Whenever we ask someone how an aircraft produces lift they are able to answer based on Bernoulli Principle(BP); the airflow above the aerofoil has a higher velocity whereas the airflow on the lower surface of the aerofoil has a lower velocity. Based on BP the higher the velocity the lower the pressure therefore the difference in air pressure produces lift.
When a follow-up question is asked why the airflow on the upper surface is great, a majority of us are unable to answer. So today I will be splitting on Why & How the airflow has a greater velocity on the upper surface.
This is a typical Cambered Aerofoil (Asymmetrical Aerofoil):
Just for your information. Cambered aerofoils are not used in most modern aircraft, Symmetrical and Supercritical aerofoils are used.
To start off, Aerofoil basically uses two principle in producing lift:
- The Principle Of Continuity
- Bernoulli Principle
1.The Principle Of Continuity
The air mass flow, or mass per unit time, through the tube will be the product of the cross-sectional area (A), the airflow velocity (V) and the air density (ρ).
Mass flow will remain a constant value at all points along the tube. The Equation of Continuity is:
A × V × ρ = Constant
For An Example, The Mass Flow throughout Point 1, 2 and 3 is the same.
Which means that the flow of mass is constant throughout every part of the tube. When a same amount of volume passes through a narrower tube the velocity increases whereas when it travels through a wider tube the velocity is lower.