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Old   February 15, 2010, 14:56
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karine
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Hi my friend
thanks for ure comment
I am sorry, but i dont know how to model such cases with phase change...
All what i can tell u is:
1-ure problem is so complex, and to choose a suitable model, u must know a priori ure flow regime. One of the complex things is that the interface velocity will be different from the velocity of the phases on the interface......This is due to mass transfer mechanims
2-Are u sure that ure flow is 2D??????????????? Remember that while condensation is occuring, the liquid phase will occupies the bottom of ure pipe so i dont see how ure problem is 2D....
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Old   April 6, 2010, 16:53
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Hi All,
Great thread. I am also using VOF solver for two-phase flow in a pipe. My problem is that I am not getting convergence with continuity. My pipe is 50 mm dia and 4 m long. I am trying to simulate stratified flow and wavy flow (by increasing the velocity of air). I have a split inlet (1:1) and single outlet. I got a good volume fraction contour for stratified flow, but convergence is still a prob. I had 0.25 m/s water inlet and 1 m/s air inlet.
Can you suggest something. Should I tweak the pressure correction values or anything?

Thanks,
Pranab
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Old   April 8, 2010, 23:00
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I have a small query regarding my simulation.
I am using the Taitel-Dukler flow maps to get information on the flow regimes. In the theory the Reynold's number that has been used to predict the turbulent flow (as usual) at more than 2000 approx. But Re is calculated using the dia of the pipe. In my case, I have a split inlet in 1:1 ratio for gas and liquid. So should I calculate Re using the Hydraulic Dia or regular dia of the pipe?
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Old   April 27, 2010, 19:23
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Hi
it have been a long time that i have not been connected and it is just now that i saw ure message
Why do u need to know if ure flow is turbulent???? flow with a free interface are less stable that confined flows, so u will get turbulent flow for a Re less then 2000.
About Re: Re=rho.Vel.length/visc
The best is that u use vel=superficial velocity and legth=the pipe diameter
But as i told u, the limit to turbulent will be less then 2300 and it will depends very much at the inlet (experimental) conditions
About the taitel and Duckler map, it will give u an idea about ure flow regime but remember that their map have been done for a 2.5 cm diameter pipe , and it have been done using a model and not experiments
An interseting map is maybe Mandhane's map, wich Taitel and Duckler used to compare with
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Old   July 17, 2011, 15:39
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Hi,
I am trying to perform multiphase simualtions but with solid liquid slurry mixture in horizontal pipes. Could you forward me the paper ""CFD modeling of flow profiles and interfacial phenomena in two-phase flow in pipes" or if you have any other papers which could help me in simulation solid liquid slurry. I am using FLuent. Thanks for your help.
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Old   July 17, 2011, 15:40
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sry for the post, i posted it in wrong post..
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Old   July 17, 2011, 15:51
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Hi cfduser,
Do you have any experience in turbulent solid liquid flows in pipes. I am trying to perform simulation in unsteady state and calculating pressure drops with increasing sand concentration. I am having some issues with the simulation as in with increasing sand concentration the pressure drop doesnt increase. I am using velocity inlet as my inlet condition and pressure outlet as my outlet. The pressure outlet is at atmospheric conditions and velocity inlet magnitude is 725 ft/ min. the lenthg of the pipe is 6.35 m and i have discretized the pipe into cell length of 0.027 ft or 0.0082 metres. The time step size should be ideally (0.027ft/12ft/s)=0.0025 sec. I have kept time step arnd 0.004 sec. Am I correct, in the steps I am doing. If you can share your experience in laminar flow simulation it would be of great help. Thanks again.
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Old   August 8, 2011, 05:42
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Hi all! i have followed this discussion for some months now, since i'm using vof too.
I'm trying to simulate an open channel flow both in 2 and 3d. (basically i use 2d to have faster results and see if it works or not ^_^ ) i've done plenty of simulation and yet i'm not able to get some good result: there's always a point where the fluxes accellerate near the interface water-air at the outlet... i've been using k-epsilon realizable model, (wanted to try your RMS but i've not understood where i find it, is it the reynold stress model? )
i was wondering if anyone had already done a simulation like mine and could post how to set it up or the report->summary of his simulation. I'm trying to make my simulations work for some months now and at my university none ever did an open channel so i cant ask for help here.
thank you very much for your time!

and by the way a special thank to thecfduser since his answer to others really helped me!!
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