Learning Forum

[am21d009]

Dear Sir,

I hope this email finds you well. My name is Bhagaban Jena, and I am a researcher at the Department of Applied Mechanics & Biomedical Engineering, IIT Madras. I am currently working on a simulation project where the air will flow through a gyroid cylindrical tube, using ANSYS Fluent.

While the k-epsilon model converges without issues, the SST k-omega model has not converged despite my efforts over the past six months. I have attached the geometry of the gyroid tube and the residual plot from my simulation for your review.

Here are some details of the steps I have taken so far to resolve the issue:

1.  Verified and refined the mesh quality.
2.  Adjusted various solver parameters, including relaxation factors.
3.  Tested different boundary conditions.
4.  Increased iteration limits and monitored residuals carefully.
5.  Maintain the Y+ also below 1

Despite these attempts, I have not been able to achieve convergence. Given the importance of this simulation to my work, I would deeply appreciate your guidance or any suggestions on how to proceed.
If you need me, I will provide additional details about my setup, such as boundary conditions, initial conditions, and mesh details.

 

Looking forward to your valuable suggestions. Thank you for your time and assistance.

Gyroid tube

 

                                       

                                           Resudual plot of SST k-omega model

 

 

Thanks & Best regards,
Bhagaban Jena, PhD Scholar
Department of Applied Mechanics & Biomedical Engineering
Indian Institute of Technology Madras
Chennai

 

[SRP]

Hi,

The standard k-omega - model which incorporates modifications for low-Reynolds number effects. The low-Reynolds number terms can produce a delayed onset of the turbulent wall boundary layer and constitute therefore a very simple model for laminar-turbulent transition. In general, the use of the low-Reynolds number terms in the k- models is not recommended, and it is advised to use the more sophisticated, and more widely calibrated, models for laminar-turbulent transition instead. So I suggest please have a look at the reynolds number in your case.

[am21d009]

Thank you for your valuable reply, sir. At the inlet, I am varying the Reynolds number from 1350 to 13,500 . Is it appropriate to use the Realizable k-epsilon model with enhanced wall treatment for this case ?

[am21d009]

Thank you for your valuable reply, sir. At the inlet, I am varying the Reynolds number from 1350 to 13,500 . Is it appropriate to use the Realizable k-epsilon model with enhanced wall treatment for this case ?

[SRP]

Hi,

yes, Enhanced Wall Treatment can resolve viscous sublayer flow and heat transfer phenomena if the mesh is fine enough.

[am21d009]

Thank you so much for your valuable feed back sir.