# Problems with two-phase simulation

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 June 23, 2014, 09:06 Problems with two-phase simulation #1 New Member   Mauricio Join Date: Jan 2013 Location: Vitoria - ES - Brasil Posts: 5 Rep Power: 6 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

 June 23, 2014, 19:30 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,884 Rep Power: 107 What is the problem you are having? Please post some images of the result, your mesh and the CCL for your setup.

June 24, 2014, 16:33
#3
New Member

Mauricio
Join Date: Jan 2013
Location: Vitoria - ES - Brasil
Posts: 5
Rep Power: 6
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
 Vaezi_Malha.jpg (36.5 KB, 16 views) Vaezi_Geometria.jpg (15.3 KB, 16 views) Vaezi_Vol_Frac.jpg (29.2 KB, 18 views)
Attached Files
 CCL_Vaezi.txt (9.3 KB, 6 views) Boundary_Flow_Sumary_Vaezi.txt (6.6 KB, 6 views)

 June 24, 2014, 19:14 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,884 Rep Power: 107 Do you simply need to run it for a longer physical time?

 June 25, 2014, 07:42 #5 New Member   Mauricio Join Date: Jan 2013 Location: Vitoria - ES - Brasil Posts: 5 Rep Power: 6 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,

 June 25, 2014, 07:56 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,884 Rep Power: 107 Run it for more iterations, possibly with a tighter convergence criterion.

 June 25, 2014, 08:44 #7 New Member   Mauricio Join Date: Jan 2013 Location: Vitoria - ES - Brasil Posts: 5 Rep Power: 6 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

 June 29, 2014, 23:24 #8 Member   Thiagu Join Date: Oct 2012 Location: India Posts: 59 Rep Power: 7 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

 June 30, 2014, 07:44 #9 New Member   Mauricio Join Date: Jan 2013 Location: Vitoria - ES - Brasil Posts: 5 Rep Power: 6 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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