Bernoulli's principle

But note that in unaccelerated flight (e.g. descending at a constant rate) the wing must produce the same lift that it would in level flight.

This is the classic question that confounds the Bernoulli-only explanation. If lift depends solely on the shape of the wing, there should be no way to support an aircraft when the curved surface is down and the flat one is up.

But planes with wings like that fly inverted every day. So there must be something Newtonian at work.

Pressure involves matter changing direction

A Vector of Newton?

it’s all newtonian–even bernoulli is newtonian :slight_smile:


The same way they can fly right side up.

Velocity at Angle of Attack of the wing creates the Force of Lift. The Force of Lift is equal to and dependent on the Velocity at Angle of Departure (of the air mass from the trailing edge of the wing.

The best shape of the wing is the most streamlined shape for any given airspeed and angle of attack. Flying that same wing upside simply makes it less streamlined. Raise the angle of attack and increase the power to make up for the increased drag and the upside down wing provides lift.

Picture a NASCAR race car. The whole top surface of the car acts as a wing. The speed of the air parallel to the surface of the car provides lift through velocity alone (Bernoulli). Notice the air dams that prevent air from flowing under the car. Unlike an airplane wing, there is no opposing Bernoulli Effect on the car’s underside to counter this Bernoulli Lift. At a certain velocity, a perfectly streamlined care will lift due to Bernoulli’s force alone.

Notice the little spoiler on the tail of the car. Compare the surface area of the spoiler to the whole surface area of the car. The spoiler deflects the airflow upwards. Newton. That tiny bit of Newton not only counteracts the Lift of Bernoulli, it creates enough extra Down Force to press the car onto the track.

The upside of any wing is simply the side deflects the air mass most efficiently. Any wing that can deflect air in one direction can deflect the air in the opposite. Any wing can fly upside down.

Peace through Liberty

Pressure is a Force. Matter changing direction is a Reaction to said Force.

A Vector is the Angle and Carrier of Force. Bernoulli’s formula only applies to Fluids traveling parallel to a surface. All other Force Angles (Vectors) are outside Bernoulli’s formula.

Bernoulli is the carrier of Newtonian Force in Parallel Vector.

Newton describes the Reaction to Force in all Vectors, including Parallel Vectors.


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There is indeed downwash behind a bump in the floor; the downwash dissipates sideways across the floor. A bump in an air stream leaves a wake.

A better example of Bernoulli (lift without downwash) is the wind tunnel floor itself. As the airspeed over the floor increases, the air pressure on the floor lessens according to Bernoulli’s formula. Increasing airspeed over a surface increases lift. Bernoulli.

The key to lift is not what happens to the departing air mass; the key is that the departing air mass gained its downward Force Vector by imparting equivalent Lift to the Wing.

A wing in that same wind tunnel also creates lift. However, the lift generated by a wing is magnitudes greater than the lift generated by the floor. The critical difference is that the attack (Force) of the wing Accelerates air Mass Downward. The wing experiences Lift. Newton.

Again, compare the surface area of a spoiler on a NASCAR racecar to the whole upper surface area of the car. That is the power of Newton over Bernoulli.
rwjefferson – “an unknown amateurdynamicist”

Peace through Liberty

I’ve read Brian Greens’ book you mentioned and it is indeed an excellent read.
Perhaps akin to Paul Davies’ material. which I recommend.


If we have an upwards force acting on the floor of the wind tunnel, then the floor of the wind tunnel is exerting a downwards force on something. If it were the air causing the upward force, then this would be a downwards force on the air, which would cause a downwash. If this is not the case, then what is exerting the force, and why doesn’t it react to the force the tunnel floor is putting on it?

That would appear to be the air beneath the floor, right? Although I wouldn’t exactly call that a downwash.

The Force acting on the floor of the wind tunnel is not acting upwards. The Force acting on the floor is Air Pressure downward. As the speed of the Air Stream increases, the Air Pressure decreases due to Bernoulli-Newton. It is not Pressing down with as much Force as it was when it was motionless.

If there is stationary air above the Air Stream, it will be pulled into the air stream by the Pressure Difference. Areas of differing pressures tend to Equalize.

If the air stream passes beyond a raised floor, there is no longer Velocity across a Surface. The Bernoulli factor of Newton ceases. The Pressure and Density rises. The additional Density is less buoyant than the surrounding air. The Air falls. This results in Downwash. As long as extra air Pressure does not seep under and lift the floor, there is no lift or lift induced downwash.

I hope this helps.