Expert: Paul Soderman - 8/27/2011

Question
QUESTION: From Vidhyasagar

Thanks very much.

My questions in your explanation dated 7/9/11.

1. Your statement:
"These forces do not require collision of the flow with the body."

  These forces are pushing/repulsive forces.
i.
Q1: Does it mean that airfoil air flows apply such forces from a distance without contact with the airfoil? And transfer their work energy to the airfoil from that distance?

Literature doesn't seem to say like this.

ii.
Newton accepts collision.
  (a) On page 6 of Prof.Anderson's book,'Fundamentals of aerodynamics' 4th edition, 2007: ' Newton assumed that upon striking a surface inclined at an angle to the surface...'
  (b) On page 763 of the book under 'Newtonian theory': 'According to Newtonian model the flow consists of large number of particles which impact the surface and move tangentially. During collision with the surface...'

iii.
In sec. 1.10.1 Prof.Anderson accepts collision of flow with body.

iv.
NSSL is a collision law of fluids.

v.
One would have seen many times neutral bodies applying pushing forces only by contact collision. Airflows cannot be exceptions.

Q2: So, is it not illogical to deny or not to consider collision in aerodynamic lifts?

2. Your statement:
" The only way gas molecules gain or lose kinetic energy is if temperature changes"

  It is well known that temperature is measure of average kinetic energy of molecules of a substance. More is the energy more is the temperature. Less is the energy less is the temperature. So, temperature change is a result of gain or loss of kinetic energy not the cause.

  The causes of gain of kinetic energy:
(a) (Mechanical) collision work. E.g. Switch on an electric fan. Air molecules ahead of blades gain kinetic energy and flow as a stream. It is not because temperature changed but because the fan blades did collision work.
(b)By absorption of heat energy. This is adopted in pressure cookers.

 The causes of loss of kinetic energy:
(a) (Mechanical) Collision work. E.g. The wind molecules in wind turbine loose kinetic energy because they do collision work on the blades by which the blades rotate.
(b)
Q3:Is there any other cause?

This again shows that it is illogical to deny collisions.

3. Your statement:
" A wing fixed in a wind tunnel has no kinetic energy but the air stream has kinetic energy."

i. Fact: The free stream becomes faster at the leading edge and attains maximum velocity at a point x ahead of the crest (Sec. 11.6.1 of Prof.Anderson's book).
  It means the free stream gains kinetic energy there.

Q4: From where does it gain this energy?

ii. The only way it can gain kinetic energy is mechanical work on it.
Q5: If the airfoil doesn't have the energy to do work then which body does the work?

4. Weltner's interaction.

Q5: If airfoil doesn't have kinetic energy then which body forms pressure gradients to cause velocity changes in the stream?

5. Your statement:
" Therefore it does not make sense to ask which flow or which pressure causes lift"

i. You have identified a pressure that causes a force on the airfoil by your statement; " At stagnation point the strong ram pressure cause a strong force in the aft direction."

ii. You have accepted that this airfoil, when at +AOA, is lifted by the free stream by NSSL.

Q6: Why can not one identify the body that lifts and the law by which it lifts the airfoil when at zero AOA?

      
6. Your statement:
" Alternatively you could imagine the flow to be entering a venturi between an airfoil surface and the free field (atmosphere) and accelerating."

  This is the 'Venturi effect theory' that has been and has to be rejected for the following reasons (the first two are given by NASA):

i. A venturi requires two solid curved opposing surfaces (to squeeze/compress the stream for acceleration)
  One airfoil surface forms one such surface. But the free field on the other side of the stream cannot form such a surface.

ii. In a venturi, as one goes from a venturi surface to the centre of the venturi the velocity of the stream goes on increasing. But in the airfoil, as one goes from the airfoil surface, the velocity goes on decreasing.

iii. The velocity of the stream goes on changing downstream. It is difficult to accept the presence of curved venturis of varying cross sectional areas adjacent to both airfoil surfaces.

iv. Even if one unwillingly accepts such venturis you have to explain the cause of speeding up of the stream in a venturi. Weltner's pressure gradient due to interaction of the stream and venturi surfaces cannot be the cause because the static venturi does not have energy to form this gradient - as the static airfoil doesn't have.  Other explanations are deficient in failing to answer one vital question: " Which body does the work on the free stream, at the entrance of the venturi, to make the stream faster?"

