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-   -   Controlling Number of particles in Surface Injection (DPM) (http://www.cfd-online.com/Forums/fluent/104532-controlling-number-particles-surface-injection-dpm.html)

santoshroopak July 11, 2012 14:39

Controlling Number of particles in Surface Injection (DPM)
 
Hi,

I am trying to inject a specific number of particles(say 5000) from a surface using surface injection in FLUENT, but the number of mesh faces on that surface is only 400. Is there a way I can use surface injection and still get 5000 particles without changing the mesh.

I am not sure if this question was answered earlier, but I couldn't find it in the forum. Any help would be greatly appreciated. Thanks.

shk12345 July 12, 2012 01:44

hii

I am also doing something similar, but i don't know whether there is any way to do it in that fashion.
One thing can be done, you can use file injection instead of surface and provide the location of 5000 points in that file.
Or use to switch on the sophisticated tracing in turbulence in dpm . I think that increase the particle injection. Also if u r using the rosin-rammer , increase number of diameter . It will increase the number of particles injections.
Try it out adn let me know . otherwise i will look in detail into this problem

Regards
Shk

santoshroopak July 12, 2012 19:10

Hello Shk,

I am trying a file injection, but I may have to increase the particles still more later on and using file injection would be cumbersome then. Also, I am very much curious to know if this is possible with surface injection. Thanks.

Santosh

shk12345 July 13, 2012 00:04

Yes i think it is also possible via surface injection.

In rosin-Langmuir increase the number of diameter
and use turbulence model with sophisticated tracing to get the increased number of particle injection.

shk

santoshroopak July 13, 2012 15:51

Hello Shk,

I have a new problem. I am trying file injection and it is giving me an error. Can you please help me with this? The sequence of steps that I follow are as follows:

1. I create a *.inj file with the following format:

((x y z u v w diameter temperature mass-flow) name)
((-144.999551 40.818547 -75.547331 0 0 0 0.000001 311.33 0.001) 0)
((-144.999551 40.818547 -75.547331 0 0 0 0.000001 311.33 0.001) 1)
..............

2. I save the file in the same directory as my case and data file.

3. In fluent, in set injection panel, I choose injection-type as file and then select my *.inj file.

4. When I try to list the injection, it doesn't detect any particles and it gives the following message.

Particle streams from injection:
STREAM ...........................INITIAL VALUES...........................
NO TYP (X) (Y) (Z) (U) (V) (W) (T) (DIAM) (MFLOW)

and I assume that the injection failed. I understand that I am doing something fundamentally wrong, but I am not able to figure it. Can you please guide me with this procedure?

Thanks.

Roopak

shk12345 July 14, 2012 00:02

hi
In the above injection file your velocities are 0 0 0. Try to give some velocity and then check your case . hope it will run.
Also the particle dia seems to be too small.
the injection:name has to be put there instead of numbers at the last.
The syntax is
((x y z u v w dia temp mass-flow-rate) injection:name)

hope that will work

shk

VictorLP April 27, 2013 14:56

I have a similar with Santoshroopak problem.
Quote:

1. I create a *.inj file with the following format:

((x y z u v w diameter temperature mass-flow) name)
((-144.999551 40.818547 -75.547331 0 0 0 0.000001 311.33 0.001) 0)
((-144.999551 40.818547 -75.547331 0 0 0 0.000001 311.33 0.001) 1)
..............

2. I save the file in the same directory as my case and data file.

3. In fluent, in set injection panel, I choose injection-type as file and then select my *.inj file.

4. When I try to list the injection, it doesn't detect any particles and it gives the following message.

Particle streams from injection:
STREAM ...........................INITIAL VALUES...........................
NO TYP (X) (Y) (Z) (U) (V) (W) (T) (DIAM) (MFLOW)
There are no another data when i make a LIST.
I have 2D case and i have no Z and W and therefore i excluding it from the file.



The problem is not due to zero velocities that written above . May be somebody can give a valid injection file?
Thanks in advance, Victor.

yoooodarulez August 3, 2013 12:17

I presume that you must have found a solution to this problem but i was wondering,since im having a similar problem at the moment,if increasing the number of planes injecting particles,and therefore increasing particles injected and splashed,is physically correct and viable.For my case i am injecting particles of rain into the mainstream of air towards a wing,not from the inlet but from a created plane in front of the wing.So i was wondering if it would be correct to create multiple planes on top of each other so that i can get more particles injected and consequently splashed.Then again i dont know what would be the correct value of total mass flow rate though


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