Question

Explain dynamic lift.

Answer 1

Dear Student

Dynamic lift- A fluid flowing past the surface of a body exerts a surface force on it. Lift is defined to be the component of this force that is perpendicular to the flow direction. It contrasts with the drag force, which is defined to be the component of the surface force parallel to the flow direction.

The lift is there because of difference in pressures created by the movement of air in different velocities along the upper and lower surfaces of the airfoil. When the airfoil moves forward with a velocity, the stream of air passing through its lower surface attains higher velocity because of the shorter distance it has to cover while the air passing through the upper surface has a higher velocity. From Bernoulli’s theorem we know that higher is the velocity lower becomes the pressure and vice versa. Thus the airfoil in motion has low pressure on its upper surface and high pressure in its lower surface. This gives the foil a lift.

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