7. For the lift of the above airfoil while moving at zero AOA in static atmosphere.

Your statement:
" A wing in flight has kinetic energy provided by the propulsion system. This energy eventually heats up the air and the aircraft."

i. You have left an important gap relevant in the explanation of this lift.
Q7: How does the kinetic energy get out of the wing and get transformed into heat energy?

ii. According to Weltner the interaction must be between the moving wing and the static atmosphere.

Q8: Why does the interaction occur only when the wing moves?

There are no air streams over wing surfaces to cause velocity changes.  

Q9: Then what do they cause?

When the wing moves near the ground the lift increases. This increase in lift is called ground effect.

Q10: It means the interaction has changed. Why?

The ground effect increases when the wing moves faster and when it moves nearer to the ground.

Q11: It again means interaction changes. Why?

It is obvious that the explanation of this lift will be different from that when it is stationary and air stream flows across. But surprisingly literature does not talk of this lift at all.

Thanks again.
Vidhyasagar

ANSWER: Vidhyasagar - Another epic question.  Don't you have any short questions ?  

1.  Flow must interact with a body to provide pressures and forces.  It does not act at a distance though the pressure field around a body can be large. In classical fluid mechanics we only require the fluid to flow around the body.  It does not have to bounce off the body like billiard balls.  See the following NASA website for incorrect conclusions that can arise from such action-reaction models:  http://www.grc.nasa.gov/WWW/K-12/airplane/wrong2.html

2.  Anderson's discussion of Newtonian theory applies only to simple, hypersonic bodies and is not correct for subsonic or typical supersonic flows.  See:  http://www.aerospaceweb.org/design/waverider/theory.shtml

3.  You are correct, molecules can develop kinetic energy from heat transfer or mechanical work.  In thermodynamics, heat and work are equivalent or interchangeable.

4 & 5 & 6.  In a wind tunnel, the source of flow energy is the wind tunnel fans.  Along a streamline, the velocities can increase or decrease depending on the flow cross sectional area.  That is, the flow potential energy can be traded for flow kinetic energy or vice versus.  See Bernoulli's law.  It is the pressures in the flow that cause the accelerations or decelerations of flow.  A body can change the flow area or flow path such as the flow over the surface of a wing.  If there is no body, the flow just moves along the duct without change (except for losses due to viscosity).  If a body causes the flow to change direction then in does work on the fluid even if the body is stationary.  The body provides a reaction force that causes an acceleration of the fluid just as a floor does to a bouncing ball.  That reaction force has a lift component.

No, I do not accept NSSL for airfoil lift at speeds less than hypersonic.  Stagnation pressure is the result of the stream coming to rest at the airfoil nose.  Bernoulli's law describes it quite well.

I don't like the venturi explanation for velocities on an airfoil either.  There are much better explanations as I have previously discussed.

7.  The kinetic energy of the wing heats the air and aircraft via viscosity (friction).  High speed aircraft can get extremely hot from air friction.

8.  Question unclear.  Of course you have to have relative motion between a wing and air to get lift.  A wing sitting on the runway has no lift. But this is so obvious I don't understand your point.

9 & 10.  Ground effect is a result of the interaction between the pressure field of the aircraft and the ground.  The ground effectively causes the wing lift pressures to increase.  The mechanism is a little complex for this forum, but you can think of it as a reflection of pressures onto the aircraft.  There is also an upwash that increases the angle of attack of the wing.

11.  Ground effect can be found in certain aerodynamic books dealing with STOL aircraft (Short Takeoff and Landing) or ground effect machines.  It is a well known phenomenon that can be modeled mathematically and can be measured in a wind tunnel.
Paul



---------- FOLLOW-UP ----------

QUESTION: Thanks once more,

Sorry for twice making the mistake of asking too many questions at a time.
This time I have to take the the first two answers because they are related.

So, you agree that a flow cannot act on a surface from distance; so must come in physical contact with the surface for your interaction of Coanda effect, centrifugal forces and Newtonian forces to occur. Commonsense and daily observations tells us so. And neutral bodies cannot apply repulsive forces from a distance. There is also no law that states that they do.

But consider the actual observations given in the aerospace website you have quoted.

  "At supersonic speeds a flow (particles/molecules)collide on a stationary slope (like the leading slopes of an airfoil), apply (collision)force on the surface and then get deflected.
  But at lesser speeds, the flow diverges far ahead of the slope."

