Stability for turbulent boundary layer

[alsey42147]

concerning fluid flow past a body, i know that if the boundary layer is laminar then the flow becomes unstable when the Reynold's number of the flow is greater than the critical Reynold's number. is this also true when the boundary layer is turbulent?

tia

 

[russ_watters]

I'm not quite sure what you are asking, but a turbulent boundary layer is more stable than a laminar one. Flow separation is less violent.

 

[Clausius2]

concerning fluid flow past a body, i know that if the boundary layer is laminar then the flow becomes unstable when the Reynold's number of the flow is greater than the critical Reynold's number. is this also true when the boundary layer is turbulent?

tia

The turbulent boundary layer is unstable per-se. In a laminar boundary layer, as the Reynolds number increases, the flow becomes more unstable in the sense than any small perturbation in the flow field ends up growing above the critical Reynolds. The flow becomes unstable, all the perturbations are amplified, and after the transition to fully turbulent boundary layer the flow is unstable but statistically stable. The transition to instability of a laminar boundary layer is described mathematically as the classical eigenvalue problem so called Orr-Somerfeld.