CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   FLUENT (https://www.cfd-online.com/Forums/fluent/)
-   -   convergence of mixture model (https://www.cfd-online.com/Forums/fluent/34758-convergence-mixture-model.html)

 major October 4, 2004 09:27

convergence of mixture model

My problem is about two-phase flow:liquid and gas.There is a big volume. The liquid inlet is in the upper of the voluem. Two gas inlets are at the bottom. Two outlets are also at the bottom. The structure is symmetry to x and y axle. I select mixture as the multiphase model. The firs step,I didn't select slip velocity and volum fraction of gas. The convergence criterio are 1.0e-05. When converged,I open repor panel. The mass flow of inlet is not equal to that of outlet. Can I consider it has convegerd? And why the mass flow of inlet is not equal to that of outlet? The boundary conditions: inlet:velocity inlet; outlet:outflow Thanks a lot!

 Aly October 5, 2004 13:47

Re: convergence of mixture model

Hi

i am also experiencing same problem with my model as the residuals have gone below 10-7 or so but there is mass imbalance later when i asked somebody here at post following was said by him:

It's not unusual there is some imbalance. Usually it's possible to solve this problem by reducing the value of residual reduction required for convergence. Also try to use a higer order dicretization scheme for convective terms in the solver settings (Solve -> Control -> Solution)...... (ap)

hope its helps

Ally

 major October 5, 2004 21:28

Re: convergence of mixture model

thank you very much! I have reduced the relaxion factors and use the second order dicretization scheme. Mass flow is still imbalence. Mr. Ally, have you solved this problem? And when I change the outlet boundary condition from outflow to pressure outlet, the velocitis of primary phase and secondary phase are different. I don't know which one is correct. Perhaps they are all false for I haven't acquired the converged solutions.

 All times are GMT -4. The time now is 03:41.