Exporting multiple flow data from particle tracks
 

Hi,
I am simulating (FLUENT 12.0) a turbulent flow with discrete particles (including the Discrete Random Walk Model). By using GraphicsAndAnimations -> ParticleTracks it is possible to export a xy-plot of for example turbulent kinetic energy over residence time for each particle. But I want many flow properties (turbulent kinetic energy, dissipation, ...) over the particle tracks. If I click "write" several times FLUENT will perform a new particle tracking calculations and thus the two files are not comparable. I have also tried with the Step-by-stepReport in the same menu but that will only give me particle-variables, not flow variables. Export->ExportParticleHistoryData, seem to do the same as ParticleTracks; re-calculates the tracks for each time I write to file.

Does anybody have an idea?
I would greatly appreciate any ideas.

Found a way of doing it
 

Ok, I found a way myself, but it is not pretty: Extracted the whole field and step-by-step report for particles separately. Then exernally (MATLAB) I go through each track and interpolates the flow variables.
This will work for my but I am still interested if someone knows how to do it inside FLUENT.

Kind Regards
Andreas Håkansson

Hi,
you can also do that by implementation of a simple UDf. e.g. with a macro that execute at every particle step and write desired flow properties of cells that contain the particles.

Thanks for your reply Amir!
I have been think on using a UDF but I was not sure how. My idea was back then to use DEFINE_DPM_OUTPUT. However it seems tricky to access flow-variables. I would need to know in what cell each particle is a each time. I never really figured out how to do this.
My other suggestion was to just use the DEFINE_ON_DEMAND but i run into the same problem of finding the cells where particles are. Also in DEFINE_ON_DEMAND I never figured out how to obtain the particles.
Any suggestions?

it's not difficult to find cell and cell-thread index that contain a particle. FLUENT has two functions for that:
P_CELL(p),P_CELL_THREAD(p)
but you should use them in compiled UDFs.

Hi, Andreas Håkansson,
Now that you use DRW to take into account for the turbulent dissipation, it is meaningless to present properties one time for only one particle.

Amir: Thanks, I didn't know about these functions. That is probably the solution.

xrs333: Thanks for your reply. I agree with you, I simulate at least 100 particles with the DRW (or until I reach convergence in my external simulation) but I want all of the flow variables for the same particle tracks. That was my problem. But I think I can solve this with Amirs anser now.