[aja1345]

Hi,

I am simulating turbine. First, I ran with 448505 cells and results a.

lls, there is the following error, Why?

turbulence model is K-e scalable. Analysis type is steady.






Thanks for your help.

[-Maxim-]

This is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

[aja1345]

Thanks.

According the following text, What is the exact meaning of "time step"? Time step is about unsteady solution. right? or is time scale??

• Does the model require small time steps to start? Some simulations require small time steps to start, but once going the time step can be increased.

[-Maxim-]

yes, in a steady-state simulation it's timescale. Are you using auto timescale? Try different factors. Like 0.1, 1, 10, 100.
I've never used k-e scalable. So I don't know if any restrictions apply with this model. Maybe worth to check. Why aren't you using SST? It's the standard model for CFX and F. Menter, inventor of this model, works with Ansys - so that model should work the best

[aja1345]

Originally Posted by -Maxim-

yes, in a steady-state simulation it's timescale. Are you using auto timescale? Try different factors. Like 0.1, 1, 10, 100.
I've never used k-e scalable. So I don't know if any restrictions apply with this model. Maybe worth to check. Why aren't you using SST? It's the standard model for CFX and F. Menter, inventor of this model, works with Ansys - so that model should work the best

Thanks.

According to your statement, I used auto timescale and I change value of factor and also i used physical timescale, but there is the Error!!! I think that mesh quality is good. But about initial condition, I set options according ANSYS CFX 15.0 Documentation. I have not enough other information about intial condition. i set this case as follows:


For example, I had changed value of physical timescale to 0.1, but there is error in outer loop 12 as follows:

About SSt model, I performed with sst, but again there is previous problem!


Thanks for your guidance.

Best.

Aja

[ghorrocks]

It is not an error, it is a warning. See this FAQ: http://www.cfd-online.com/Wiki/Ansys...f_an_OUTLET.22

Also - refining the mesh makes convergence harder, not easier. You should expect more problems getting convergence as you refine the mesh.

[aja1345]

Originally Posted by ghorrocks

It is not an error, it is a warning. See this FAQ: http://www.cfd-online.com/Wiki/Ansys...f_an_OUTLET.22

Also - refining the mesh makes convergence harder, not easier. You should expect more problems getting convergence as you refine the mesh.

Thanks.

But when this massage appears, solution diverges!!!

I read FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

I have one question about above link:

Is opening type boundary condition can be placed from the beginning in outlet?

In CFX documentation and the tutorial examples,it is not explained about this warning messages completely!!

How do I solve this case??

I am grateful that guide me more.

Thanks.

[ghorrocks]

The best approach when you get the "a wall has been placed..." warning is to move the outlet further downstream so that the recirculation does not hit it and the flow is all in the forwards direction. If this is not possible then replace it with an opening. And in some cases you can just ignore it and continue anyway.

But if you are having stability issues then you should try to move the outlet further downstream to avoid the problem. Also have a look at mesh quality in general. Any improvements in mesh quality will have a major effect on convergence.