|
[Sponsors] |
recurring issues with mass/species conservation in fluent |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
January 5, 2016, 05:42 |
recurring issues with mass/species conservation in fluent
|
#1 |
Senior Member
Cees Haringa
Join Date: May 2013
Location: Delft
Posts: 607
Rep Power: 0 |
Dear all,
There are 2 major recurring issues I am encountering in ANSYS FLUENT (i've worked with 14.5, 15 and 16), and I would like to know if more of you have experienced these issues, and perhaps have workarounds. Problem 1 is the conservation of mass in multiphase simulations with a pressure-outlet boundary condition. I am modeling a tank/bubble column, with mass-flow or velocity inlet, and pressure outlet. There is a freeboard region filled with gas only (20% of the domain height), and the pressure outlet has a 100% gas backflow specified. There is no feed of the continuous liquid phase. Still, the mass of liquid is not conserved; I've seen it both going up and down. This happens both in steady state and transient simulations. the imbalance happens at the outlet, but I cannot see why - especially I cannot understand why the water mass sometimes increases. In either case, the simulation does not converge, or converges with a large part of the water gone. Problem 2 has to do with species tracking. I switched to a degassing B.C. (removing the freeboard region, so the tank is filled with gas-liquid mixture to the top), so that problem 1 is gone. However, when I enable the species equation, there is a continuous increase in the mass fraction of the non-bulk species. So, I feed gas with an oxygen content of 20%, but at the outlet boundary, gas with a 100% oxygen content flows back. I suspect this has to do with the backflow condition at the boundary - however, one cannot specify that for the degassing b.c. Do these problems sound familiar? Any suggestions or workarounds? Any comments would be of enormous help, since I am pretty stuck at this moment - and with the amount of work already done in FLUENT, switching to CFX would be a pretty unfortunate last resort. |
|
January 11, 2016, 08:42 |
|
#2 |
Senior Member
Cees Haringa
Join Date: May 2013
Location: Delft
Posts: 607
Rep Power: 0 |
So, I guess nobody ran in to these issues (or has a workaround?)
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
How to start Fluent with Matlab?? | Jay Hu | FLUENT | 8 | November 9, 2022 06:30 |
Linux Fluent HPC parallel system check failed | saad3000 | FLUENT | 1 | January 8, 2021 03:34 |
What the differences flow equation of Fluent 6.3 and Fluent 12.1 | opehterinar81 | FLUENT | 0 | August 19, 2011 11:55 |
Fluent 6.3 32bit vs Fluent 12.0 64bit | ibex7 | FLUENT | 7 | April 18, 2011 02:44 |
Master node in parallel computing only distirubtion | syadgar | FLUENT | 1 | September 8, 2009 16:41 |