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Madhukar June 27, 2007 14:06

Particle injections

I want to inject some particles through inlet using Discrete Phase model. Where can i specify the number of particles for the injection.

Any help is highly appreciated.


amir June 27, 2007 15:40

Re: Particle injections
Dear Madhukar

go : Define >injection,then click on create bottom,now you have a new window. set injection type on 'group' ,now you can inter number of particles in 'number of particle stream'. you can determaine first and last piont of particles in point properties. i hope be useful Best Amir

Madhukar June 27, 2007 16:26

Re: Particle injections
Thank u Amir. Is it possible to to define the number of paticles if we select "surface"..instead of "group". Bcos i would like to inject the particles from the inlet.

Thanks again


amir June 27, 2007 16:49

Re: Particle injections
Dear Madhukar yes it is possible, but in that way you have aparticle on every cell center.(for example if you have 200cells in a boundry,you will have 200 particles) but i know you can write a udf to change it, and create desired particle. Best Amir

amir June 28, 2007 05:11

Re: Particle injections
Dear Madhukar i should correct my statement: Particle initial conditions (position, velocity, diameter, temperature, and mass flow rate) can also be read from an external file if none of the injection types listed above can be used to describe your injection distribution. The file has the following form:

(( x y z u v w diameter temperature mass-flow) name )

with all of the parameters in SI units. All the parentheses are required, but the name is optional. so you can write your particle data in a *.txt file and select 'file ' in injectio type drop down list then select your *.txt file. (if you have so many points or your function is complicated , you can create points by a mathematics software(like Matlab) and save a txt type file) Best Rgards Amir

Madhukar June 28, 2007 08:43

Re: Particle injections
Dear Amir,

thank you for a detailed explanation. Actually I am using a UDF(not written by me, but by some external source) to inject the particles(steady particle injections) from a surface(inlet in my case) and collect the information into an output file. Now i would like to do the unsteady particle tracking. I am confused about the time step and no. of timesteps i have to use. My geometry has a length of 5.60 m.

i have found in the user manual that req. time = number of steps * stepsize = avg. distance/avg. particle velocity

here avg. partcile velocity means the velocity of flow or what???

and by using an unsteady particle tracking and when i want to report the sample trajectories to an output file (REPORT-->DiscretePhase-->sample trajectories:) i have selected a surface, and output UDF. Then i clicked the start button. Nothing is written in to the fileWhen I should clcick stop.

I hope u got my problem.

please let me know hat i have to do for the unsteady particle tracking.

Thank you.


Madhukar June 28, 2007 08:45

Re: Particle injections

I can send you the UDF i am using if you would like to see.



amir June 28, 2007 13:14

Re: Particle injections
Dear Madhukar ok ,send foe me, i hope that i can help you. but as i said ,you dont need udf. Bets Amir

margaret mkhosi July 2, 2007 13:31

Re: Particle injections
Hello, I am learning how to use UDF to inject particles from an inlet. Can you send me your UDF file so I can see this is done? Thank you.

Xiana July 5, 2007 10:38

Re: Particle injections

I am simulating particle injections from the inlet too and I would like to try with this UDF. Could you send me it please ( I used particle injections from the surface inlet but they were too many particles. Also I used "skip" by particle tracking panel. A number of "skip = 10" means that Fluent consider only the particles every 10 Cells. Maybe it is useful for you.

Thank you!


margaret July 11, 2007 14:40

Re: Particle injections
Hi, Can you please also send me the udf file you use to inject particles at the inlet? My email address is Thank you

Morteza July 13, 2007 02:55

Re: Particle injections
Dear madhukar you can not specify the number of particles in "Surface" option. in this option for on cell you have one particle therfore if you have 100cell you will have 100 particle.if you want to specify surface and number of particle and diameter of particle and.... , you should write a text file, the format of this text file must be .. ((x y w u v w d T n)) x,y,z position of particle u,v,w velocity of particle d:diameter, T:temp , good luck

akita December 31, 2009 03:54

UDF code

Originally Posted by Madhukar

I can send you the UDF i am using if you would like to see.



Dear Madhukar,

I am doing the research about Particle Injection, my problem is 10,000 particles for 380 faces of inlet. I am trying to manage with injection, could you me your Udf code? I am very appreciate about your ready to help me. My email address is
Thank you very much
Best wishes to you in the new year!!!

cvrgasq224 August 29, 2010 14:01

particle in the pipeline after the deposition trajectory baffle encountered
Members predecessors: I am very anxious! Would like to ask How do I write in the steady state, DPM conditions UDF, on the particle in the pipeline encountered shield (block block) after the deposition of the trajectory, or a similar UDF can provide to me ? My e-mail:

I would be very grateful

adinurzein June 6, 2013 12:36

Hello guys, I have some problems too to define an injection file while modeling particles hydroninamic using DDPM model and DEM collision. I had defined the injection file using MATLAB. The error message was showing when the calculation process in Fluent advanced the DPM injections. The error:
Updating solution at time level N... done.
Injecting 91125 particles with mass 3.11998e-10 at t = 0
Advancing DPM injections ....
DEM: Memory allocation for collision mesh failed.
Collision mesh width is very small which will give rise to a
huge collision mesh. Consider inspecting your injection setup.
Maybe the number in parcel is not what you want.
Error: Out of memory.
Error Object: #f

Please let me know if you have an idea to fix that error. Thank you very much

cantonuc June 15, 2013 00:57

Dear adinurzein, I have a problem with my research when I'm try to inject initially a huge amount of particle, I'm using a Matlab script to generate the file but it fail in generating the *.inj file for a 3d volume, can you please lend me your script to compare and maybe find the error to my case? Thanks a lot, my email is:

cantonuc June 15, 2013 00:59

Hi Can you lend me the udf too?? I have a similar problem

Thanks a lot

my email


shree272 June 26, 2013 08:01

i am doing combustion modeling for diesel engine, my model is 2D and i am using single particle fuel injection. i defined injection correctly but still while calculation fluent console says "1 particle not found in injection for injection 0" calculation continues but without injection what could be possible error?

Amir1 April 17, 2014 09:43

Hi Guys,

I am working on a study for particle-surface entrapment. I would like to know more about DPM vs DEM.
As you said in DPM, partciles are considered as dots (no volume) and then they interact with the continious phase. What about DEM?
I know both of them use Lagrangian method. DPM for whole particle but DEM for evry single particle.

What is the main difference between DPM abd DEM in terms of considering particle VOLUME or MASS?

Thanks a lot, Amir

Clarence91 July 18, 2014 14:10

Dear adinurzein, could you fix DEM "out of memory" error?
I am working on 2D problem and I get the same error.

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