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twoPhaseEulerFoam turbulence model

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Old   May 25, 2012, 07:50
Default twoPhaseEulerFoam turbulence model
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Gerhard Holzinger
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Hello,

I am trying to find out which equations are under the hood of twoPhaseEulerFoam. Most of them can be found in H. Rusches thesis, which is great because to me C++ source code is not self explanatory in the case of fluid dynamics.

I have a question about the turbulence model.

In H. Rusches thesis (page 105, eq. 3.14 and 3.15) the k-equation reads as follows (forgive the LaTeX syntax)

\frac{\partial k_b}{\partial t} + (U_b \cdot \nabla) k_b - and so on ...

but the source code in kEpsilon.H is:

Code:
fvm::ddt(beta, k) + fvm::div(phib, k) + and so on ...
what I would translate into

\frac{\partial \beta k_b}{\partial t} + \nabla \cdot (U_b k_b) - and so on ...

The same is also the case for the epsilon equation. Also the right hand side of both equations seem to have been multiplied by beta.

Code:
... == beta*G - fvm::Sp(beta*epsilon/k, k)
Does anyone know what is the reason for this?

Last edited by GerhardHolzinger; May 25, 2012 at 07:51. Reason: added page and equation numbers
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Old   May 25, 2012, 12:12
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Qingang Xiong
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Quote:
Originally Posted by GerhardHolzinger View Post
Hello,

I am trying to find out which equations are under the hood of twoPhaseEulerFoam. Most of them can be found in H. Rusches thesis, which is great because to me C++ source code is not self explanatory in the case of fluid dynamics.

I have a question about the turbulence model.

In H. Rusches thesis (page 105, eq. 3.14 and 3.15) the k-equation reads as follows (forgive the LaTeX syntax)

\frac{\partial k_b}{\partial t} + (U_b \cdot \nabla) k_b - and so on ...

but the source code in kEpsilon.H is:

Code:
fvm::ddt(beta, k) + fvm::div(phib, k) + and so on ...
what I would translate into

\frac{\partial \beta k_b}{\partial t} + \nabla \cdot (U_b k_b) - and so on ...

The same is also the case for the epsilon equation. Also the right hand side of both equations seem to have been multiplied by beta.

Code:
... == beta*G - fvm::Sp(beta*epsilon/k, k)
Does anyone know what is the reason for this?
Hi GerhardHolzinger,
I also found this difference in twoPhaseEulerFoam. But when I run the code, it seems that no problem. May be you can modify it to standard k-e. Good luck!
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Old   October 16, 2012, 02:25
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Dongyue Li
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Quote:
Originally Posted by GerhardHolzinger View Post
Hello,

I am trying to find out which equations are under the hood of twoPhaseEulerFoam. Most of them can be found in H. Rusches thesis, which is great because to me C++ source code is not self explanatory in the case of fluid dynamics.

I have a question about the turbulence model.

In H. Rusches thesis (page 105, eq. 3.14 and 3.15) the k-equation reads as follows (forgive the LaTeX syntax)

\frac{\partial k_b}{\partial t} + (U_b \cdot \nabla) k_b - and so on ...

but the source code in kEpsilon.H is:

Code:
fvm::ddt(beta, k) + fvm::div(phib, k) + and so on ...
what I would translate into

\frac{\partial \beta k_b}{\partial t} + \nabla \cdot (U_b k_b) - and so on ...

The same is also the case for the epsilon equation. Also the right hand side of both equations seem to have been multiplied by beta.

Code:
... == beta*G - fvm::Sp(beta*epsilon/k, k)
Does anyone know what is the reason for this?
hi , do u know where can I get H. Rusches thesis? or the full name?
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Old   October 16, 2012, 03:59
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Gerhard Holzinger
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Hello,

you can find H. Rusches thesis amongst others at this page:

http://www.foamcfd.org/resources/theses.html
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Old   October 16, 2012, 04:03
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Dongyue Li
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Quote:
Originally Posted by GerhardHolzinger View Post
Hello,

you can find H. Rusches thesis amongst others at this page:

http://www.foamcfd.org/resources/theses.html
thanks! you are online.

by the way, can u recommend me some papers about twophaseeulerfoam?

some of the parameters I dont know the exact mean.
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Old   October 16, 2012, 04:25
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Gerhard Holzinger
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I haven't really found any research papers dealing with the basics of twoPhaseEulerFoam.

H. Rusches thesis is a good point to start digging into the solver. Also the article about bubbleFoam in the OpenFOAM Wiki helps to understand the solver

http://openfoamwiki.net/index.php/BubbleFoam
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Old   October 16, 2012, 04:28
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Quote:
Originally Posted by GerhardHolzinger View Post
I haven't really found any research papers dealing with the basics of twoPhaseEulerFoam.

H. Rusches thesis is a good point to start digging into the solver. Also the article about bubbleFoam in the OpenFOAM Wiki helps to understand the solver

http://openfoamwiki.net/index.php/BubbleFoam
Okay, thank you very much! that would do me alot of favor
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