One of the main points I stated as my personal opinion in my book,is that Bernoulli's theorem cannot be applied to phenomena that occur in the air.
When I look it up in various dictionaries, I find that

<Bernoulli's Theorem>
A theorem that demonstrates the law of conservation of energy for inviscid, incompressible fluids in a closed system.
(Only applies to steady flow of ideal gases)

This is how it's written in most cases.

However, "in the air" is not a closed system, and air is not an ideal gas because it has viscosity and compressibility.
Furthermore, air flow through the air exhibits turbulence.
In other words, Bernoulli himself clearly stated that "This theorem does not apply to phenomena occurring in the air."
Why do aerodynamics teachers ignore this?
This theorem does not hold true in an open air environment.

However, because the inside of a pipe is a closed system, this theorem can be used in flow measurement devices by correcting for errors caused by non-ideal gases using coefficients specific to that pipe.

Equation representing the law of conservation of energy

∴ P + (1/2)ρv² + ρgh = constant P: atmospheric pressure, v: velocity, ρ: density,

　 g: gravitational acceleration, h: height

(1/2)ρv² is kinetic energy, and ρgh is potential energy

In level flight, ρ, g, and h are constant, so ρgh can be omitted.

∴ P + (1/2)ρv² = constant.　 In other words, the P term + the v term = constant.

Therefore, the conventional theory is that this equation is interpreted as

　　　　"the faster the air flow, the lower the air pressure"

However, this can also be read as meaning that

　　　　”flow in a field with lower air pressure becomes faster”

but aerodynamics professors don't seem to interpret it this way.

In fact, when explaining various aerodynamic phenomena in the air, it is certainly much easier to explain and understand if we can simply say that faster flow results in lower air pressure.

My book contains several examples that show why you shouldn't use Bernoulli's principle to explain phenomena in the air, but here's just one:

Purse your lips and blow into the palm of your hand.

If the air pressure of the blown-out flow is low, the surrounding air with high pressure should gather and make the flow thinner, but in reality, the opposite happens and the flow expands.

It is a mistake to apply Bernoulli's theorem to events that occur in the air.

∴　this theorem cannot be used to explain the mechanism by which

lift is generated on a wing.

2025.09

Bernoulli's principle does not apply in air.