This latter observation was first made in 1781 by Leonhard Euler (Sec.1.1, Prof.Anderson's book): '... the fluid moving toward a body, before it reaches the latter, bends its direction and velocity...'

It means the flow's direction and velocity changes without interaction with the slope.

   This observation raised my so far unanswered (in literature)questions

Repeat:

Q1.A super sonic flow collides on a slope. But the same flow at lesser speeds does not collide. Why? What prevents it from colliding?

Q2. Which body applies the force to change its dirction before it reaches the slope? (Newton's first law question)

The flow actually becomes faster over the slope. It means a force does work on it transferring energy to the flow i.e the point of application of the force on the flow moves. The force must be in the direction of the flow - a force on it from the opposite direction will slow the flow.

Q3: Which body does this work on the flow in the direction of the flow before the flow reaches the slope?  

Q4: At the leading edge of the stationary airfoil, how does the very strong stagnation pressure, causing the strong aft ward force on the airfoil (pushing the airfoil aft ward - the drag) develop?

Vidhyasagar

ANSWER: Vidhyasagar
I think you are getting confused by the word 'collide'.  In kinematics, we often say that one body collides with another and is deflected away.  But in aerodynamics, when we say the flow is deflected we mean that it changes its momentum or its velocity (speed and direction) by flowing around a body, but it does not deflect away from the body as simply as it does in kinematics.  Usually the flow stays attached to the body as long as possible until it separates and moves in a direction that may be different than the oncoming flow.  See http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html. So to answer your new questions:

1.  At subsonic speeds the body interacts with the fluid to create a pressure field that radiates in all directions.  The pressure fields causes the oncoming fluid to change directions so that some fluid starts to move upward over the body and some moves downward to pass under the body.  One streamline actually collides with the body at the stagnation point and the fluid is stopped.  On the upper and lower surfaces of the body the flow does contact the surface.  We usually call that an interaction, not a collision, but the net effect of all the interactions is that a mass of air is deflected downward if the body is an airfoil at angle of attack and lift is created on the airfoil.  Both upper and lower surfaces are important to the momentum change and lift.

The same thing happens as supersonic speeds except that in the upstream direction the pressure field is stopped at the shock waves.  But as the air flows through the shock waves it once again can interact with both the upper and lower surfaces to create lift and drag.

It is only at very high (hypersonic) speeds that things get a little bizarre because the flow interacts so much faster with the lower surface of a thin airfoil than the upper surface that alternate theories must be used (see http://www.aerospaceweb.org/design/waverider/theory.shtml).

2.  The body interacts with the flow to create pressures.  Pressures are forces and cause the flow to accelerate or decelerate along a streamline. The direction of fluid motion depends on pressure gradients; the fluid moves from higher pressure to lower pressure regions. This happens throughout the field and is not restricted to the flow that is in contact with the body.

3.  See answer 2.

4.  As the flow approaches the stagnation point, it feels the pressure increasing and it slows down and finally stops at the surface.  All the kinetic energy of the flow is traded for potential energy in the form of pressure. That high pressure at the surfaces creates a strong force on the body mostly in the drag direction. To keep the airfoil flying forward, something such as a jet engine must do work.  So in the big picture there is conservation of energy, momentum and mass relative to the fluid and aircraft (or boat, or car...).

Vidhyasagor - you have asked many times about what body does work on the flow.  If we have a simple wing in flight, it is the wing that does work on the fluid using energy provided by the propulsion system.  I don't understand your confusion on this point.
Paul



---------- FOLLOW-UP ----------

QUESTION: Thanks once more.

1. Your last statement:

“Vidhyasagar – you have asked many times about which body does work on the flow. If we have a simple wing in flight it is the wing that does work on the flow using energy provided by the propulsion system. I don’t understand the confusion on this point”

My question was for the flow in the lift of the stationary wing which does not have kinetic energy to do work but still the work occurs. But you are answering again and again in terms of a moving wing which has kinetic energy to do work.   

In the case of the moving wing there is no air flow for the wing to work on. It moves in static atmosphere. Only in the lift of the stationary wing there is the free air flow (in wind tunnel experiments sent by an electric fan) and its flows around the wing.

I don’t understand why you miss these simple points of differences.

2. The two lifts are not same (I have shown it for the lifts at positive angle of attack). But aero-experts have been making this mistake - taking observations, energy and force of one lift to the other and explain many things – repeat many things - which they cannot explain in one lift. My aim is to correct this mistake.

