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convergence problem of three phase flow

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Old   April 23, 2008, 06:02
Default convergence problem of three phase flow
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nick
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hi,I'm blocked by the convergence problem of three phase flow. what i model is that oil,air and water flow through a pipe.

inlet:Cartesian Velocity Components->0,0,3m/s outlet: open,Static Pressure for Entrainment->

->Relative Pressure = 1 [atm] domain: Reference Pressure = 1 [atm] BUOYANCY MODEL: Buoyancy ReferenceDensity=>oilreference air,water---dispersed oil---------continuous ihomogeneous model,no turbulence,

MOMENTUM TRANSFER: Ishii Zuber i take the most Recommended Configurations of Boundary Conditions ,and the simplest fluid model,but it didn't convergence.Where is the problem??

eager to your responses!thank you

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Old   April 23, 2008, 07:52
Default Re: convergence problem of three phase flow
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Andrew
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The most common reason for convergence failure is a poor mesh. Since you are modeling a pipe it should not be hard to get a good hexahedral mesh. Be sure to include small mesh cells near the wall. Even without turbulence, it is important to capture flow patterns near the wall because there is a steep velocity gradient compared to the bulk fluid.

If you are solving an energy equation as well, it is much harder to obtain convergence.
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Old   April 23, 2008, 10:01
Default Re: convergence problem of three phase flow
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nick
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yes,the hexa mesh is good.And what do you mean that"include small mesh cells near the wall"?How can i modify it? And i have simulated water-air two phase flow with turbulence and momentum trasfer convergent.then i do the three phase desire for a convergence result with a simple model. Is there any other problem about my case ,or some advice? thank you
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Old   April 25, 2008, 09:00
Default Re: convergence problem of three phase flow
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nick
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Does the three-phase flow converge so hard??help
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