Adverse pressure gradient - Definition and Overview

An adverse pressure gradient occurs when the static pressure is increasing in the direction of the flow. This is important for boundary layers, since it has the effect of decelerating the flow. Since the flow in the inner part of the boundary layer is already very slow, it can be stopped or even reversed by an adverse pressure gradient. In general, the boundary layer will thicken quickly in areas of adverse pressure gradient, and may separate from the surface.