Doug McLean | Common Misconceptions in Aerodynamics

This is the video all those insufferable Dunning-Kruger "minor quibblers" need to watch. Of course they're not gonna, and even if they did they don't have diff eqs down so they wouldn't really learn anything.

You need to use the term excellerate instead of the term push. You put 'excelleration rate' into a lift equation. You don't have a 'push rate'. "Push" doesn't describe "excellerate".

Guess I’ll have to get the book

I’ve been trying to locate total wake downwash visualizations but haven’t found good ones. The focus is always on the things that are easily visualized

I thought it was the wingtip vortices got obstructed by the ground changing the preffure of lift/reducing induced drag 😮 now I feel like I know as much as how do wings create lift? And then after explaining 3rd law and bernoullis, someone asks me so how does a paper airplane produce flight 😂

Wusste nicht, dass die Amis „Schadenfreude“ eingeenglischt haben

As an aspiring airline pilot (no engineering background), I find a lot of these ideas and misconceptions very fascinating. One thing that I wish he elaborated on was his statement at 21:10 where he says, “Viscosity and Coanda Effect are not need. Flows follow convex surfaces just fine without either of those.”

What are the reason(s) for why that it is in layman terms if it isn’t due to viscosity and Coanda?

Thanks for sharing the presentation through! Still finding it helpful in 2025.

Pointy does not mean faster...

Money! $$$
Cash is what keeps jets in the air.

The "push back" seems more intuitive if you think about molecules amd electrons and the difference of potential doesn't it?

Maybe im just too inexperienced

@36:52 is he hinting at a PRANDTL bell shaped wing Lift Distribution curve?

35:00 You can affect the flow structures ahead by placing some device behind it.
For instance, cyclists get a significant efficiency gain if followed by a car, and the car does not need to be that close to the cyclist.
Another way to visualize it is to watch the water flow on rocks in a river. A big area of flow ahead of the rock is affected by it.

I am not saying that the invention is question works... far from it. I am simply saying that you can indeed "affect vorticity over there by placing something over here", as McLean put it.

Very nice sir. Although it would be even more awesome if you derived and, from the equations showed what is wrong and right regardless if you increase the number of lectures

A wing acts to excellerate air downward which causes an opposite reaction called lift.

The alternative title of the talk, An Argumentative Aerodynamicist Gets Old and Cranky and Takes Issue With Just About Everyone, hooked me from the outset.

Could someone please clarify? Is Doug McLean (from 44:55 onwards) saying that flight is not possible without a solid ground somewhere below the airplane? That the airplane (through the atmosphere) effectively presses on the ground over a large area in order to sustain its flight?

It's rather simple, really: momentum conservation explains 100% of the lift and drag on a wing... but it's all by itself not sufficient to calculate the absolute sizes of these forces. Neither is Newton's second law, of course. He mentioned thermodynamics for a reason. Real fluids have internal degrees of freedom which lead to energy loss that goes beyond the dynamics of the fluid.

A rocket is sharing compressed front air equally and hence wings only guid it

When body pass the air it is compressed releasing it over a slanding cone it support from bottom and reflected over cone at slope. Compressed air at below carry the mass

30 years in industry as an aero engineer and this guy almost slipped me into a coma... Omg... Snore!

Trump: “WRRRRRRONG”

Aren’t the almost vertical winglets on modern aircraft supposed to reduce vortices ?

@40:46 - “It’s an axis symmetric integration after all”
…Yea OK right…I bet you say that to all the girls !

Right away, i have a problem with parcels of air. I understand this is trying to break things down into analytical units, but air isn't packaged in units. Anyway, i an 17 minutes in, and so far, I've only heard 'cranky' unsupported bashing of standard principles in physics. Looking forward to the meat of the matter. But I'm wondering if this guy may be behind Boeing's poor safety record of late 😊

Ok, I am hearing nonsense right away. I just finished detailing some of these errors in a related video. I need a break. I'll be back.

finally an explanation...

Professor McClean should be considered a national treasure. As a technical fellow at Boeing, I can only imagine how much he contributed to the advancement of military and commercial aviation aerodynamics during his tenure there. I’ll bet Boeing had a difficult time finding his successor. I get the feeling that colleges aren’t graduating a lot of students with a bent toward applied physics.

