Solver error

[sonali.mhetreZKVTC]

I am trying to run CFD analysis on multiphase condition. As I have added boundary condition - quality, the error started occurring. I have followed steps given on CFD support and learning for two-phase mixture. I have attached print screen for reference.

[karol.suchon]

Hello,

that is the software regression, the error appears during the boiling initialization.
In that case, instal version 2019.2.

Best regards, 
Karol

[sonali.mhetreZKVTC]

Hi,
Thanks for your solution. But the current version installed on my laptop is CFD 2021.
I think this is next version of 2019.2. So, there should not be any glitch or error in software above 2019.2 versions.
If I am wrong, please correct me.
Thanks & Regards,
Sonali M. Mhetre

[karol.suchon]

Hello, 

You are right, but sometimes between the version some errors reappear from the previous one. 
that's why I called it software regression.

Regards,
Karol

[sonali.mhetreZKVTC]

Hi,
I ran the more iterations but now error is not appearing during the boiling initialization, it is appearing after 99 iterations. kindly help me to find the solution.
Thanks & regards,
Sonali M. Mhetre

[karol.suchon]

Hello Sonali.

probably now we have the standard solver error connected with the divergence.

Please let me know if you ran the scenario for 100 iterations, in that situation the problem could be connected with saving the data or computing some parameter at the end of the simulation.

To solve the issue check if you have all necessary boundary conditions parameters.

If that does not help, please attach the simulation.

Best regards,

Karol

[sonali.mhetreZKVTC]

Hi Karol,

Thanks for your suggestion. I have checked boundary condition as per the guide. But still the error is appearing at 99th iteration. I have attached zip file herewith. Please take a look and let me know, why the error is appearing.

Thanks & Regards,

Sonali M. Mhetre

[mar.wen]

The same happened with my simulation before. I am using CFD 2021 also so I am following the progress of this forum post. At that time, I thought the problem was my computer specs or set-up settings but looking at your model and set-up, I think now that it was not the case. 

[mar.wen]

By the way, I tried to run your file into two phases. Flow only and then with temperature. I successfully run the flow-only phase but same error when the heat transfer was re-introduced.

[sonali.mhetreZKVTC]

Yes, there is the problem. The problem is with heat transfer not with flow. Now, I'll try same model with different saturated fluid. And will let you know.
Thanks & regards,
Sonali M. Mhetre

[karol.suchon]

Hello guys,
I checked the model and that looks like the error appears on the last iteration, even if I ran the simulation for the one iteration. I was able to run the simulation without the solid elements. I know that does not make any sense for computing that, but I just want to check. Also during the simulation, the temperature is somehow fixed. So probably software is not able to exchange the temperature field to calculate the phase change. I will try to compute the same simulation in CFD 2019 and will let you know if that helps.

Best regards, 

Karol

So I think 

[karol.suchon]

Guys, 
I ran the simulation in CFD 2019, and get the results without any problem. Of course, I will focus more on the mesh etc, but the results are generated in the proper way.

I think that somehow you are avoiding the initialization problem, but the real problem with the phase change still exists.
Best regards,

Karol

[mar.wen]

Is it then really related to the CFD version?

[sonali.mhetreZKVTC]

Hi Karol,

Thanks for simulation. So, is the problem with software version? And for phase change, am I applying wrong boundary conditions or material? I did not created material, I just applied from default source.
In the image, which you attached, the fluid in inner pipe is showing the temperature difference from 35 deg C to around 65 deg C. But there is no any temperature difference at outer pipe. It is in same colour (red). As per my opinion, there should be temperature drop irrespective of mass flow rate.
What is your opinion? please let me know.

Thanks & Regards,
Sonali M. Mhetre

[karol.suchon]

Guys, I recreated the scenario in version 2019.2 so I think that is related to the software version.

There was a little difference in the pipe, but probably the difference in density, velocity etc generates that the change is just much lesser. 
best regards, 

Karol

[sonali.mhetreZKVTC]

Hi Karol,

Thanks for your reply. So what do you think, how can we solve this issue?

Regards,
Sonali M. Mhetre

[karol.suchon · Accepted solution]

Hi Sonali, 
the solution is simple, install the previous version which allows to solve phase change without problems and recreate the scenario. There are a few possible problems with the simulation connected with the mesh etc, but first, we need to build a simulation that produces the results.
Best Regards,
Karol