well-Known Member
Had to add a clarification here. The Wind turbines don't "add heat" they simply remove energy from the air as it flows past. In doing so there are viscous losses which manifest as local "heat". This simply concentrates the loss/entropy in a particular location. Otherwise it would be spread over a much larger area. The local temp rise is due to this concentration. The same thing happens in a diffuser. Dynamic pressure converted to static in an irreversible way.

Thermodynamics....if only the politicians and voters understood thermodynamics.
So it is true that wind turbines are causing global warming! I thought so.

I will stick with my statement as proven by Boeing Max and reported in the press again "(Boeing Max) Airplanes do not fly".

#### Monty

##### Well-Known Member
So it is true that wind turbines are causing global warming! I thought so.

I will stick with my statement as proven by Boeing Max and reported in the press again "(Boeing Max) Airplanes do not fly".
The turbines work for the sun! It's a conspiracy!!

Apparently Boeing Max airplanes are so densely designed that they mutually attract to the Earth. Similar to the helicopter, which being so horribly complex, is abhorred by mother nature and is repelled by the Earth.

So...yes. I believe you are correct.

#### Speedboat100

##### Well-Known Member
Had to add a clarification here. The Wind turbines don't "add heat" they simply remove energy from the air as it flows past. In doing so there are viscous losses which manifest as local "heat". This simply concentrates the loss/entropy in a particular location. Otherwise it would be spread over a much larger area. The local temp rise is due to this concentration. The same thing happens in a diffuser. Dynamic pressure converted to static in an irreversible way.

Thermodynamics....if only the politicians and voters understood thermodynamics.

Yes Harvard stated 2018 that HAWT type wind turbines would increase global warming.

#### dog

##### Well-Known Member
Had to add a clarification here. The Wind turbines don't "add heat" they simply remove energy from the air as it flows past. In doing so there are viscous losses which manifest as local "heat". This simply concentrates the loss/entropy in a particular location. Otherwise it would be spread over a much larger area. The local temp rise is due to this concentration. The same thing happens in a diffuser. Dynamic pressure converted to static in an irreversible way.

Thermodynamics....if only the politicians and voters understood thermodynamics.
And thanks again that helps a bit to visualize another odd phenominon which is the significant cooling/heating effect in a vortex tube.

Wind turbines exract energy from
the wind,and your discription of the process explains how extrapolating from one derived subset can yield any "conclusion" the authors
agenda requires.

#### dragon2knight

##### Well-Known Member
HBA Supporter
Well then....despite the fun posts, I'm learning quite a bit here, kind of the reason why I posted this in the first place. We've got a pretty sharp bunch around here, thanks for all the input!

Last edited:

#### Aerowerx

##### Well-Known Member
Okay...let's then say..Blasius predicted how long the flow stays laminar ?
Still no., only in a statistical sense.

When you get down to the last molecule, will it go "this" way or "that" way?

Oh, and don't forget. The very act of watching it changes it's behavior!!

#### Speedboat100

##### Well-Known Member
Still no., only in a statistical sense.

When you get down to the last molecule, will it go "this" way or "that" way?

Oh, and don't forget. The very act of watching it changes it's behavior!!

Are you saying the aviation engineers cannot predict/compute the behaviour of air in one molecule accuracy...when it becomes turbulent ? ?

#### Aerowerx

##### Well-Known Member
Are you saying the aviation engineers cannot predict/compute the behaviour of air in one molecule accuracy...when it becomes turbulent ? ?
Yes!

And can't even when it is laminar.

The only thing that keeps you from suffocating right now is that, statistically, the air molecules are evenly distributed. But there is no way to tell where any given molecule will be in 10 minutes.

#### Derswede

##### Well-Known Member
I need a drink. Where is that bottle of North Wilkesboro, NC octane booster?

Derswede

#### jedi

##### Well-Known Member
Are you saying the aviation engineers cannot predict/compute the behaviour of air in one molecule accuracy...when it becomes turbulent ? ?
Certainly I can predict the behavior on one air molecule even though I have trouble spelling both "molecule" and "engineer". I am a glider pilot. I believe it will go up. I know it will go up. I predict it will go up. Now if only I knew when time starts and when to set the T sub zero (To - the initial time).

Now, would you please point out which molecule you would like to use for the subject of this experiment.

PS: And, I don't even know how to correctly type "To" on this computer.

2