Terrible video. Poor teacher; don’t take an arrogant dismissive attitude toward “misconceptions” and then just use a bunch of mumbo jumbo technical terms on slides and then conclude everyone is an idiot.

Good teachers that transcend professional understanding are rare. This guy isn’t one.

Since I first found this video many years ago I've watched thousands of other YouTube videos, and I still regard this as one of the true gems.

Correcting some of his errors:

1)More stream tube pinching over the top than the bottom can't be explained:

Solution: The stagnation point being below the chord establishes the mass flow separation boundary beneath the wing. This positioning causes the top geometry to present greater restriction to mass flow compared to the bottom.

2)Mass conservation doesn't address the cause of the force creating acceleration of flow:

Solution: The path detour shaped for deprivation tends to stagnate mass flow, thereby creating a lateral pressure differential sufficient to sustain a higher flow speed.

3)Lift is too complicated to be explained briefly in a meaningful way:

Solution: A solid asymmetry in a flow field generates an asymmetric resistance to mass flow rate. This asymmetry induces a corresponding pressure/speed response asymmetry consistent with the conservation of mass flow rate and conservation of energy. The resulting transverse pressure difference creates a conservation of momentum reciprocity between the airfoil and the flow field, which represents the force of lift (Newton's 3rd law: change in vertical momentum of flow).

i would have fallen asleep if i was present at this lecture.

Great material, thank you!!!

The school that explicitly stated that they did not trust their own students of engineering to repair a sidewalk on the campus when I suggested to them that their students apprentice with the subcontractor.

I am a microbiologist...I don't know why I like this.

I am watching in March of 2025. After a day of listening to traitorous felons (my own fault) destroying the greatest political construct of human history, this is the most marvelous reaffirmation of the human pursuit of truth. I am forever in your debt, thank you.

28:03 isnt this is just the drag?

1:18 I hope your flying on better airplanes now.

Lift is created because of dollars. The more dollars the more lift you can generate.

36:22 like a boat wake

No action at a distance??
Electron repulsion IS action at a distance!
That is incompetent advice.

I am a physicist who sometimes teaches airfoil theory. You stated in 48th minute that Coanda effect has to do with viscosity. It is NOT a viscous effect (that's a wrong explanation in wikipedia and other places). In my view, Coanda effect is all about the curl v = 0 away from negligible boundary layers, and IT IS the proper explanation for the lift force (Bernoulli law is also needed; curl v = 0 explains why the velocities along the upper surface differ from lower surface, due to non-zero circulation)

I read that book in college

Boeing.................smh...........

There are no explanation of how lift is created. Just talking about that some assumptions were considered wrong

Another big flaw in this?: "Claims of more stream tube pinching over the top, cannot be satisfactorily explained " so, invoking stream tube pinching is stated to somehow be an invalid key factor for explaining lift.

The above is not a convincing disclaimer. What is lift if not the geometrical asymmetry of a solid with respect to the relative wind, causing the relative wind to turn?

What is the most intuitive result of the solid's asymmetry on the relative wind in its vicinity, as far as the comparative effect between above the airfoil vs below the airfoil?:

"Stream tube pinching"

If there is a more constricted flow passage "window" above than below the wing due to the asymmetry, what else would you expect, given the constituent variables of a typical mass flow continuity equation?

So, 2 key pillars of his "Misconceptions" hypothesis (mass conservation as a justification for the force of acceleration, and "stream tube" pinching - acceleration due to mass flow rate conservation through an increase in constriction) seem very thin arguments.

His biggest flaw?: "Mass conservation not a direct reason for acceleration"

If the mass flow is delayed, a pressure gradient is the immediate consequence, which increases acceleration necessary to maintain mass flow rate (sufficient to halt the pressure gradient from expanding).

How can the above be wrong??

He sure bases a lot on implying the above is wrong.

This odd point of his even makes it, prominently enough, into the Wikipedia entry for lift (force).

Something has got to give!

😂😂😂😂😂