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-   -   Multiphase flow and MRF (http://www.cfd-online.com/Forums/cfx/18582-multiphase-flow-mrf.html)

Yenni Chiu July 17, 2001 02:29

Multiphase flow and MRF
 
Hi,

I am trying to extend the application example 5 in CFX4.4, a rushton impeller with moving frames of reference, to a multi-phase fluid flow of gas and liquid. Based on the command file from the example, I added another phase and commands for MULTIPHASE PARAMETERS as well as the following lines under ROTATING COORDINATES PARAMETERS, i.e.
:>ROTATING COORDINATES

PATCH NAME 'USER3D-ROTOR'

OMEGA

POSITION VECTOR ON ROTATING AXIS 0.0 0.0 0.0

ROTATING REFERENCE DENSITY the gas density

The field was initialised to half filled with liquid at the bottom and no inflow/outflow. The computation stopped after a few iterations with error saying floating overflow.

Can anyone point out the possible error I made or commands I missed out? Thanks heaps in advance.

Herve July 17, 2001 05:44

Re: Multiphase flow and MRF
 
Have you tried running the application as it is in the manual? Have you used the geometry from the example, in which case you will have noticed that you need to mend the geo file for the inside block to go between 1 and 27 instead of 2 and 27?

Yenni Chiu July 19, 2001 04:04

Re: Multiphase flow and MRF
 
Thanks for the response. Yes, I ran the application example as it is in the manual and also corrected the geo file. I now add false timesteps to 1.0E-4, the calculation goes but results are very unsatisfactory. The command set up is very basic for a multi-phase model. Is it too simplified to cause the difficulties? Yen

Herve July 19, 2001 11:06

Re: Multiphase flow and MRF
 
Multiphase is generally difficult to set up, and one could question the way you have set your model up. It would be good if you could post your command and fotran files to see in more details what you have done.


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