Aula Teórica 20

Introdução à Camada Limite.Introduction to the Boundary Layer

Flat Boundary Layer

• Inside the BL there is equilibrium between inertia and viscous forces. Outside there is no friction and the Bernoulli equation is applicable.

ij

i

jij

ij

i gxu

xxp

xu

utu

https://www.youtube.com/watch?v=7SkWxEUXIoM

The Boundary layer concept is interesting if it thin

BL evolution• As the fluid moves along x1, the viscous forces

diminish and flow disturbances have a higher probability of not being dissipated and consequently the flow can become turbulent. When we define the Reynolds number, Re, we have to take that into consideration:

Flow regimes

https://www.youtube.com/watch?v=WEX72jeXTGM

Free jet (Jacto livre): Boundary Layer type flow

• There is equilibrium between inertia and viscous forces.

Wake (Esteira): BL type flow

Mixing layer