[Stefanie.S.W.]

Hello everybody,

I need a little help with understanding more about the transport properties in a multiphaseEulerFoam case.

Here is a link to a standard transport properties dict for multiphaseEulerFoam:
https://github.com/OpenFOAM/OpenFOAM...portProperties

After some reading and try and error I figured that I better understand every function of this dict.

I understand the phase properties (line 18-75) except for the
constantCoeffs (line 28)
In my case I will assume constant diameters so I did not worry about possible diameter models.

I also understood how I can turn interface compression (line 84-89) on (1) or off (0) to maintain a sharp interface. I thought, mixing occurs when I do not maintain a sharp interface - but that turned out to be wrong.

I understand sigma (line 77-82) as interface tension. But I do not understand how it can be the same value for different fluids.

The drag is my main parameter to describe (eg) mixing (beginning at line 95). I read about the 11 diameter models, like SchillerNaumann or Syamlal-OBrien - but as I understand in a turbulent flow with a high reynolds No they compute about the same coefficients.
What I find most confusing is the residualPhaseFraction and the residualSlip
- why do they exist twice, per phase in a mixing and for the mixture?

I am sorry for the big amount of questions and hope you can explain some of the functions in the transportProperties dict to me.

Thank you very much =)

----------------------------------------------------------

I am mixing oil, water with a surfactant (soap) and air. But I can neglect the bubbles or foam of water, soap and air. Also I have some experimental data so that I can calibrate my values. My case is an easy geometry without an inlet or outlet and it is a pretest in order to calibrate my solver. I did not provide dicts of my case, because my questions are about general understanding of the transportProperties dict.

[Stefanie.S.W.]

I continued my research and would like to share my two favorite free sources with you:

http://www.tfd.chalmers.se/~hani/kur...oam_peered.pdf

http://www.tfd.chalmers.se/~hani/kur...a_Oruganti.pdf

They helped me with general understanding.

[Stefanie.S.W.]

Hello,

I briefly documented what I found out.
Now I have two remaining questions:

Does the convergence criteria of the dragModel depend on the particle diameter?

Why is the default surface tension 0,07 for quite different phases? Does it depend on wall friction or only interfacial friction?

Please correct me if I provided wrong information for the following code fractions:

phases
(
water //phaseProperties
{
nu 1e-06;
kappa 1e-06;
Cp 4195;
rho 1000;

diameterModel constant; //for lagragian particles within an eulerian phase
constantCoeffs //you can also apply a diameter model
{
d 1e-3;
}
}
[...]
);

sigmas //surface tension in [N/m] - only defined when interfaceCompression is on
(
(air water) 0.07
(air oil) 0.07 //I found 0.02-0.03 ?
[...]
);

interfaceCompression //interface sharpening - on/off switch: 0= dispersive flow, 1=VoF approach
(
(air water) 1
(air oil) 1

);

virtualMass //mass of continuous phase carried by particles during flow through continuois phase -> generates Force : F=rho_continuous*Cvm*V_particle*a_relative
( //default for Cvm=0.5
);

drag //caused by relative motion between phases
(
(air water)
{
type blended; //11 models? // blended means that continuous and dispersed phase can reverse - different models for each phase possible

air
{
type SchillerNaumann; //model for phase 1
residualPhaseFraction 0; //convergence criterion
residualSlip 0; //convergence criterion
}

water
{
type SchillerNaumann; //model for phase 2
residualPhaseFraction 0;
residualSlip 0;
}
//convergence criteria for coupling
residualPhaseFraction 1e-3;
residualSlip 1e-3;
}

[...] // I had to define all phase pairs to start the simulation

);


// This is a dummy to support the Smagorinsky model
transportModel Newtonian;
nu [0 2 -1 0 0 0 0] 0;


// ************************************************** *********************** //

[Stefanie.S.W.]

Hello everyone,

I need your help!
I mixed oil (white) and water (blue) using multiphaseEulerFoam. Air (red) is present, gravity is on and I defined a default atmosphere for all tops.
When oil and water are mixed together the volume of this mixture is less than the sum of both phases. In the end of the simulation the phases are (mostly) separated and the volumes are ok. I do not understand why the volume is compressed in the beginning.
Also I do not understand why the separation of oil and water takes so long. In the related experiment it took 50sek at the most. (The oil diameter of 0.7mm equals the sauter diameter from the experiment).

Interface sharpening is on, and the phases are separated in the end. So I believe that the increase of volume is not due to a deposition of air. I used default values for transport properties and LES Smagorinsky for turbulence.
Thank you for your advice and suggestions!

Attached you find images at time=2sek, time=10se, time=50sek and time=150sek.
Also this is my transportProperties dict:

FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

phases
(
water
{
nu 1e-06;
kappa 1e-06; //Isentropenexponent
Cp 4195; //Wärmekapazität
rho 1000;
diameterModel constant;
constantCoeffs
{
d 1e-3;
}

}
oil
{
nu 7.6e-06;
kappa 1e-06;
Cp 4195;
rho 876;
diameterModel constant;
constantCoeffs
{
d 0.0007;
}
}
air
{
nu 1.48e-05;
kappa 2.63e-2;
Cp 1007;
rho 1;
diameterModel constant;
constantCoeffs
{
d 3e-3;
}
}
);

sigmas
(
(air water) 0.07
(air oil) 0.07
(oil water) 0.07
);

interfaceCompression
(
//(air water) 1
(air oil) 1
(oil water) 1
);

virtualMass
(
);

drag
(
(air water)
{
type blended;
air

{

type SchillerNaumann;

residualPhaseFraction 0;

residualSlip 0;

}

water

{
type SchillerNaumann;
residualPhaseFraction 0;
residualSlip 0;
}

residualPhaseFraction 3e-3;
residualSlip 3e-3;

}

(air oil)
{
type blended;
air

{
type SchillerNaumann;
residualPhaseFraction 0;
residualSlip 0;
}

oil

{
type SchillerNaumann;
residualPhaseFraction 0;
residualSlip 0;
}

residualPhaseFraction 1e-3;
residualSlip 1e-3;

}
(oil water)
{
type blended;
water

{
type SchillerNaumann;
residualPhaseFraction 0;
residualSlip 0;
}

oil

{
type SchillerNaumann;
residualPhaseFraction 0;
residualSlip 0;
}

residualPhaseFraction 1e-3;
residualSlip 1e-3;

}
);

// This is a dummy to support the Smagorinsky model
transportModel Newtonian;
nu nu [ 0 2 -1 0 0 0 0 ] 0;

[Himanshu_Shrivastava]

Hi,

right now i am studying multiphase.

need your help in multiphasEulerianFoam in dam break example?

does d in transport properties of multiphaseEulerianFoam is diameter?

and how does it affect damBreak simulation as it does not have any dispersed phase of which we need to give diameter value.
All the phase are continuous in nature.

Thank You