CFD Online Discussion Forums

CFD Online Discussion Forums (
-   FLUENT (
-   -   Injection of specific number of particles in DPM (

DH October 20, 2006 23:41

Injection of specific number of particles in DPM
Hi, I am trying to inject specific number of particles on a wall boundary with 3-D DPM model. I am running Fluent in windowXP.

Could anyone tell me if I can use the DEFINE_DPM_INJECTION_INIT to specify

1. the number of particles

2. location of injection

3. particle size

I tried to follow the 4.6.5 Fluent UDF manual. But, it is not the the similar case with the model I want to make. I just want to inject solid particles on the wall surface & track them in 3-D airflow.

If you tell me any way to inject specific number of particles, it would be great?

If possible, could you send me simple code doing this?

Thank you ahead


Allan Walsh October 23, 2006 12:09

Re: Injection of specific number of particles in D
Why are you using a UDF to do this? Why don't you just use the Set Injection menu? Or if your set-up is more complicated, make a file with particle data and read that in - according to the specifications given in the manual.

DH October 23, 2006 15:17

Re: Injection of specific number of particles in D
Thank you for the reply, Allan. You are right. I can use the group injection panel to inject specific number of particles.

But I would like to ask you how I can inject specific number of particles having different diameters. For example, if I want to inject 10 paricles of 1 micron and 5 particles of 10 micron in a specific location, how can I manage it?

Also, the manual was saying "looping over particle". Does that mean I first inject particles in the specific location then adjust parameters such as particle diameter or density by using UDF function? Sorry, I am a novice and confused.

Could you help with this? Thanks ahead


Allan Walsh October 27, 2006 15:18

Re: Injection of specific number of particles in D
Make two injections - particles of 1 micron and particles of 10 microns. Why does the particle diameter change? If reacting, then you need to set up specific laws. In general, the UDF's are not for novices.

DH October 27, 2006 15:48

Re: Injection of specific number of particles in D
You mean I can make different two injections on the same location?

Abigail October 30, 2006 09:35

Re: Injection of specific number of particles in D
Yes you can, for each injection you specify the particle position, velocity, diameter, mass flow. If you wish to keep the position the same for several injections you can.

It is also possible to do a group injection and specify a range of diameters.

sfotovati July 12, 2010 13:55

how can I increase the number of injected particles?
Dear users,
I know that the maximum number of injected particles from any surface is equal to the total number of mesh points over that surface. is there any way that I can increase the injected particles number more than number of cells?

snow July 13, 2010 02:49

Why not use file injection?

Gold October 18, 2011 12:58

Injection for a while but once from each point
i am doing some resuspension study, i am doing unsteady simulation and the effect of flow on resuspension, i use UDF for knowing whether the removal force of particles are enough for resuspension or not but the problen is injection takes place several times from one point but in reality the amount of particles in each cell are limited and once they resuspend it should not exist there?

do you please give me some idea about this situation?


doronzo October 18, 2011 15:02


One thing, I think, important to keep in mind in this discussion is that Lagrangian particles here are clusters of particles, and the total number of clusters calculated in a DPM solution is related to mesh and time step. The total mass injected in time (kg/s) is thus subdivided in a discrete number of clusters, and this number is the number of cells through which the injection occurs. If I want to inject for example 10 particles, probably I need a boundary that has 10 cells; in that case, the number of clusters corresponds to the actual number of particles I want to track. What do you think?


Sushilkumar October 20, 2011 02:35

You can use 'Random Walk Model' to increase the number of particles in multiple of the cells you have on a specified surface. e.g. for 10 cells you and define the number of tries in Random walk model as 5 and you will get 50 particles.

doronzo October 20, 2011 07:50

50 particles, or 50 clusters of particles?

In other words, given the total mass of solid to be injected, is that mass subdivided in 50 entities? (in a specific time)


ffsun March 16, 2016 22:04

Could you tell me how to write injection file ?

Actually i know the format of the file,but the question is: if i want to injection a large number of parcels,i will write and write so many lines,and i don't know the x y z position the parcels should be.

If i use surface file,it should be on core of every mesh,but how to get every core's coordinate?

and how to write this file using c language ?


All times are GMT -4. The time now is 16:46.