3. Let us examine the created interaction pressure field.

3.1. What kind of force field is this? ,Mechanical force field? Electric force field? Magnetic force field? Inter-atomic force field? Inter-molecular force field?  Nuclear force field? etc.

Please note that your ‘centrifugal forces and Newtonian force” of interaction are not kinds of forces. Verify.

3.2. How far does the created field extend?
To infinity like the gravitational field?
Or extends only between the airfoil and the air stream?
Or extend to a finite distance from the body piercing through the streams around the wing? If so, how far is this distance?

Importantly, is the field present inside the airflows around the stationary wing?

3.3. Can the inter action occur from a distance; If so fromt what distance, I mm, I m, 10m, 1000 km…..?   

3.4. Do you have well confirmed experimental proofs for all these questions?

3.5. Since the bodies involved are neutral bodies the field can only be a mechanical force field. If so, this field, which does so many things given below, would have been mentioned, studied and quantified in mechanics and should have been in aerodynamics. But it is not. Verify.

4.1. Let us see the forces this field applies to cause accelerations in the case of the stationary fixed wing (in wind tunnel experiments):

= At the leading edge it turns the upper part of the free stream upward and backward but somehow always knows to turn the lower part downward and aftward, never in any other direction – or first form pressure gradient - where, in the free stream or the branches or it has the gradient inside it ? – so that the free stream turns – using which energy to form the gradient?

= At the leading edge, it also speeds up both the branches supplying energy to them, from where it gets energy continuously?(note - the stationary wing does have energy to give to it).

= It never forgets to speed up the upper branch faster than the lower branch applying more force on the upper part of the free stream supplying more energy to it.

= It always speeds up both the branches only up a point x ahead of the crests of the wing after which (over the same slopes) it begins to go on applying forces in the opposite direction to gradually slow them down - ? taking their kinetic energy – by what mechanism this mechanical energy transfer occurs?

= In the meanwhile it applies a downward force at the crests to turn the branches - ? by forming a pressure gradient.

- All these accelerations on its one side.

On its other side:

It applies forces on the surfaces of the wing all around.

But at the leading edge it applies a net aftward force.

On the under surface it applies a net upward and backward force to lift, never in any other direction.

It always knows never to apply a net downward force on the upper surface to push the wing down.

When the wing is near a liquid or solid surface it applies a greater lifting force – the ground effect - (? can only be due to the interaction of the wing and the lower branch with the ground), using more energy – getting from where, I can’t guess.          

Very efficient and intelligent field, isn’t it? OR

- It causes all these accelerations of different magnitudes, directions, at different places very accurately every time and everywhere. It means it does so by some nature’s laws. Which laws?  

4.3. Newton, Euler and later many experts, even present day aero-experts including NASA and the aerospace website experts you quoted, experts in physics, mechanics do not say (even once) that a pressure field is created due to interaction between two neutral bodies like the wing and the air stream and that the field only accelerates the bodies by its forces.

5. So, this time I request you only one thing: Verify the following statement with physics, mechanics experts because it is true in all engineering fields including aerodynamics.

“A moving neutral body like the free stream will apply a collision force directly on a surface in its path like leading/windward surface of the stationary wing without creation of a pressure field i.e. the body/ free stream molecules will only apply the force by collision, not the created field.”

If the experts disagree with this statement I will stop troubling you further.

Vidhyasagar



The following is only for your careful consideration. I leave to your goodness to answer the questions in it.

6. That the free stream will apply a collision force on the stationary wing without the creation of the field can be logically derived from what chemistry books say.

(i) “Gas molecules, traveling in all directions randomly in many velocities, collide on surfaces in their path – surfaces of other molecules and of the (solid) walls of their container - without creation of a pressure field. And apply collision forces – the pressures of these forces we want to measure.”

(ii) After collision they get reflected (due to Newton’s reaction forces to the collision forces.)

(iii) And reflected in the same velocity, so with the same incident kinetic energy i.e. the collisions are perfectly elastic collisions.

The logic:
If gas molecules collide and apply collision forces without creation of an electric field, then an air stream, which also contains traveling gas molecules, will also collide on a surface in its path and apply collision force without creation of a pressure field; and after collision will be reflected in the same velocity.

What is wrong in this logic?

