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plz help urgent_VOF MODEL

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Old   September 11, 2007, 01:42
Default plz help urgent_VOF MODEL
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garima chaudhary
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Dear Sir,

I have a query regarding the use of VOF model in a continuous flow system. I am using VOF model to study the fluid dynamics in the rotor zone of a centrifugal contactor. First, I simulated my cases with VOF model in a cylinder with no flow conditions like given in the fluent tutorials. Now, I have a cylinderical geometry (dimension 2cm is radius and 8 cm ht.) rotating at some swirl velocity. In it the fluid enters i.e. pumped in at the bottom through an annular ring at the bottom at a distance of .6 cm from the centre and then it is thrown out at the top. So for this system first I simulated for a closed system with no flow in and out in the cylinder exposed to atmosphere as given in tutorial and then saved this data. Next, I created a new geometry with same dimension but with the inlet as mass-inlet and outlet as pressure outlet and then build a case for such a geometry with the value of pressure at the outlet as calculated from previous data file with no flow conditions and activated the radial distribution of pressure option at the outlet.Then after building this new case with inlet and outlet, I read the previous data file onto this case with some mass inlet value. but I found that as soon as I started the iteration with this initial achieved parabolic profile(got when simulated for no flow condition) as the starting guess in the continuous flow system, I found that the residuals diverged and the iteration stopped. I TRIED WITH STRATEGY PREVIOUSLY FOR SUCH SIMILAR CASE WHERE IT WORKED BUT NOW ITS NOT WORKING AT ALL.

Also, convergence is also a trouble which I am facing in this model, i TRIED WITH VERY SNMALL TIME STEPS AND TEHN GRADUALLY TRIED TO INCREASE BUT STILL IT IS NOT FOLLOWING CONVERGENCE CRITERIA, SPECIALLY CONTINUITY RESIDUAL REMAINS ALWAYS of order of e-1 or e+00.

Can you please help me out in these issues. I will be highly obliged if u kindly help me out asap. I can send you the case or data files if you need.

Regards Garima
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Old   September 11, 2007, 02:44
Default Re: plz help urgent_VOF MODEL
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wanghong
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refine your grids.
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