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-   -   twoPhaseEulerFoam - settings for water droplets in gas (http://www.cfd-online.com/Forums/openfoam-solving/108505-twophaseeulerfoam-settings-water-droplets-gas.html)

majkl October 25, 2012 04:45

twoPhaseEulerFoam - settings for water droplets in gas
 
Hi,

I'd like to ask, how can i set the coefficients of Cvm, Cl, Ct? The case is the flow of water droplets in gas.

Thanks.

Regards,
Michal

sharonyue October 28, 2012 22:12

Quote:

Originally Posted by majkl (Post 388426)
Hi,

I'd like to ask, how can i set the coefficients of Cvm, Cl, Ct? The case is the flow of water droplets in gas.

Thanks.

Regards,
Michal

hi Michal
I have simulate the case u said with interFoam successfully. but I cant simulate a rising bubble with interFoam.
U could try that solver. its simpler than twophaseeulerfoam.

alberto October 29, 2012 02:56

Quote:

Originally Posted by majkl (Post 388426)
Hi,

I'd like to ask, how can i set the coefficients of Cvm, Cl, Ct? The case is the flow of water droplets in gas.

Thanks.

Regards,
Michal

Hi, twoPhaseEulerFoam is the correct choice for your case. The interFoam solver is based on the VOF approach.

For what concerns the values of the coefficients, cvm and cl are pretty much standard (see bubble column tutorial). Ct depends on your flow, and it is important only if turbulence is used.

Best,

majkl October 29, 2012 06:57

Hi,

thanks for answers.

Quote:

Originally Posted by alberto (Post 389017)
For what concerns the values of the coefficients, cvm and cl are pretty much standard (see bubble column tutorial). Ct depends on your flow, and it is important only if turbulence is used.
Best,

Well, for air bubbles in water Cvm 0.5, Cl 0, Ct 1. For water droplets I should use the same coefficients?

If I use Cvm 0, Cl 0, Ct 0, the water cumulates somewhere in the domain, but the behavior of the flow is close to "correct".

With the "bubble case coeffs", the conservation of the mass is OK, but the behavior of the flow is not correct.

Maybe I've wrong setup of the phases. The concentration of water (alpha) is about 1e-5.
  • transportProperties
    Code:

    phasea
    {
        rho            rho [ 1 -3 0 0 0 ] 998.2;
        nu              nu [ 0 2 -1 0 0 ] 0.995e-6;
        d              d [ 0 1 0 0 0 0 0 ] 0.0001;
    }

    phaseb
    {
        rho            rho [ 1 -3 0 0 0 ] 1.2041;
        nu              nu [ 0 2 -1 0 0 ] 1.511e-5;
        d              d [ 0 1 0 0 0 0 0 ] 1;
    }

    Cvm            Cvm [ 0 0 0 0 0 ] 0.5;

    Cl              Cl [ 0 0 0 0 0 ] 0;

    Ct              Ct [ 0 0 0 0 0 ] 1;

  • interfacialProperties
    Code:

    dragModela      SchillerNaumann;

    dragModelb      SchillerNaumann;

    dragPhase      a;


Is there something wrong?

Regards,
Michal

alberto October 29, 2012 11:34

The setup seems correct (droplets are phase a). What coefficient is causing the problem, Cvm or Ct (or both)?

AP

majkl October 30, 2012 05:17

Well, the problem is the Ct coefficient. (I haven't seen any changes with the Cvm 0.5.) I've tried the values 0.0 - 3.0. The "best result" with Ct = 0.2. But the solution is not OK. Mass conservation with 1% discrepancy. The distribution of water phase is strange.

Now, I'm calculating the case in laminar setup (before k-epsilon).

I need more physics in twophaseEulerFoam (TEF) - surface tension and wall adhesion (both implemented in multiphaseEulerFoam - MEF). It is possible to follow MEF with implementation surface tension although the momentum equation in MEF is in conservative form (vs. phase intesive form in TEF)? If you would answer, maybe here, for others.
http://www.cfd-online.com/Forums/ope...eulerfoam.html

Regards,
Michal

Mineral October 30, 2012 22:49

Hi, I am also doing a water droplet simulation in OF, and I am interested in knowing how you defined the droplets into your mesh? I cant figure out the alpha file at the moment

cheers

majkl October 31, 2012 02:41

Hi,

Quote:

Originally Posted by Mineral (Post 389377)
Hi, I am also doing a water droplet simulation in OF, and I am interested in knowing how you defined the droplets into your mesh? I cant figure out the alpha file at the moment

cheers

there is huge demand on the mesh to simulate moving droplets. This is not my way. I set up the input water concentration.

M

Mineral October 31, 2012 05:27

Sorry for stealing your thread, do you mean just by applying uniform alpha distribution at the inlet for an example?

majkl November 1, 2012 04:15

Quote:

Originally Posted by Mineral (Post 389425)
Sorry for stealing your thread, do you mean just by applying uniform alpha distribution at the inlet for an example?

Yes, exactly.

M

Benedikt August 19, 2013 08:46

Hi majkl and others,
I am working on a similar project. I want to simulate a flow of air with waterdroplets (alphaair=0.99998; v(inlet)=50; T=370) into a thin air-filled volume. I solve it with compressibleTwoPhaseEulerFoam. I started with the settings of bubbleColumn and tried different settings, but I am not satisfied with the result. It looks a bit like the volume is empty at the beginning. When streaming into the volume, the inflow doesn't react with the air in the volume. The air in the volume looks like it gets replaced of the inflow, rather than getting suppressed. Did you find any information about the settings of the transportProperties? Or maybe other hints which settings could cause my unphysical behaviour?
Thanks in advance
Benedikt


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