CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT > Fluent UDF and Scheme Programming

[DPM-UDF] Re-injecting escaping particles at different position

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 10, 2017, 05:12
Default [DPM-UDF] Re-injecting escaping particles at different position
  #1
Senior Member
 
Cees Haringa
Join Date: May 2013
Location: Delft
Posts: 607
Rep Power: 0
CeesH is on a distinguished road
Dear all,

I am currently modeling a system with an external pumped cooling loop. I have no need to model the loop itself explicitly, so it's included as an inlet/outlet system with a forced flowrate. I add massless particles to my system to represent micro-organisms living inside the tank, which have to be tracked for long timespans. These particles can physically enter the cooling loop, and should not leave the system. Hence, I'm aiming to re-inject the particles that leave the outlet at the inlet of the system, to allow for this prolonged tracking without having to resolve the flow-loop completely.

However, I have trouble finding a proper solution to this. Conceptually, I recognize the following possibilities [with issue in brackets]:

DPM_BC at outlet, X particles leave at time t--> surface injection or group injection of X particles at the inlet [but I can not dynamically control the number of streams X in either case]

DPM_BC at outlet, re-inject particles via a file [but this requires dynamic updating of the file to adapt the number of particles, and seems to be a rather slow option computationally as such]

Change TP_POS(tp) and TP_VEL(tp) for particles close to the outlet, to "teleport" them to the inlet [but this simply doesn't seem to work - the position is not changeable directly]


Do any of you have any (conceptual) solutions to this problem?

Best regards,
Cees
CeesH is offline   Reply With Quote

Old   May 13, 2020, 06:47
Default
  #2
New Member
 
Ullas P K
Join Date: Jan 2017
Posts: 10
Rep Power: 9
ullaspk1990 is on a distinguished road
Quote:
Originally Posted by CeesH View Post
Dear all,

I am currently modeling a system with an external pumped cooling loop. I have no need to model the loop itself explicitly, so it's included as an inlet/outlet system with a forced flowrate. I add massless particles to my system to represent micro-organisms living inside the tank, which have to be tracked for long timespans. These particles can physically enter the cooling loop, and should not leave the system. Hence, I'm aiming to re-inject the particles that leave the outlet at the inlet of the system, to allow for this prolonged tracking without having to resolve the flow-loop completely.

However, I have trouble finding a proper solution to this. Conceptually, I recognize the following possibilities [with issue in brackets]:

DPM_BC at outlet, X particles leave at time t--> surface injection or group injection of X particles at the inlet [but I can not dynamically control the number of streams X in either case]

DPM_BC at outlet, re-inject particles via a file [but this requires dynamic updating of the file to adapt the number of particles, and seems to be a rather slow option computationally as such]

Change TP_POS(tp) and TP_VEL(tp) for particles close to the outlet, to "teleport" them to the inlet [but this simply doesn't seem to work - the position is not changeable directly]


Do any of you have any (conceptual) solutions to this problem?

Best regards,
Cees

Did you find an answer to this. I am also trying to get an idea regarding the same. It would be helpful if anyone can suggest some methods. Thanks in advance
ullaspk1990 is offline   Reply With Quote

Old   May 13, 2020, 07:12
Default Simulation
  #3
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 35
vinerm will become famous soon enough
It depends on whether the simulation is steady or transient. If it is steady, then it does not really make sense to transfer particles from the outlet to the inlet. If it is transient, then it does make sense because number of particles will increase slowly. However, since the particles are massless, they do not add any value. So, 100 particles or 1000 particles are all the same. Except that you will be able to see 1000 particle tracks.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   May 13, 2020, 09:30
Default
  #4
New Member
 
Ullas P K
Join Date: Jan 2017
Posts: 10
Rep Power: 9
ullaspk1990 is on a distinguished road
Quote:
Originally Posted by vinerm View Post
It depends on whether the simulation is steady or transient. If it is steady, then it does not really make sense to transfer particles from the outlet to the inlet. If it is transient, then it does make sense because number of particles will increase slowly. However, since the particles are massless, they do not add any value. So, 100 particles or 1000 particles are all the same. Except that you will be able to see 1000 particle tracks.
Thank you for the reply. I am trying to do unsteady simulation and I want to inject a particular number of particles and then I will maintain the amount of particles constant but I need to re-circulate the particles escaped from the outlet. The re-circulation of escaped particles from the outlet is the problem I am facing now.
ullaspk1990 is offline   Reply With Quote

Old   May 13, 2020, 09:34
Default Objective
  #5
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 35
vinerm will become famous soon enough
Why do you want particles to recirculate? It's the objective of doing this that defines the approach to be used.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   May 13, 2020, 10:06
Default
  #6
New Member
 
Ullas P K
Join Date: Jan 2017
Posts: 10
Rep Power: 9
ullaspk1990 is on a distinguished road
Quote:
Originally Posted by vinerm View Post
Why do you want particles to recirculate? It's the objective of doing this that defines the approach to be used.
I am actually working on air purification. So I am passing the air with particles through a filter and the remaining particles which escaped through the outlet need to be recirculated. Thanks in advance
ullaspk1990 is offline   Reply With Quote

Old   May 13, 2020, 10:16
Default Define_dpm_bc
  #7
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,946
Blog Entries: 1
Rep Power: 35
vinerm will become famous soon enough
You can use UDF, DEFINE_DPM_BC. It acts on those particles that hit a particular boundary where the function is hooked. Within this UDF, you can change the positions of all the particles to their initial injection position. Look at

https://www.afs.enea.it/project/nept...udf/node66.htm
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   May 13, 2020, 10:34
Default
  #8
New Member
 
Ullas P K
Join Date: Jan 2017
Posts: 10
Rep Power: 9
ullaspk1990 is on a distinguished road
Quote:
Originally Posted by vinerm View Post
You can use UDF, DEFINE_DPM_BC. It acts on those particles that hit a particular boundary where the function is hooked. Within this UDF, you can change the positions of all the particles to their initial injection position. Look at

https://www.afs.enea.it/project/nept...udf/node66.htm
Thank you very much for your help. I will try this way.
ullaspk1990 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
initialize particles position in kinematiccloudpositions chpjz0391 OpenFOAM Running, Solving & CFD 1 May 25, 2020 03:26
[DPM problem] infinite particles loop in domain (twin cyclone - double cyclone)) ghost82 FLUENT 6 May 19, 2020 14:19
export a position contour on a surface for tracked particles tsh850227 CFX 0 April 14, 2016 03:30
Accessing the position and diameter of lagrangian particles ahcai007 OpenFOAM Programming & Development 3 March 31, 2014 19:22
DPM UDF particle position using the macro P_POS(p)[i] dm2747 FLUENT 0 April 17, 2009 01:29


All times are GMT -4. The time now is 10:20.