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Lift on a wing
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Pressure difference and downwash give lift.
An aerofoil deflects air downward (Newton's third law) and creates lower pressure above than below (Bernoulli). Lift ≈ ½ρv²SC_L, increasing with angle of attack up to stall.
A 747 requires about 250 km/h to take off.
Stall occurs when flow separates.
In more detail
Lift on a wing arises from the pressure difference between its upper and lower surfaces. The wing deflects air downward, and by Newton's third law the air pushes the wing upward.
Real-world uses
- Aircraft wings, helicopter blades and sails generate lift.
- Racing car wings create downforce by the same principle.
- Engineers designing aircraft wings and wind turbine blades use the pressure difference across the surface to calculate lift.
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Frequently asked questions
Is lift just from Bernoulli?
Not only. Lift also comes from the momentum change of the deflected air.
Why does angle matter?
Increasing the angle of attack increases lift until the airflow separates and stalls.
Is lift only from the pressure above the wing?
No. Both the pressure difference and the change in air direction, which is the downwash, contribute to lift.
Related topics in Fluids & Elasticity
Torricelli's theorem · Venturi meter · Pitot tube · Magnus effect · Viscosity · Poiseuille's equation