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How does separation of flow affect pressure drag?
If the angle of attack of a wing traveling through the air becomes too steep, separation of flow occurs. The boundary layer of air moving over the wing slows down because it is forced to move from an area of low pressure to an area of high pressure. When the boundary layer of air slows down to a certain point, it detaches from the surface of the wing and becomes turbulent. This turbulent air has a lower pressure, which has an effect on pressure drag. Pressure drag occurs when air flowing past an object pushes harder against the front than the back. This difference creates a backward force. When separation of flow occurs, the turbulent air behind the airfoil decreases in pressure, causing an increase in pressure drag.