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Old   June 23, 2014, 09:06
Default Problems with two-phase simulation
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Mauricio
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Hi,
I'm trying to simulate a water-particle two-phase flow in a helical geometry, but the particles accumulate in the domain.
Adopted water as a continuous fluid and kaolinite (density of 2560kg/m3, with a mean diameter of 2 microns) as dispersed solid.
I configured as boundary conditions:
Inlet: bulk mass flow with volume fraction of 0.9 for fluid and 0.1 for particles;
outlet: bulk mass flow;
Wall: no slip for fluid and slip free for particles.
As the solid phase has a density greater than the liquid phase, I had not considered lift and virtual mass forces.
As stated, all particles stay into the domain, though it reaches the convergence of both the flow and the volume fractions.
thank you very much
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Old   June 23, 2014, 19:30
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Glenn Horrocks
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What is the problem you are having? Please post some images of the result, your mesh and the CCL for your setup.
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Old   June 24, 2014, 16:33
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I'm having problems with the volume fraction solution of dispersed solid.
The solid phase does not exits of the domain.

I describe below the sent files:

The figure named "Vaezi_Malha.png" is the mesh of inlet section. The mesh was constructed using the sweep method.
The figure named "Vaezi_Geometria.png" is the problem's geometry.
The figure named "Vaezi_Vol_frac.png" is the contour plots of solid phase volume fraction on the sections (from bottom to top) inlet, 360 (turn one), 720 (turn two), 1080 (turn three), and outlet.

tanks
Attached Images
File Type: jpg Vaezi_Malha.jpg (36.5 KB, 12 views)
File Type: jpg Vaezi_Geometria.jpg (15.3 KB, 12 views)
File Type: jpg Vaezi_Vol_Frac.jpg (29.2 KB, 13 views)
Attached Files
File Type: txt CCL_Vaezi.txt (9.3 KB, 5 views)
File Type: txt Boundary_Flow_Sumary_Vaezi.txt (6.6 KB, 4 views)
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Old   June 24, 2014, 19:14
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Glenn Horrocks
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Do you simply need to run it for a longer physical time?
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Old   June 25, 2014, 07:42
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Dear ghorrocks, tanks for helping me.
I didn't understand your answer.
How to increase the physical time if my simulation is performed assuming steady state?
Best regards,
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Old   June 25, 2014, 07:56
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Run it for more iterations, possibly with a tighter convergence criterion.
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Old   June 25, 2014, 08:44
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Ok,
tanks for your help.
I'll try your tip.
I ran adding lift and virtual mass forces. Although the theoretical basis demonstrate that these forces are important when the dispersed phase is less dense than the continuous phase, the volume fraction results improved. However the flow results worsened.
I hope that by adopting a tighter convergence criterion, I can improve both results.
Later, I notice what happened.
Tanks
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Old   June 29, 2014, 23:24
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Add monitor point for particle volume accumulation and check is it flat or fluctuating. This would indicate the convergence. Also check mass imbalance of particle. Make sure solution is converged. Many times Solver takes more iterations
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Old   June 30, 2014, 07:44
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Thanks for your tips.
With the increased number of iterations and the consideration of lift and virtual mass forces, the volume fractions converged. However, the flow solution lost precision. However, I believe that with small adjustments to my setup I can improve the flow solution.
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