#### SpaceShipNine

##### New Member

The overhead question is: Why does air separate from laminar flow to turbulent flow as we increase the AOA?

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wiki:

**Flow separation**occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer falls almost to zero.

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wiki:

An

**adverse pressure gradient**occurs when the static pressure increases in the direction of the flow. This is important for boundary layers, since 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.

SpaceShipNine: what does this mean? are we increasing the Potential Energy of the fluid when we increase the AOA? If so why?

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wiki:

**Reynolds number**Re is a dimensionless number that gives a measure of the ratio of inertial forces (

*L*)

laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion, while turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce random eddies, vortices and other flow fluctuations.

SpaceShipNine: How is increasing the AOA changing the Reynolds number? If im close in my understanding, increasing the AOA means increasing the inertial forces that slows down the boundary layer, until it slows down to a point and it just... separates?

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I think I just got even more confused trying to ask this question...