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-   -   flow patterns (http://www.cfd-online.com/Forums/fluent/29210-flow-patterns.html)

gorman January 3, 2002 06:07

flow patterns
 
I think fluent will never able to show flow patterns in pipes.Please tell me any scheme that could be use to this purpose? Thank you

John January 3, 2002 06:18

Re: flow patterns
 
Do you mean secondary flow in the cross-section of the pipe?

gorman January 3, 2002 10:30

Re: flow patterns
 
hi,

i am trying to stimulate a segregated flow and/or observe flow patterns such as wavy flow, bubbly flow,slug flow etc. As i am dealing with 2 phases (CO2 and oil), i wish to observe the flow patterns of both phases in a vertical pipe and a horizontal one.

Please advise,Thank you.

John January 4, 2002 06:55

Re: flow patterns
 
In this case, only Fluent guys can answer it.

gorman January 4, 2002 12:08

Re: flow patterns
 
Thanks,

However, please advise me of what in your mind? I wish to discuss more around the focus. How about the secondary flow in the cross sectional area that you mentioned?

John January 5, 2002 16:43

Re: flow patterns
 
You have to use a non-isotropic turbulence-model.

gorman January 6, 2002 23:17

Re: flow patterns
 
how do I set my model to a non-isotropic turbulence model? I am doing a vertical pipe. Thank you.

Lanre January 9, 2002 13:22

Re: flow patterns
 
So you are trying to model vertical two-phase gas-liquid flow. The multiphase models in FLUENT 6 are capable of modelling the various flow regimes you are interested in. The many multiphase models are developed for certain types of flow regimes. Hence, you may not be able to model flow regime transitions from surface-dominated to inertial-dominated flow regimes, e.g., dispersed to plug. You can model transitions, say from plug to slug in a vertical flow or stratified to wavy to slug and possibly even annular in a horizontal flow.

Take a look at the training notes on multiphase flow to guide your selection of model and fit to range of flow regimes at http://www.fluentusers.com/fluent5/training/9amulti.pdf

gorman January 10, 2002 03:36

Re: flow patterns
 
Thanks alot, u mentioned FLUENT 6, how about FLUENT 5.0? is it possible also?

Lanre January 10, 2002 10:50

Re: flow patterns
 
Some of the flow regimes you describe would be more accurately modelled using the Eulerian multiphase models that are available in FLUENT 4.5 and FLUENT 6 but not FLUENT 5.x

gorman January 10, 2002 12:16

Re: flow patterns
 
To model vertical two-phase gas-liquid flow for CO2 and fuel-oil-liquid, Do you think using k-epsilon viscousity is proper? What assumption has to be made in using laminar flow? I am not sure how FLUENT would define both cases. Thank you for your advise.

Lanre January 15, 2002 15:33

Re: flow patterns
 
I don't think the k-e turbulence model is "proper" in the absolute sense of the word for either single or multiphase flow problems. The deficiencies are well known and are published in the literature. For multiphase flow calcs in FLUENT, the k-e model can be used to model the turbulence in the primary phase only or in both the primary and secondary phases independently (four equations solved for two phases). There are documented rules on which of the two approaches is most valid for specific applications. If the flow is laminar, you don't have to use a turbulence model at all.


gorman January 16, 2002 18:17

Re: flow patterns
 
Hi,

How can I determine whether it is gonna be a laminar flow? I am modeling gas lift system, pumping high velocity gas into well shoe and pump up the crude oil to the well head. Can it considered a laminar flow?

I have also determined to choose ASM model as gas and oil will form a "uniform' body and transport upwards.Do you think my set up is proper? Thank you.


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