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-   -   Angular Velocity of the particle (http://www.cfd-online.com/Forums/fluent/120028-angular-velocity-particle.html)

vagaikwa June 28, 2013 14:28

Angular Velocity of the particle
 
Hello,
I am using DPM model and trying to simulate flow of few particles through fluid. How do I know if my particles are having any angular velocity? And if not how can i impart angular velocity? I have enabled Saffman Lift but it is not generating any lift on my particles.

Thanks.
Varad.

sadjad.s June 29, 2013 05:52

Answer
 
Hi mate,
I am rather sure DPM can not see angular motion of particles.
You see, particles should be too small, hence angular velocity would be negligible.
About Saffman force, if particle and flow velocities become equal, which will be after a while, Saffman force is zero.

vagaikwa June 29, 2013 09:34

Thanks for your reply.
Yes that is what is exactly happening. The velocities of particle and fluid becomes equal after a while. So which model should I adopt if I want to simulate particulate flow and see the translational and angular velocity effects and lift on the particles too.

sadjad.s June 29, 2013 09:40

Answer
 
To see that you need to model 6DoF (Dynamic mesh). But problem is that it fails when particles strike to each other.

vagaikwa June 29, 2013 09:46

I thought of using Dynamic mesh. But the issue is my particle diameter size to tube diameter size is 0.04. Also I have to simulate flow 8 particles and then go upto 100-200 particles.

sadjad.s June 29, 2013 09:52

Answer
 
This is DPM limitation and you may have to neglect angular velocity.
Other problem is your rather big particles sizes. I mean particles with 4% size of characteristic length are rather big for Discrete Phase and can fully change flow pattern. You may switch to Eulerian method.

vagaikwa June 29, 2013 09:52

Sadjad,
Do u think I should still go for dynamic mesh?

vagaikwa June 29, 2013 09:56

Oh the size is big? I thought it is small. Because the references I am using they have the ratio of particle to tube diameter size higher than what I am trying to do. Thanks for your help brother.

ldm273507 December 26, 2013 03:09

Hi,friend. I want to simualte the movement of water droplet. If you konw how to control the velocity of the water droplet using the DPM model? I write an UDF about this, but it's incorrect, could you give me some suggestion?
#include "udf.h"
#include "dpm.h"
DEFINE_ADJUST(my_adjust,d)
{
Tracked_Particle *tp;
cell_t c=P_CELL(tp);
Thread *t=P_CELL_THREAD(tp);
Particle *p;
if(P_POS(p)[2]<14.8&&P_POS(p)[2]>=13.4)
begin_particle_cell_loop(p,c,t)
{
P_VEL(p)[2] = -0.2;
}
end_particle_cell_loop(p,c,t)
}
"Uninitialized varible ’tp' used" and "Uninitialized varible ’p' used" appears when I compile the UDF.
Thank you.


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