Adverse pressure gradient
In fluid dynamics, an adverse pressure gradient is a pressure gradient in which the static pressure increases in the direction of the flow. Mathematically this is expressed as dP/dx > 0 for a flow in the positive x-direction.
This is important for
deceleration of the fluid. Since the fluid in the inner part of the boundary layer is slower, it is more greatly affected by the increasing pressure gradient. For a large enough pressure increase, this fluid may slow to zero velocity or even become reversed causing a flow separation. This has very significant consequences in aerodynamics since flow separation significantly modifies the pressure distribution along the surface and hence the lift and drag
characteristics.
Aeroplane wings are often engineered with vortex generators
on the upper surface to produce a turbulent boundary layer.
See also
References
- McGraw-Hill.
- Hermann Schlichting (1960) Boundary Layer Theory, McGraw-Hill.
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