# How does a hydrofoil generate lift?

## Bionics

#### Creation of lift due to pressure differences on the upper and lower side of the wing

The incoming air reaches both the longer curved upper side of the wing and the shorter underside of the wing and is then deflected downwards. The air flows faster at the top than at the bottom. Due to the high flow velocity at the top, the dynamic pressure increases. On the other hand, the static pressure must decrease accordingly. On the bottom we have the opposite appearance.
Due to the low flow velocity, the dynamic pressure becomes smaller and the static pressure increases. The static pressure presses against the underside of the wing.

The negative pressure under the wings caused by the slower air flow now generates a force that is only about a third of the total lift. Therefore, the dynamic pressure under the wings is lower and thus the static pressure is higher. Two thirds of the lift is created by the negative pressure caused by the faster air flow on the upper side of the wing. Underpressure at the top and overpressure at the bottom give the total lift. This is at right angles to the incoming air.

Due to the curvature of the wing, a vortex loosens at the rear edge of the wing. Now we have learned from Isaac Newton that actio = reaction. So this starting vortex needs a counter vortex with the opposite direction of rotation. To compensate for this, a flow actually forms in the opposite direction clockwise around the entire wing. Due to the air flowing in from the front when moving forward, the air flows overall backwards, faster at the top and slower at the bottom.

According to Bernoulli's law, there is a negative pressure above the wing and an overpressure below it. The differences in speed generate the lift that pulls the wing upwards against gravity.