Yplus to high at Boundary Outlet
 

Hello People

I was analysing a heat exchanger ,two tubes one Inside the other, counterflow. The outer Flow is turbulent Re=300'000. Yplus is ok in general just at the outlet it reaches about 600. I tried to replace the boundary with an opening that didnt help. What do you do in such cases? Would you make the tube longer and that way taking it out of the analyzed length? What else could be done?

Thanks in advance

.. In the picture only a fourth of the tube is visible, i worked with symmetries...

could somebody change this into the CFX Forum, i didnt want to have it here, my bad..