Learning Forum

[Aerospace24]

Hi guys, I've to analyze flow field around an airfoil (DAE-21, low Reynolds airfoil) under the assumptions of compressible and viscous flow. I've to make different analysis increasing Mach number with the aim to find lambda shock wave on airfoil surface. I've problem with fluent analysis with Mach number > 0.4 (this analysis is ok). In meshing I've added inflation (setting y+=1 using y+ calculator online). When I try to analyze the case M=0.568 and above Mach number, fluent give me following errors: "Divergence detected - temporarily reducing time step.. Stabilizing Coupled to enhance linear solver robustness";  "time step reduced in 1 cells due to excessive temperature change" and so the continuity grows up.
The following one are meshing setup:

 

 

Setup Fluent:

 

Fluent response:

I'm sorry for the for the excessive length of the massage, but I hope I'll get help

 

 

[Rob]

If you've run at a lower speed what trends do you see in the flow as you approach where the model fails? 

[Aerospace24]

At lower speed the continuity is ok and it's about 1e-07 as order of magnitude. Now I managed to run a case with M=0.6 by refining mesh (adjusting maximum layers, and setting bias factor at 55). But if I choose M>0.6 the run fails! My goal is to detect lambda shock wave on the airfoil.

 

[Rob]

So, what changes (in the flow) that could cause a problem?