CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

mixing fresh-saltwater

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 6, 2014, 08:16
Default mixing fresh-saltwater
  #1
New Member
 
dell-ocqa aronne
Join Date: Feb 2014
Posts: 4
Rep Power: 12
aronne030389 is on a distinguished road
Hi, i'm really new to OpenFoam and i'm looking for a solver that can simulate the mixing between salt water and fresh water. In principle it's just one phase and i have to solve the transport equation for the solute (NaCl) that affects the density,there's any specific solver??. I look to interMIxingFoam putting phase2 fresh and phase3 salt water and setting the diffusion coeff between them. But i don't understand the physic behind this solver : that coeff of diffusion can be treat as molecular diffusion ? which is the transport equation that rule the process? ... and what about twoLiquidMixingFoam....thanks very much
aronne030389 is offline   Reply With Quote

Old   February 6, 2014, 08:47
Default
  #2
New Member
 
Tommy V
Join Date: Nov 2013
Posts: 29
Rep Power: 12
Villo is on a distinguished road
Hi aronne,
i think twoLiquidMixingFoam is perfect for your issue.
Is a solver for mixing between two fluids (single phase) with different diffusion properties.
You will see that the transport equation will use the scalar alpha as ratio between the two different densities.
You can explore the solver here
applications/solvers/multiphase/twoLiquidMixingFoam/
Tommy
Villo is offline   Reply With Quote

Old   February 6, 2014, 14:41
Default
  #3
New Member
 
dell-ocqa aronne
Join Date: Feb 2014
Posts: 4
Rep Power: 12
aronne030389 is on a distinguished road
Hi Tommy Thank you,
i loked into the solver folder. Am i right saying that i can consider molecular diffusion between saltwater and freshwater as the Dab coefficients to set in the transportPropertiesDict?? then there's also a turbulence diffusion ( alphatab*turbulence->nut() ) that in my work i will not consider since my flow are laminar.

FROM fille
AlphaDiffusionEqn.H

{
fvScalarMatrix alpha1Eqn
(
fvm::ddt(alpha1)
- fvc::ddt(alpha1)
- fvm::laplacian
(
volScalarField("Dab", Dab + alphatab*turbulence->nut()),
alpha1
)
);

alpha1Eqn.solve();

alpha2 = 1.0 - alpha1;
rhoPhi += alpha1Eqn.flux()*(rho1 - rho2);
}

rho = alpha1*rho1 + alpha2*rho2;
aronne030389 is offline   Reply With Quote

Old   February 6, 2014, 15:01
Default
  #4
New Member
 
Tommy V
Join Date: Nov 2013
Posts: 29
Rep Power: 12
Villo is on a distinguished road
This is the ./constant/transportProperties for twoLiquidMixingFoam
https://github.com/OpenFOAM/OpenFOAM...portProperties
You will see Dab [0 2 -1 0 0 0 0], or else [m^2/s]: yes, that's the molecular diffusivity.
About nut: yes, if you're in laminar you can also delete it.
Villo is offline   Reply With Quote

Old   February 11, 2014, 11:34
Default
  #5
New Member
 
dell-ocqa aronne
Join Date: Feb 2014
Posts: 4
Rep Power: 12
aronne030389 is on a distinguished road
thank you so much , it seem to work. Have a nice job!!
aronne030389 is offline   Reply With Quote

Old   February 11, 2014, 11:40
Default
  #6
New Member
 
Tommy V
Join Date: Nov 2013
Posts: 29
Rep Power: 12
Villo is on a distinguished road
Quote:
Originally Posted by aronne030389 View Post
thank you so much , it seem to work. Have a nice job!!
cool! I had to work a lot on that solver, if you need any help (principally via LES models) just ask.
have fun!
Villo is offline   Reply With Quote

Old   January 7, 2020, 10:36
Default
  #7
Senior Member
 
Join Date: Jul 2019
Posts: 148
Rep Power: 6
Bodo1993 is on a distinguished road
Quote:
Originally Posted by Villo View Post
cool! I had to work a lot on that solver, if you need any help (principally via LES models) just ask.
have fun!

Dear Villo,

I use twoLiquidMixingFoam solver in OpenFOAM. In my setup, I have a single inlet and two outlets as shown in the attachment. The two fluids are expected to mix and exit through the outlets.
I am wondering what would be the boundary conditions for the alpha phase in this case.
I use zeroGradient or inletOutlet. Initially, it works fine since only single phase exists at the outlet boundary. However, when a mixed phase reaches the outlet boundary, I get some vortices (see attachment).
In the zero directory, I have three files only; p_rgh, U and alpha.phase1.
I would appreciate any assistance.
Thanks.
Attached Files
File Type: pdf Forum2.pdf (178.5 KB, 27 views)
Bodo1993 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
What's is mixing law richard ben FLUENT 4 September 25, 2014 18:30
The mixing of freshwater and saltwater yinyueqiang FLUENT 0 February 18, 2013 00:07
Problem with Mixing plane Mitpostdoc FLUENT 0 July 26, 2011 15:31
Meshing a Mixing Plane using ICEM Will Anderson FLUENT 0 November 6, 2010 18:08
Mixing plane geometry definition Hbet FLUENT 0 January 18, 2002 08:16


All times are GMT -4. The time now is 15:24.