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-   -   Kunz phase change model and what is done (http://www.cfd-online.com/Forums/openfoam-solving/73006-kunz-phase-change-model-what-done.html)

romant February 24, 2010 05:37

Kunz phase change model and what is done
 
Hej,

I have a couple of questions about how the phase change models in interPhaseChangeFoam work.

First:
There are two functions within the solver mDotP() and mDotAlphal()
mDotP()'s description is like this
Code:

//- Return the mass condensation and vaporisation rates as an
//  explicit term for the condensation rate and a coefficient to
//  multiply (p - pSat) for the vaporisation rate

What does this exactly mean?

The same goes for mDotAlphal()
Code:

//- Return the mass condensation and vaporisation rates as a
//  coefficient to multiply (1 - alphal) for the condensation rate
//  and a coefficient to multiply  alphal for the vaporisation rate

What does this exactly mean?

I tried following the steps within the solver and found that for mDotAlphal, the dimensions of the value pair returned are different from anothe.r mDotAlphal[0] (which is mass condensation) is dimensionless and for mDotAlphal[1], the dimension is [kg/s^2/m]. The same is true for the mDotP().

Now, there is a read() function build into the the class as well. As far as I can see, it is never really called, but when following the code if read() would be called, then some of the coefficients are defined differently (namely they include dimensions instead of no dimensions). So, if this read() is called, then the dimensions for all returned values are [kg/m^3/s].

Does anyone know if read() is called while running interPhaseChangeSolver? And what is supposed to be returned by the functions (dimension wise).

vahid.najafi February 24, 2012 03:08

mDotp() and mDotAlphal()
 
Hello OpenFoam users ,
I'm studying on the Kunz model.we know in this model we have two term for mass dest and prod.(m+ and m-)
What mean mDotAlphal() and mDotP() In interphasechange?
What is the difference between these two?

boger February 28, 2012 09:03

mDotP and mDotAlpha each have to do with the way that the mass transfer terms are linearized in the p-equation and alpha-equation, respectively. The best way to understand each is to write out the equations in which they are used, looking at pEqn.H and alphaEqn.H. Parts of the terms are treated implicitly, and other parts explicitly. Note that pos and neg are effectively the derivatives of the max and min terms, respectively.

vahid.najafi March 1, 2012 20:25

myinterPhaseChangeFoam
 
1 Attachment(s)
Dear David ,
My purpose is adding Zwart and Singhal models to interPhaseChangeFoam solver.
I transform Saur model to Zwart model successfully but transforming Saur model to Singhal model is faild!!!
my error is :

phaseChangeTwoPhaseMixtures/phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixture.C:48: error: no matching function for call to ‘Foam::dimensioned<double>::dimensioned()’

I hope your help to solve this problem.
Thanks a lot.

gaza June 15, 2015 11:44

Hi
pos and neg functions are defined in scalar.H file
they are not derivatives! They return 0 or 1 value :)
Regarding mDotAlphal and mDotP functions they are implemented for cavitation models.
They are inappropriate for heat transfer mass transfer models (condensation, evaporation).
One have to change a bit the code (places where these functions) are used and write own functions as well.


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