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Old   January 17, 2010, 19:25
Default Multiple Fluid Flow
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Brian Pal
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Hello,

I am new to both Fluent and this forum, so please forgive my lack of familiarity with the software. I have worked through the applicable tutorials on the customer portal, listened to some of the webinars, and have searched extensively on this forum, but I can't seem to figure out how to setup a simulation I am working on.

I am modeling a situation where I have a glassware tube with a flow of hydrogen coming into the bottom port, a flow of argon coming down into the top port, and both gasses are exiting through the side port which is at atmospheric pressure.

Please see the attached image of the geometry/mesh that I am working with. I have employed symmetry and have created a 'named selection' for each of the inlets, the symmetry plane, and the wall group.

My main question is how do I specify the different fluids coming into each of the ports? I have been assuming that I need to use a multiphase model, and have been trying to use the eulerian model but haven't been able to put it all together. Also, I am assuming that I need to define the cell zone conditions, but I don't know what the composition of the cell zone is going to be as the two flows will be interacting.

Also, I would like to create a ~200mm zone below the side port which will model a furnace surrounding the glassware. I am assuming that I need to create a different wall group for that section and just create a temperature boundary condition with the energy model turned on?

Thanks much for any help,

Brian Pal
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Old   January 18, 2010, 01:38
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Brian,

If ur not dealing with different phase (liquid vs gas ) u are not require to use multiphase modeling.
Go Defind>Models>Species>Transport & Reaction, choose species transport.
Goes to drop down menu "Mixture Material" then select the material u wanna mix.
if its don't appear there, click edit to choose it urself.

After u setting this, at the boundary condition setup u will have a "species" bar appear. for example, u create a pressure inlet, u will see a bar call "species", goes into species, select the argon flow u created and put it as "1" .
0 means no argon, 1 mean pure argon.

Take a try.
u may refer to fluent user guide on "species transport without reaction" also.
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Old   January 21, 2010, 06:30
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Quote:
Originally Posted by herntan View Post
Brian,

If ur not dealing with different phase (liquid vs gas ) u are not require to use multiphase modeling.
Go Defind>Models>Species>Transport & Reaction, choose species transport.
Goes to drop down menu "Mixture Material" then select the material u wanna mix.
if its don't appear there, click edit to choose it urself.

After u setting this, at the boundary condition setup u will have a "species" bar appear. for example, u create a pressure inlet, u will see a bar call "species", goes into species, select the argon flow u created and put it as "1" .
0 means no argon, 1 mean pure argon.

Take a try.
u may refer to fluent user guide on "species transport without reaction" also.
Dear all and dear Herntan,
I am also working on heavy gas dispersion modeling using Fluent (Dispersion of CO2 in air). Regarding to your reply you sended to Brian Pal,what do you mean by
"u will see a bar call "species", goes into species, select the argon flow u created and put it as "1" .
0 means no argon, 1 mean pure argon." I see only one bar under "species mass fraction" that was set as 0 as default. You mean I should make this 1? If not, what if the species mass fraction is let as zero or another value?
Secondly, I began the simulations, but CO2 residual is alwasy 0 (zero). Do you think I made a mistake in somewhere?
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Old   January 21, 2010, 21:44
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If u want that inlet to be pure CO2 flow, put it as 1.
Its not bar, its a tab. I don't think its easily get wrong since there is no other option on species in boundary condition.

Cannot understand ur residual question, post picture and give more detail if u REALLY want to ask question.
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Old   January 22, 2010, 06:31
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Thank you Herntan,
Residual question: When you run your simulation, the values of iteration no., velocity, continuity, k,epsilon.... residuals are written in each simulation. Please see below the residual values of three subsequent itaretions in my simulation in which the value of CO2 is zero in each time. This is a 3-D simulation. In 2-D simulation, I have no such problem and the residual values for CO2 has some value other than zero, like the other residulas. I checked all settings again and again and then started the simulation again and again. But in my 3-D simulations, I never get the residual values other than zero.
Many thanks for your reply.
itercontinuityx-velocity y-velocityz-velocitykepsilonco290037.65E-054.19E-085.21E-095.24E-095.37E-082.03E-070.00E+0090047.64E-054.23E-085.31E-095.27E-095.36E-082.03E-070.00E+0090057.61E-054.21E-085.24E-095.25E-095.36E-082.01E-070.00E+00
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Old   January 22, 2010, 06:35
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Hope this time the values can be read properly. If not, please set the values one under the other, according to their color. Iteration numbers are 9003, 9004 and 9005.
itercontinuityx-velocity y-velocityz-velocitykepsilonco2

90037.65E-054.19E-085.21E-095.24E-095.37E-082.03E-070.00E+00

90047.64E-054.23E-085.31E-095.27E-095.36E-082.03E-070.00E+00

90057.61E-054.21E-085.24E-095.25E-095.36E-082.01E-070.00E+00
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Old   January 22, 2010, 07:06
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Residual is used to check the calculation convergence.
If its 0 , i guess the CO2 guess not even exist inside ur simulation.

Try to snap shot ur model look and setting u had done.
Its very hard to help u without any image.
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Old   January 24, 2010, 10:52
Exclamation Multiple Fluid flow
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Hi,
The geometry i m using have two different fluids (Ar and N2). IT has 3 inlet and 1 outlet. The flow is laminar.
I want to know how m i suppose to modell it.
inlet 1 is Ar
inlet 2 is Ar
inlet 3 is Ar+N2/N2

i dnt know how to update properties of fluids.

If i use a single fluid then i can write a UDF for properties.
But i m nt able to find a method to update properties(UDF) for mixture of fluids.

I dnt know whether i have to write UDF for N2 and Ar or UDF for AR+N2 or UDF for AR, N2 and Mixture.

Can any one please help me. As i have read USEr guide and tutorial.
But all in vain

Reply asap.

Thanks
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Old   January 28, 2010, 13:49
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hi sang follow this procedure
after u upload ur model in fluent do this go to;
define-> models-> species-> transport& reaction-> species transport
then press ok n ok n u will be at main menu
now go to
materials-> fluent data base-> (change to fluid in material type, select the material u need and hit on)"copy"(i think u need 3 times Ar so u shud copy that material 3 times and N2 once)-> change/create-> ok
then again go back to:
define-> models-> species-> transport& reaction-> species transport-> eidt(its at right of "mixture material")-> edit(right of mixture species)-> add the materials u want into "selected species"(note- keep one extra material such as air)-> ok
now boundary conditions:
define->boundary conditions-> inlet1->(when u open this u have various opetios such as momentum, thermal, radiation, species...
select on species and just hit 1(in place of 0) to the right of material u need to flow through that in let)
for two materials to flow hit 0.5 on Ar and 0.5 on N2
n u are all set as of i know
let me know if hav any porblem see u bye
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