Question

k) If one says that there is a favorable pressure gradient along a solid surface, one means that the static pressure along the surface is dropping (getting smaller) in the direction the flow is going just above the surface.

TRUE OR FALSE

Answer 1

In fluid dynamics, an adverse pressure gradient occurs when the static pressure increases in the direction of the flow. Mathematically this is expressed as: {\displaystyle dP/dx>0} ${\displaystyle dP/dx>0}$ for a flow in the positive {\displaystyle x}-direction. This is important for boundary layers, increasing the fluid pressure is akin to increasing the potential energy of the fluid, leading to a reduced kinetic energy and a 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.

Therfore, the fluid acclerates in the direction of decreased pressure.

So it's true