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candy April 8, 2003 23:56

I 'd like to set 3 particle injections(e.g,30particles for each injections) for different diameter of 20um,1um,0.01um and compare the deposition velocity. i am using the unsteady tracking, the problem is when i starting the iteration, Fluent mix the 3 injections together,that is ,it will show on the console windows: number tracked=90,trapped=15,escaped 75,sth like this,so i can't get the trapped number of particles for each diameter.can you help me ?thanks

Alex Munoz April 9, 2003 01:10

Re: dpm

I was thinking in your case!

Why do you want to run the three diameter in only one iteration??

I think you can run each diameter separately in order to measure the variable that you request, after all the particle tracking is individual for each particle and it is not affected by other particles!

In addtion I think that 3 point of injection are to low! perhap more point per area could be more representative for your case than 30 particles launched from one point!

Give your comment back I am interested in your case!


candy April 9, 2003 01:57

Re: dpm
thanks for your responsing!

i mean if i can submit 3 injections(just the particle diameter is different,the other parameters are the same)in one time steps and get the results seperately.but now i can only put one injection at one time. for example, i need the results during 20 time steps, one time step costs 1 hour, then for one injection i need 20 hours, if i put the injection one by one, then i have to spend n*20 hours!so i wonder if i can put all the injections together, and then the time need is only 20 hours.

hope i explain it clealy,thanks!

Alex Munoz April 9, 2003 15:14

Re: dpm
HI Candy

Yes i can help you!


Made Three files with the following format and information data

((x,y,z,v,v,w,d,T,mass-flow)injectionID:particle ID) where x,y,z are the cordinates u,v,w, are the absolute velocity of the particles d diameter m T temperature Kelvin Mass-flow Kg/s Injection ID: particle ID=Injectioni:j where i the number of point for injection (in your case 0 to 2)and j the number of particle per injection point (in your case 0 to 29)

Then read that files in your injection window (below single, group, surface you will see file) Then at the bottom of the injection window you will se a box with the name file.. Click on the file.. box and select the file (name the file candy0.inj, candy1.inj and candy2.inj) Then, run the particle tracking for you steady case Make sure that you are getting reasonable results Then, write a UDF dpm Outlet to write a file with the variable that you wish Then, open report>discrete phase>sample> select you surface, injection and output file compute, plot the histogram report>discrete phase>histogram make sure that your statistical moments for the variables of concern does not change after incresing the number of particles Then, run the unsteady case with all you injections Import the output.dpm file to Excel Then, you can see the variable of concern for each injection ID:particleID Finally you can play with your results as you want!

Have fun! If i miss something think smart!



Alex Munoz April 10, 2003 19:14

Re: dpm
Hi candy

Now, I need you help

I have not run unsteady particle tracking! could you please explain me how you do it

Thank you


candy April 10, 2003 23:10

Re: dpm DISCRETE PAHSE MODEL panel, select Unsteady tracking. 2.go to Injections-set injection property-creat,if you select a surface as injection, then on the below of the panel, there will exist "point properties" for unsteady tracking ,it will appear the item"start time " and "stop time", particle will be released at every time step during the period of time you defined. after the period of time you set, particle will still be tracked until all the particle are trapped or escaped or .... 3.note that unsteady tracking is caculated together with the fluid iteration,that is,open "iterate"panel, and "iterating", after each time step iteration, the particle will be released and caculated.

hope the above is useful, good luck!

hedonist April 10, 2003 23:23

Re: dpm
unsteady particle tracking is only active when you select the unsteady option in the solver.

Alex Munoz April 11, 2003 11:57

Re: dpm
hello Candy and Hedonist

Thank you for your information!


Alex MUnoz

Alex Munoz April 11, 2003 12:02

Re: dpm
Hi candy

I forget to ask you one detail.

is your DPM couple with the continuous fluid? becuase my case is not couple with the continuous flow, and I wonder if I need to iteterate the flow.

Thank you for answer me these questions!

Best regards

Alex Munoz

candy April 11, 2003 21:33

Re: dpm
my case is also not couple too, but it is also needed to iterate the flow, otherwise how can you do the unsteady tracking since the case and data file only record the flow in a definite time?

Alex Munoz April 12, 2003 14:02

Re: dpm
Hi Candy

Thanks alot for your reply, I thought about it!

Just I want to be sure

Thank you

Alex Munoz

Alex Munoz April 12, 2003 14:21

Re: dpm
Hi candy

I want to ask you another question!

Perhap, you wonder Why I don't run Fluent and I check for myself, Currently, we are making modification and I cannot run an iteration for more than 5 minutes using the GUI, if I run iteration for more than 5 minutes I have to do it under batch mode. I don't know if you have working under this mode but I have to be 100% sure what I am doing.

The question is the following

I have to report particle tracking under Report>DPM>Sample and I have to speficy the Start time and Stop time. Fluent documentation say the that

"For unsteady particle tracking, clicking on the Start button will open the files and write the file header sections. If the solution is advanced in time by computing some time steps, the particle trajectories will be updated and the particle states will be written to the files as they cross the selected planes or boundaries. Clicking on the Stop button will close the files and end the sampling"

I am very confuse with this information perhaps you can help to understand this issue.

Thank you in advance!

Alex Munoz

barzin August 6, 2012 12:06

Dear Alex

It has been a long time that you have posted the last statement. How ever I was wondering if you still use this forum since I have the same problem with sampling. Just wanted to know hoe to do this ! please help me!

sajeesh May 5, 2013 02:10


How i can calculate the number of particle in one injection..when i am doing unsteady particle tracking i am not getting any result i the CFD post processor(any plot)..I dont know what is the problem...How can i set the time period..
In my case.
The fluid is moving with 0.3 m/sec in a 1000 micro meter channel..I need exactly one particle to trace the flow.of size 50 micrometer.density of particle is 998 kg/m3. the continous phase is oil. How i keep the time step for unsteady particle tracking.and the number of time step..and the time of injection

Please help me

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