Is circulation real?

Because there is a lot of boundary effect in the wind tunnel section filmed in the video. Also, the angle of incidence is greater than 15°, and you will have a lot of difficulties in using this video to prove anything or its opposite. So, If you're talking about an experimental proof that the flow speed increase on the upper surface of An airfoil. Just read the study I gave. If you're willing to discuss the air speed around This airfoil in This windtunnel in This video.... I pass... Have fun...

 

Which one?

 

The attached document in post #406, where it is described the Particle Insemination Velocity technique (PIV). It's a technique that allows a direct measurement of the air flow.

 

I also attached a document extract from an internet website that has been on the web for a long time. I don't know if this site still exist today. Anyway, one can find in this document a very small an concise explanation of the "Momentum Theory of lift". Sailor AI will perhaps find some similitude with his "Swept Volume Theroy" that he wishes to be get complete.

 

If you agree that the flow velocities on the upper surface are greater than on the lower surface, then you should accept that they are the cause of the pressure differences and the lift.

The speeds relative to the freestream make no difference. One way to see this is to rewrite the the pressure & velocity relations as
(Cp_upper) - (Cp_lower) = -(V_upper - V_lower) * (V_upper + V_lower)

I think it is most common for the upper-surface speeds to be greater than the freestream. On my graph in post #412 they are for about 90% of the surface, but other foil shapes could have much smaller percentages and it would do nothing to shake the foundations of aerodynamics.

 

Formula should be: (Cp_upper) - (Cp_lower) = -(V_upper - V_lower) * (V_upper + V_lower) / V ref ^ 2
where V ref is the reference velocity used to define the pressure coefficients

 

You're right, of course. I was being sloppy and assuming the velocities were already normalized by V ref, i.e. treating V ref = 1. The same applies to the velocity distribution shown in post #412.

 

Can I infer from this that you agree that in the Babinsky experiment, whilst the upper-surface speed is clearly greater than the the lower surface speed, the upper-surface speed is probably not greater than the freestream?

 

No.

 

I was hoping for better than that.
So how do you account for the contradiction I pointed out in my graphic?

 

Re the above, you did not address part of my previous post

"Take the line A - B, in the upper photo, at all points as you rise from B to A the line moves to the right.
However in the lower photo the line has become "S" shaped. The only way I can visualize that happening is for the bottom half of the air accelerating relative to the upper half thus creating the bulge."

If you look at the Babinsky video prior to the smoke reaching the wing, at 0.32 and 0.35, the top and bottom are significantly ahead of the middle.
That is to be expected if you place an obstruction in a wind tunnel.
It would need a large speed increase for the air to make up the deficit.

 

I haven't forgotten.
In order to move this on from arguing how many angels can stand on the head a pin (q.v.), I am developing a simulation of Babinsky's smoke using @Doug Halsey's velocity distribution in post #412.
Fortunately the laborious task of digitising the diagram was facilitated by it being presented on a regular grid which I am feeding into my PHP scripted simulator.
There I am time slicing the smoke's progress in small enough increments to sample each of the velocity values for the upper and lower smoke streams and the freestream.
Progress is steady, should be done in a couple of days.
Here are some screenshots.

I'm working on the lower surface smoke trail and scaling the length of the smoke to account for the speed difference between the front and the back of the pulse.

 

Could I ask you to nominate the one text that in your opinion best explains the foundations of aerodynamics please?

 

All materials are compressible. We use arbitrary limits to define solids, liquids and gasses. However, the strain can be insignificant and therefore can be ignored. This is valid for any physical state.

 

I think that the argument about where, if and how much the velocity of the flow changes can be easily demonstrated by a simple experiment. Instead of using a continuous source of smoke, evenly spaces puffs would show velocity changes by their relative positions.