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Trajectories outside the physical domain in the particle tracing module

Posted Feb 20, 2012, 3:38 p.m. EST Charged Particle Tracing, Particle Tracing for Fluid Flow Version 4.2a 2 Replies

John R Puentes
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Hey,

I ran a simulation of the behavior of a polymer inside an extrusion tube die by using laminar flow module and the No-Newtonian Carreau Module. Afterwards I added the particle tracing module using the drag force formulation. However, the particle trajectories are located outside the phyical domain. Attached are three pictures with the geometry, the particle trajectories and the poincaire map in order to clarify the problem.

Any ideas why this is happening? Should I used the massless formulation instead?
2 Replies Last Post Feb 24, 2012, 12:46 a.m. EST
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Feb 20, 2012, 11:10 p.m. EST
One reason why this happens is that you do not save the particle tracing results at sufficient time instances. The particles can have legitimate positions at two subsequent solution times, but in-between (where results are linearly interpolated) they will be inaccurate and can easily go out of bounds. The remedy in this case is to save results more frequently. The time step actually taken by the particle tracing solver may also be too large. Check that too.

Nagi Elabbasi
Veryst Engineering
One reason why this happens is that you do not save the particle tracing results at sufficient time instances. The particles can have legitimate positions at two subsequent solution times, but in-between (where results are linearly interpolated) they will be inaccurate and can easily go out of bounds. The remedy in this case is to save results more frequently. The time step actually taken by the particle tracing solver may also be too large. Check that too. Nagi Elabbasi Veryst Engineering
John R Puentes
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Posted: 1 decade ago Feb 24, 2012, 12:46 a.m. EST
Thanks, The problem was the time steps were too large.Now, I have a more accurate solution. However, I used Drag force, but for my physical model I am interested in the mass-less formulation.

I implemented in Set Formulation = Massless, in the Formulation section of the settings under the Particle Tracing node. I don't know if I am missing a boundary condition. In the Newtonian formulation, drag force condition is need. What is the equivalent boundary condition for mass-less formulation?
Thanks, The problem was the time steps were too large.Now, I have a more accurate solution. However, I used Drag force, but for my physical model I am interested in the mass-less formulation. I implemented in Set Formulation = Massless, in the Formulation section of the settings under the Particle Tracing node. I don't know if I am missing a boundary condition. In the Newtonian formulation, drag force condition is need. What is the equivalent boundary condition for mass-less formulation?

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