# Turbulent flow simulation in a long pipe

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June 5, 2020, 11:41
Turbulent flow simulation in a long pipe
#1
New Member

Ali
Join Date: Oct 2018
Posts: 8
Rep Power: 6
Hello.
I am working on a simple turbulent flow simulation in a long pipe of length 1m in ANSYS Fluent. The inlet Re is 12000 and inlet velocity is 0.76 m/s. The problem is that the continuity residuals after some iterations remain constant and do not decrease no matter how long you run the iterations. Other residuals decrease and eventually reach the tolerance criteria except the continuity. I have tried changing the viscous model, solution methods, relaxation factors but the continuity residuals never converge .....I am stuck in this loop for a whole month now and don't know what to do....Its only a simple straightforward simulation and i am so much confused ...Please can anyone help me about what am i doing wrong and what solution approach should i use?????
Attached Images
 mesh.jpg (181.5 KB, 16 views) boundary.jpg (57.2 KB, 13 views) modeling.jpg (76.9 KB, 12 views) residuals.PNG (27.5 KB, 16 views) yplus.PNG (12.8 KB, 13 views)

 June 5, 2020, 13:15 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,238 Rep Power: 63 It's probably fine. The continuity residual is scaled differently. If you reset the residuals and keep running the simulation, you'll find that the continuity residual will be stuck at 1. ammarali311 likes this.

 June 5, 2020, 14:35 #3 Senior Member   duri Join Date: May 2010 Posts: 245 Rep Power: 16 Continuity residual is normalized and dropped by two order which may be fine. May be absolute continuity residual is too small from beginning. Don't normalize or scale the residual and check. Other way of confirming the continuity convergence is through mass flux balance. ammarali311 likes this.

 June 5, 2020, 14:39 #4 New Member   Ali Join Date: Oct 2018 Posts: 8 Rep Power: 6 Thankyou for your replies...I will look into your suggestions

 Tags fluent, pipe flow, turbulence modelling