Dear All, I solved backward facing step of kim et al geometry.1:3 step hight to whole diameter and 28*step hight whole length and 4*step hight inlet of step using k-eps (wall function) by a collocated simplec code. the reattachment point is around 9.4 .i don't know the reason of this overestimation instead of underpridiction.i prescribed k & eps at inlet but used uniform velocity inlet. at Re=69610.

Looking forward to hearing from you

Hi,

there could be lots of reasons and the task at hand it to evaluate your solver and the implementation of the models, preferably one thing at a time.

I would first suggest doing some of the standard laminar benchmark solutions. Have you tried the laminar backward facing step? How about some of the other standard laminar cases such as the lid-driven cavity, Couette flow and other cases with analytical solutions, etc. You should be able to convice yourself that the code performs as expected ie. if you have implimented a second order scheme that it does perform as such. Also of importance is that you understand and can control the iteration errors, etc.

Once you have determined that your code performs well on the laminar cases then you can move on to simple turbulent cases ie flat plate boundary layers, mixing layer, etc.

Hope this helps.

Bak_Flow

Thanx for your answer.yes i have tried laminar step as well as cavity.the code functions well with laminar.but in turbulence no.i think the problem is out of my mesh. i don't know how i can find a good mesh.mybe by trail and error. anyway i am still trying to find a suitable mesh.maybe a solved problem can be a good hint and help.

[mazdak]

dear Memarzadegan

Do you have any benchmarks that estimate reattachment point behind an obstacle in turbulent channel flow?