How can you tell at which point the flow transitioned from laminar to turbulent on an
1 Attachment(s)
ok I just have one basic question here... How can you tell at which point the flow transitioned from laminar to turbulent? I know we can do u+ vs y+ for a flat plat boundary layer profile. But for an airfoil/turbine cascade that is curved...what is the method? My geometry is attached below

The shear in laminar boundary layer is smaller while that in turbulent one is larger. How about plotting a skin friction coeff along the curved wall? A big jump in it should indicate the transition.
OJ 
there is no laminar flow in fact and all turbulent models can solve so called laminar flow, so u should consider all field as turbulent specially in geos like turbines!

You can plot intermittency, turbulent kinetic energy, turbulence intensity and integral parameters.
I don't know how you can use skin friction to infer transition, may it is a good indicator of separation but have no idea about transition. I'd interested to find out that how we can use skin friction... 
The approach I mentioned is, of course, just one of the many popular ways of judging the transition. When there is enough motivation for transition, the TollmienSchalichting (TS) waves are developed in the flow which typically are 2D. The waves produce disturbances and slowly they grow into 3D structures giving rise to local vortices etc creating a high shear region.
Skin friction coefficient is of course a measure of this shear. Hence its plot on streamwise direction provides a point where the skinfriction shoots up, an indication of transition. OJ Ref: Castelli, M. Raciti, G. Grandi, and E. Benini. "Numerical Analysis of Laminar to Turbulent Transition on the DU91W2250 airfoil." Hanjalic, K., Y. Nagano, and S. Jakirlic. "The application of laminar kinetic energy to laminarturbulent transition prediction." Johansen, Jeppe, Jens N. Soacute, and rensen. "Prediction of laminar/turbulent transition in airfoil flows." Journal of aircraft 36.4 (1999): 731734. 
can you send these papers to turboenginner@gmail.com

Sent, cheers
OJ 
Oj
Thanks a lot. 
All times are GMT 4. The time now is 22:28. 