I think this is not a case of conflicting theories but of two ways of looking at the same principle were some people think only one way must be correct. However in physics often both ways of looking at things may be correct. It is even one of the delights of engineering. Sometimes a problem can not be solved by force equations (or just after many complex calculation) while the problem becomes really simple when handling it from an energy point of view.

Analogue example :

A car accelerator is pushed down which increases the pressure in the cylinder because more fuel is burned in it. The higher temperature causes the pressure to rise. Now this extra force is transmitted to the drive shaft and converted into a moment. This is then put through to the wheels which press puss the car harder along so it accelerates to a new velocity which is determined by the magnitude of the extra force and the time it is applies. (there are other factors but those will make the example too complex)

A skilled engineer can determine the end speed from this.

However a smart engine (or a lazy one) just asks the amount of extra spend fuel and the overall weight of the car and equates the amount of spend fuel times the know efficiency ratio of the engine to the engine build up in the extra car speed. He solves this equations and knows the end velocity. No need for complex calculation taking into account the gears and different radiusses of shafts and wheels.

Does this mean that a car is not accellerate by force by rather by spend energy ? Of course not. THe energy view is nothing more than a higher abstracted way of looking at physics at work and it is intimately tied to the force view.

The same can be said by this discovery of how a wing works.

By changing the view (moving with the wing, not moving with the wing) the describtion of what happens changes and sometimes this can change alot. This however does not mean that the describtion that is linked to the OTHER point of view/reference is incorrect.

The rest of the article disproof things that the author himself postulates and that most engineers will regard as an accurate describtion of common (eductated) believe anyway.

One claims that their is no suction on the leeward side at all but it is rather a lower pressure than the ambient pressure that is present there.

This is a naive discovery as negative absolute pressures (HIS interpretation of suction) does not exist in the universe
.

Zero pressure is the absolute void. You can never encounter sub zero pressures. Therefor suction is nothing more than a common name given to all pressures lower than a reference pressure (often the ambient pressure). His discovery is therefor a discovery of his own misinterpretation rather than a new insight into the way lift is produced.

One other article attacks bernouilli. This is unfounded. Although I share his view that Bernouilli is not the he sole explaination of the suction on the leeward side I do refer to Bethwaite for the paramount importance of bernouilli is the operation of efficient wings shapes. Bernouilli is very important in explaining the low drag characteristic of shaped wingsections. It is the reason why proper leading edges are so important.

With regard to upwash and downwash ; yes that is the right describtion from a stationairy reference point while a wing passed. It explains where the energy of the engines of a plane is partly dispensated too. We sailors allready knew of these downwashes as we call it dirty air. Ever found that you can't point as high when overtaking another boat to luff in close proximity. It is the downwash or rather windwardwash that gives you the appearance of getting a header.

You can compare this view to the energetic view of the car. In an analogue way.

HOWEVER, this "new" view (which is not new at all as it is taught in universities for some time now) does not say that their is no suction on the lee side and a overpressure on the luff side just as the "old" theory. In fact it does arrive at the same pressure situation as the "old" theory, it therefor does not conflict or contradict with the old theory. SO it is not one or the other but rather both simultaniously and intimately linked and it is dependent on your reference point (stationairy or moving with the wing) which one is dominant.

With regard to Bethwaite, He has written a book that is intended to be understandable to less educated readers. He something makes concessions for this reason. HOWEVER his describtions are correct in basis and he has been lightyears ahead of all most of us. He was one of the sailors who rediscovered that low speed wingshapes behave differently than high speed wingsections and that was a major happening. All his describtions are made from a "moving with the wing reference point". Here the individual particle theory has no merit even though it is there.

DHO, Pressure, density, volume are linked. A rise in pressure is accompanied by a rise in density or volume for a given quantity of fluidum. They are all part of the same set of equations and will never contradict eachother. With regard to your equation, they way it must be applies and the magnitude in which it helps you is very dependent on how you draw your system boundery (enclosed volume)

Of course Bernouillis law is close linked to these pressure, density, volume laws/equations. Also in the energic sense. Meaning, without out side force (a piston) a fluidum can only accellerate when it's pressure is lowered. Energy stored in the presssure is transformed into speed and visa versa. Therefor a speeding up of the airflow is ALWAYS accompanied by a drop in pressure. The articles are right in the respect that not all of the suction is caused by a accelerated flow. Part of it is also caused by angling to flow into a more downward/windward direction.

To my the partical stationairy viewpoint theory is nothing more than a higher abstracted different view than the moving with wing reference viewpoint. Both describe the same principle and explain the same pressure differences.

I hope this makes sense.

Wouter