Note:

(a) The molecules are not reflected in higher velocity with higher kinetic energy from the fixed stationary walls.  It will mean the fixed/stationary wall supplies energy to them. Then the velocity, the pressure, the kinetic energy and the temperature of the gas will go on increasing, which never happens.     

(b) There are no pressures (so no mechanical pressure field) present in the spaces among the molecules like e.g. the electric field present in all the spaces among electric charges. To derive equations (to quantify) scientist assume that they are present and also assume that they vary continuously from point to point (for a gas in equilibrium) in the spaces (then only equations can be derived using differential calculus). This is the ‘continuity theory’. Not only pressure, other state properties like density, temperature are also not present at all points in a gas volume. So they use this theory for them also.   

7. Your statements:

“The pressure field causes the oncoming fluid to change direction…”

“ Pressures are forces and cause the flow to accelerate or decelerate….”

NASA website http://www.grc.nasa.gov/WWW/K-12/airplane/presar.html statement:
“The (mechanical) forces are transmitted through the pressure.”

A body only causes/applies a force on another body. This is an irrefutable fact.

Pressure is a kind of measurement of a component of the applied force = Perpendicular component of the force applied / area. It is not the actual force acting.  Being a measurement, it cannot apply/transmit a force.

So, a reasonable statement is, force causes pressure. But the converse is a bad statement. It is similar to the sayings, velocity (= displacement/time) causes displacement, density (= mass/volume) causes mass.

Mechanical forces are transmitted to bodies through contact collision, not through pressure or a pressure/force field. Verify this with mechanics experts.

8. Your statements:

“One stream line actually collides at the stagnation point and the fluid is stopped. On the upper and lower surfaces of the body the flow does contact the surfaces. We usually call that an interaction, not a collision.”  

Your later statement:
“As the flow approaches the stagnation point it feels the pressure increasing and it slows down and finally stops at the surface. All the kinetic energy is traded for potential energy in the form of pressure”.

(i) Contradicting yourself – the airflow towards the stagnation point collides or not?

Another contradiction: So far you have been refusing collision, now accepting collision. If so, you must also accept collision force and its laws.

Another: Contradicting Euler and the aerospace website experts you quoted and many others who say:  The flow does not come in contact - with at least the leading surfaces of the body - but changes direction and velocity before coming in contact.
Based on this observation, Euler even derived an expression for the free stream’s force on slopes, which all have accepted. (Refer sec.1.1. Prof.Anderson’s book)

Who is correct, yourself or Euler et all?
(ii) If one stream line collides why doesn’t all the rest of the free stream?
(iii) Does the colliding stream line interact and create pressure field?
(iv) If one stream line (molecules)’ contact is called collision why not that of others on either side of it?   
(v) Your statement in an earlier correspondence: “The stagnation pressure causes a strong aftward force”

Pressure is a measurement, so cannot apply a force. Here either the airflow or the field or both can only apply. Which is your choice?

(vi) The stream line/s (molecules) stop at the stagnation point (without getting reflected) means that the molecules come to rest?

It could only mean this only because of your later statement “All kinetic energy is traded for potential energy” - because potential energy is the energy of bodies at rest.

If so, it means the colliding molecules make perfectly inelastic collisions. No text book says that gas/air molecules make such collisions against solid surfaces. What is the peculiarity of the airfoil surface at the stagnation point to make such collisions?  

And please refer to a physics expert – The kinetic energy of the flow (given by the electric fans of wind tunnels) will not be traded/converted to potential energy.  

(vii) Why does not the rest of the free stream feel this increasing pressure and stop at the rest of the slopes and trade its kinetic energy with potential energy? - Instead why does it flow upward, downward and aftward?

Vidhyasagar.

Answer
Ah Vidhyasagar - where to begin.  You have some strange ideas.  You state:

"Pressure is a measurement, so cannot apply a force."  By definition, pressure is force per unit area so whether I measure it or not it exists.  Just put your hand out of a car window at high speed and you will feel the force.

In the beginning of your question you seem to ask how a wing in a wind tunnel can do work since it has no kinetic energy.  The work is done through drag.  Through viscosity, the wing takes energy from the air and would slow the airflow if it were not energized by the wind tunnel fans.  In fact the power (work per unit time) absorbed from the stream is the product of drag and airspeed.  The lift force is perpendicular to the flight direction and does no work.

