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-   -   Time in particle tracking (http://www.cfd-online.com/Forums/fluent/93468-time-particle-tracking.html)

ali hemmati October 17, 2011 04:59

Time in particle tracking
 
Hello,

I am trying to simulate particle tracking in a steady flow, thus I solved the flow in steady state condition until I have reached stable residuals. I wanted to track the particles using "unsteady particle tracking" in "Discrete Phase Model" panel. But tracking does not occur while iterating the problem in the steady manner. Should I change the flow into unsteady?

Amir October 17, 2011 10:27

Hi,

It doesn't need to use unsteady particle tracking for such case; just use "display-> particle tracks"

Bests,

ali hemmati October 17, 2011 10:47

Hi Amir,

I have tried such method, but it seems that this kind of tracking is not predicted well. My particles have relatively big diameter, so they may change the flow regime. So I thought that treating the problem in an unsteady manner is necessary. Moreover, the results of steady tracking are not consistent--at all!--with a rough estimation which is conducted by Matlab.

Thank you

Amir October 17, 2011 11:01

Quote:

Originally Posted by ali hemmati (Post 328249)
Hi Amir,

I have tried such method, but it seems that this kind of tracking is not predicted well. My particles have relatively big diameter, so they may change the flow regime. So I thought that treating the problem in an unsteady manner is necessary. Moreover, the results of steady tracking are not consistent--at all!--with a rough estimation which is conducted by Matlab.

Thank you

Dear Ali,

Did you enable "Interaction with continuous phase"?
you can use this option in both steady and unsteady tracking; but if you want to use unsteady particle tracking, you have to use unsteady flow solver too.

Bests,

ali hemmati October 17, 2011 13:56

Hi Amir,

I have not enabled "Interaction with continuous phase", because I think that this option enables momentum and heat exchange. My particles do not exchange with flow field.

What is the best attitude to the problem in your opinion?

Amir October 17, 2011 15:46

Hi,

You said that your particle diameters are so big that can change flow field. In common cases, I prefer this procedure:
1) achieve acceptable steady flow field without any particle
2) enable interaction between flow and particle option, which can modify flow field near particles; use this in a steady solver
But in some special cases which presence of particles adds unsteady nature to flow field is a bit more different; e.g. considering vortex shedding in down stream and ....; in such cases, it's better to use unsteady solver for flow field.

Bests,

ali hemmati October 18, 2011 01:30

Hi Amir,

Thank you for your response. I will check this procedure and inform you.
I have selected "surface" as tupe of my injection. Do particles affect each other or not? I want them not to affect each other and behave as they are alone in the flow.

Amir October 18, 2011 03:06

Quote:

Originally Posted by ali hemmati (Post 328330)
Hi Amir,

Thank you for your response. I will check this procedure and inform you.
I have selected "surface" as tupe of my injection. Do particles affect each other or not? I want them not to affect each other and behave as they are alone in the flow.

No, they didn't affect each other in this manner directly, but each particle has its own effect on flow field and these changes of flow field may affect other particles indirectly.

Bests,

ali hemmati October 18, 2011 05:47

Hi Amir,

Thanks, so it seems that I should reduce number of particles which are released from a surface in order not to affect each other as a means of changing the flow field.


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