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

modeling tracer transport in liquid

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 5, 2013, 08:17
Default modeling tracer transport in liquid
  #1
Member
 
Join Date: Feb 2013
Posts: 31
Rep Power: 13
cinwendy is on a distinguished road
Hi all,

I wish to simulate tracer solute within moving liquid using FLUENT. The tracer is inert ion/molecule solule in liquid water. I have difficulty in matching what I understand about a liquid solution with CFD model(s). I didn't get much clue from the user manuals, and I am still unsure about the power of UDF or other hidden techniques, if applicable.

The first part of my question:
Conceptually, the molecule/ion is soluble in liquid water. Since they are not too much by volume and is not "continuous", so it should not be Eulerian model. Since they are actually a huge amount of molecules, which size is too small and amount is too large, it seems that it is also not Lagrangian model. I checked the species transport model and found a list of gaseous mixture build-in, including a mixture of inert gas model. But my system is in liquid water, and I am thinking only a single species of tracer solute, I doubt that can be used.

How can I "define" a new species, and let it "goes" with water?
From CFD perspective, is this a multiphase problem or a species transport problem?

The second part of my question:
After I get this new species get along with water, I would like to alter the BC. The command list in "Calculation Activities" is what I am thinking, as I came over lines like "define bc mass-flow-inlet inlet water y n 0" when going through some tutorials. I looked around for explanation about the syntax and arguments for it but in vain. Anyone know where shall I look for it? (I see some examples in the forum, but would like to learn how to use them)

Thank you in advance!
cinwendy is offline   Reply With Quote

Old   March 5, 2013, 10:52
Default
  #2
Senior Member
 
A CFD free user's Avatar
 
A-A Azarafza
Join Date: Jan 2013
Posts: 226
Rep Power: 14
A CFD free user is on a distinguished road
Hi
Species transport model is what you need. however, you can use UDS too, but you don't need any UDF. If you use species transport, you also should define a tracer. The tracer properties are the same as water, so there is no need to define new material. You need to define a mixture and adjust parameters for the defined mixture. The only thing remains is to define inlet and out let and suitable boundary conditions. The trick for a puls injection is that you set tracer mass fraction in inlet equal to 1 then do 1 or 2 iterations, then set it again to 0 and keep going to get convergency. To get a curve for the tracer behavior, usually mass fraction vs iteration or time, you should go to monitor -surfaces and define appropriate surfaces and set whether you need time or iteration. Finally, turn it on as simulation begins.
I might give you more info later if you need.
Good luck
A CFD free user is offline   Reply With Quote

Old   March 5, 2013, 12:30
Default
  #3
Member
 
Join Date: Feb 2013
Posts: 31
Rep Power: 13
cinwendy is on a distinguished road
Thank you very much!! I am going to try it out. Hopefully I will be back here with some good news next time.

And, yes. I would like to know more about this in near future.
cinwendy is offline   Reply With Quote

Old   March 6, 2013, 06:40
Default
  #4
Member
 
Join Date: Feb 2013
Posts: 31
Rep Power: 13
cinwendy is on a distinguished road
Hi,

I have tried it out. I set the inlet BC as told. However, from the results it seems that the tracer mass fraction is also originally 1 within the interior cell zone. So the simulation looks more like there were constant tracer going in and out before simulation starts and then until 0.02 s later there is no more from the inlet. If I set the cell zone condition to fluid (not mixture) then the 'species' part dissapeared totally. Can you tell me how to set the interior tracer concentration to zero when I start the simulation? Thank you!
cinwendy is offline   Reply With Quote

Old   March 6, 2013, 12:08
Default
  #5
Senior Member
 
A CFD free user's Avatar
 
A-A Azarafza
Join Date: Jan 2013
Posts: 226
Rep Power: 14
A CFD free user is on a distinguished road
I suppose you patch a constant mass fraction for the zone. It's not what I meant. You have to change the mass fraction as I told you in boundary condition. Go to
define/ boundary condition, species transport and set the value for the tracer equal to 1, then do one iteration and again reset it to 0 and start your simulation till get the converged result. So I think you went the wrong path. If you have any more questions contact me:
aboozar.azarafza@gmail.com

Last edited by A CFD free user; March 6, 2013 at 13:57.
A CFD free user is offline   Reply With Quote

Reply


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
Modeling Liquid Liquid droplet flow Mircro_fluidics_ STAR-CCM+ 7 November 14, 2017 03:51
tracer transport using tri mesh? kpax OpenFOAM Running, Solving & CFD 2 November 16, 2012 05:49
Modeling two liquid flow mixture hamideh FLUENT 0 June 13, 2011 11:44
Dynamic sloshing and hydrodynamic modeling of liquid storage tank for earthquake K i M Main CFD Forum 14 April 22, 2011 23:24
species transport and discrete phase modeling .... farhath FLUENT 2 February 11, 2006 02:09


All times are GMT -4. The time now is 04:18.