You ask about the pressure field around a wing.  The field is mechanical in nature as it derives from one fluid element pushing on another.  It can extend to large distances depending on the pressures on the wing and the direction.  The field becomes very weak by a few wing chords except in the wake which can extend for many kilometers.  Pressures around a wing have been measured many times in wind tunnel studies, which can be found in the literature.

You ask about the laws of fluid mechanics.  I would say they can be found in any aerodynamics book.  Search on Navier-Stokes, Euler, Bernoulli, Helmholtz, Prandtl, etc.   They explain in great detail how a body can create pressures in a stream.  (I don't know what a 'neutral' body is.)

In statement 5, you ask for verification of the following statement:

"A moving neutral body like the free stream will apply a collision force directly on a surface in its path like leading/windward surface of the stationary wing without creation of a pressure field i.e. the body/ free stream molecules will only apply the force by collision, not the created field.”  That statement is hard to understand.  I think you are saying that a free stream can only apply a force on a body by colliding with it.  In aerodynamics, we would say that the stream interacts with the body to create pressures on the body (forces) and the pressures radiate outward to affect the stream.  That seems simple enough to me.

In section 6 you state:
"If gas molecules collide and apply collision forces without creation of an electric field, then an air stream, which also contains traveling gas molecules, will also collide on a surface in its path and apply collision force without creation of a pressure field; and after collision will be reflected in the same velocity."  Imagine a flat plate perpendicular to a moving stream.  If the stream were comprised of one tiny element of air somehow isolated from all other air elements, it would bounce off the plate with equal and opposite velocity.  But if the air element were imbedded in a stream of elements, the usual situation, it would try to bounce back the way it came but it would run into the elements behind it and would be seriously slowed.  The interaction causes a pressure field that forces the oncoming air to flow around the plate.  At the plate, the collisions might be elastic at the microscopic level, but would be almost inelastic at the fluid element level.

In section 7 you state:
"Pressure is a kind of measurement of a component of the applied force = Perpendicular component of the force applied / area. It is not the actual force acting.  Being a measurement, it cannot apply/transmit a force.  So, a reasonable statement is, force causes pressure. But the converse is a bad statement. It is similar to the sayings, velocity (= displacement/time) causes displacement, density (= mass/volume) causes mass."  This is a bizarre idea.  Pressure is simply force per unit area.  So there is no cause and effect - they are essentially the same thing.  A measurement is not required.

OK - pressures and forces have one big difference. Force is a vector quantity. Pressure is a scaler quantity.  That is, pressures act in all directions.  But when they encounter a surface a force is created that acts normal to the surface. Conversely, if I had a closed cylinder with a piston on one end and applied a force to the piston it would increase the pressure.  The pressure inside would put a force on the piston equal to the force applied.  So pressures create forces, forces can create pressures.  There is only one way we get pressures to act in a unique direction, and that is by creating a pressure gradient in a fluid.  In that case, the flow moves from high pressure to low.

In response to section 8 - Yes, at the stagnation point on an airfoil we can say that the airflow collides with the body.  But everywhere else, the surface flow is parallel to the surface (except in separation regions) so we say that the flow interacts with the surface to create pressures.

Relative to 3.2, the pressure field around a fixed wing in a wind tunnel is identical to the pressure field around a flying wing neglecting minor effects of wind tunnel walls.  This is why wind tunnels have worked well for us around 100 years and give results consistent with flight test if the simulation is accurate.

Relative to 4.1, in a wind tunnel the stream contains kinetic energy and has momentum.  To change momentum (i.e., speed or direction) we only require that a pressure gradient exists in the field that acts on the fluid elements. So now we have a mass and a force. Newton's law does the rest.  Your questions about where does the energy come from in a wind tunnel to cause the flow to change direction is answered as follows:  the wing induces forces (pressures) in the flow which change the momentum of the flow which may or may not result in a change of kinetic energy.

In section 2 you seem to believe that wing lift generated in a wind tunnel is not the same as lift of a wing in flight.  In fact, you propose to show the experts wrong in that regard.  I refer you to a paper I wrote:  Soderman and Aiken - Full-Scale Wind-Tunnel Tests of a Small Unpowered Jet Aircraft with a T-Tail.  NASA TN D-6573, Nov 1971 (see fig. 18).  That figure shows excellent agreement between large-scale (40x80) wind tunnel aerodynamic data and flight test data.  You will have difficulty disproving those results.

Your other questions were either too convoluted or I just got dizzy thinking about them.  Good luck.
Paul