CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   Multiphase phase Mixture model (http://www.cfd-online.com/Forums/fluent/37426-multiphase-phase-mixture-model.html)

 Robi July 29, 2005 15:21

Multiphase phase Mixture model

In my multiphase mixture model there are two phases air and water. I have patched the air with the primary phase that is water.Now I get the following message "Reversed flow in 15 faces on pressure-inlet 3. Reversed flow in 18 faces on outflow 4."

What does that mean. How can I make it converge? Any help is highly appreciated.

Robi

 Swarup July 30, 2005 07:00

Re: Multiphase phase Mixture model

Reversed flow is flow in opposite direction to major direction of flow. I assume that pressure inlet 3 correponds to inlet of your domain. it means that you have reversed flow from inlet in 15 faces. outflow 4 is another of your boundaries on the outlet of your domain. there also, flow is coming in from outlet. there is no problem in having reversed flow, except in outflow. reversed flow in "outflow" boundary condition should not be tolerated for a large number of iterations/time steps because logic behind outflow then fails. in such case, you should change outflow to pressure outlet. So, wait for some iterations/time steps to check whether reversed flow stops. otherwise, try changing outflow to pressure outlet (preferrably with 0 gauge pressure). Swarup

 Robi July 30, 2005 13:03

Re: Multiphase phase Mixture model

Thank you Swarup. I will try changing the outflow to pressure outlet boundary condition. But the pressure inlet is not my inlet boundary. It's kind of a boundary where air is present and I am assuming through that wall no mass transfer is taking place. But my assumption could be wrong and since I don't know exactly what is happening at that boundary, may be some air is coming in the computation domain and some air is going out from the domain. That is why I gave pressure inlet boundary condition. Let's see in my next try. Thanks a lot and have a great day. Robi.

 kabilan January 5, 2011 07:42

multiphse flow

i am trying to simulate multiphase flow air and water mixture..
when i solve that problem the error occur as reverse flow.

 sandisk January 23, 2011 20:36

Hi robi,
Do you have any experience with modeling solid liquid slurry with Mixture model ? Please help if you have any experience with such simulations ?

 k.baker January 24, 2011 04:30

this question is too old from 6 years ago she will not answer u

 alilouu February 3, 2011 17:24

hi all
my problem is similar as yours, what are the steps required to solve wth VOf, better than mixture::::using two phases air and benzene, + a free surface between them

 mehdi8619 February 15, 2011 21:38

Mixture & Two-Phase Flow

Hi every one

I'm tiring to model 2-phase flow in a heat pipe with FLUENT. Here it goes :
Viscous: Laminar
Multi-Phase: Mixture model-ON (Slip Velocity- OFF / Implicit Body Force- ON)
Materials: Water vapor and liquid (from the FLUENT database), Cu (from the FLUENT database)
Phases: primary phase (water-liquid) and secondary phase (water-vapor)
Phases: Interaction: Mass: Mechanism: Evaporation-Condensation: Frequency=.1 & Saturation=400 constant (2 same mechanisms, one from phase 1 to 2 and vice versa).
Solution Initialization: Phase 2 - Volume Fraction=0, Pressure=0, Temperature=300 (the whole domain filled with phase 1, water-liquid at T=300)
The geometry and the BCs are also described in the picture. Problem:

AA: water-liquid (Incompressible ideal gas): diverged, AMG solver
BB: water-liquid (ideal gas): phase-1 starts to be transferred to phase-2 while the temperature is not 400 and also the temperature fall to 57 Kelvin and all in all, no sense.

Could any one tell me what the problem might be? (BTW, this the FLUENT I used: Revision: 12.0.16 for the ANSYS Release Version 12.0.1)

http://mehdifamouri.persiangig.com/03.JPG