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InterPhaseChangeFoam: trying to simulate cavitation phenomena inside of nozzle

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Old   January 20, 2014, 02:53
Default InterPhaseChangeFoam: trying to simulate cavitation phenomena inside of nozzle
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Baris (Heewa)
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Dear Foam Users,

I am trying to simulate cavitation phenomena inside of nozzle and using interphasechangefoam. As you know that there are 3 transport models (Merkle, Kunz and Sauer) I have tried all of these 3 models with kwSST turbulence model however i have problems with the obtaining of cavitation region as follows;

1. If i set the initial cond. according to Velocity as follows:
==> 0/U
Code:
internalField   uniform (0 3.104 0);
boundaryField
{
    inlet
    {
        type            fixedValue;
        value           $internalField;
    }
      outlet
    {
        type            pressureInletOutletVelocity;
        phi             phi;
        value           $internalField;
    }
    wall
    {
        type            fixedValue;
        value            uniform (0 0 0);
    }
==>0/P
Code:
internalField   uniform 1e5;
boundaryField
{
   inlet
    {
         type           zeroGradient;
    }
    outlet
    {
        type            fixedValue;
         value           $internalField;
    }
    wall
    {
        type           zeroGradient;
    }
}
cavitation starts to form until to some level, however after that it disappears although flow rate is increasing. I didnt understand why this happens? (as seen in the attached fig.)

2.if i set the initial cond. according to pressure as follows:
==>0/P
Code:
internalField   uniform 1e5;
boundaryField
{
    inlet
     {
        type            fixedValue;
        value           uniform 2.8e5;
    }
    outlet
    {
        type            fixedValue;
         value           $internalField;
    }
   wall
    {
        type           zeroGradient;
    }
==>0/U
Code:
internalField   uniform (0 0 0);
boundaryField
{
    inlet
    {
        type            zeroGradient;
        value           uniform (0 0 0);
    }
    outlet
     {
        type            inletOutlet;
        inletValue       uniform (0 0 0);
    value         uniform (0 0 0);
    }
    wall
    {
        type            fixedValue;
        value            uniform (0 0 0);
    }
in this case no cavitation form obtained. Therefore i am confused. Could someone advice me something or give some insight what kind of reasons can result in these results? I increased mesh number, changed mass transport model( means i tried 3 of models) still gives same results...

In addition; For interphasechange solver (or more generally if we try simulation multiphase with mass transition which initial condition setting is more logical; pressure or velocity based?

Thanks in advance...
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Old   January 20, 2014, 02:55
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Baris (Heewa)
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Sorry I forgat to say that initial velocity and pressure values are taken from the experiment...
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Old   April 23, 2015, 08:46
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Alexander Bartel
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Hi Baris,

are you still working on that issue?

regards
Alex
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Old   April 23, 2015, 15:42
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Hi Alex,

Yes I am still working about same topic.

Do you have any question?

B
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Old   April 24, 2015, 09:51
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Alexander Bartel
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I didn't realize, that you are sure pretty experienced, so I assume that you aren't stuck at the same place like one year before...

I think i wanted to help you yeserday.

I currently try different things with InterPhaseChangeDyMFoam, but my problem is more a lack of c++ knowledge... thanks for your offered help and sorry for the unnecessary disturbance.

regards
Alex
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Old   April 24, 2015, 10:45
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Baris (Heewa)
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Thank you for your kind consideration. Yes, i faced stability problem for a long time. However, finally i fixed and solved the problem.

I think that C++ is main problem for all new beginners. This can be also fixed in time with hard work

Please keep in touch and let me know about your challenge and brief findings in InterPhaseChangeDyMFoam.

BR

Baris
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Old   May 19, 2015, 07:09
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Hi people,
I have seen you are using interPhaseChangeFoam to simulate cavitation phenomena inside nozzle. Actually I'm working in this topic too. I have a question about this solver I hope you could answer me: interPhaseChangeFoam works with a hydrostatic pressure definition, isn't it? Did you do your simulations with this pressure definition or did you do any change?
And... to make this change, is it necessary to modify the pEqn.H file, or is there another easy way?
Regards,
Alvaro.
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Old   May 19, 2015, 17:32
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Alexander Bartel
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Hi Alvaro,

did you try to work with the cavitatingBullet tutorial multiphase/InterPhaseChangeFoam/cavitatingBullet ?
You can change the geometry and customize it for your case.

regards
Alex
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Old   May 19, 2015, 21:45
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Baris (Heewa)
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Hi Alvora,

Here hydrostatic pressure definition is just a kind of trick to simplify the boundary conditions and also increase the stability when the gravity should be considered. I just didnt understand why you want to change it? Finally, solver also calculate the total pressure as calculated and indicated in "CreateFields.H" P=p_rgh+rho*gh. As Alex said you can look at cavitatingBullet tutorial or last year i attended to CFD open course in Chalmers and already written a tutorial which explains cavitatingFoam and interPhaseChangeFoam for nozzle cavitation. You can also download and check it here: https://www.researchgate.net/publica...njector_Nozzle

BR.

Baris
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Old   May 20, 2015, 07:42
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Hi,

I've seen your work Baris, and looks fine. I've tried to implement the code but I have a problem in the step to compile "phaseChangeTwoPhaseMixtures". The terminal returns me the following error and I don't know how to solve it.
Code:
alvaro@AlvaroPC:~/OpenFOAM/alvaro-2.3.0/applications/solvers/multiphase/TransportCavitatingFoam/phaseChangeTwoPhaseMixtures$ wmake
linux64GccDPOpt/options:5: *** missing separator.  Stop.
wmake error: file 'Make/linux64GccDPOpt/objectFiles' could not be created in /home/alvaro/OpenFOAM/alvaro-2.3.0/applications/solvers/multiphase/TransportCavitatingFoam/phaseChangeTwoPhaseMixtures
alvaro@AlvaroPC:~/OpenFOAM/alvaro-2.3.0/applications/solvers/multiphase/TransportCavitatingFoam/phaseChangeTwoPhaseMixtures$
I have to warn you that I have no knowledge of C++ programming. This are the Make files.
Make/files
Code:
phaseChangeTwoPhaseMixture/phaseChangeTwoPhaseMixture.C
phaseChangeTwoPhaseMixture/newPhaseChangeTwoPhaseMixture.C
Kunz/Kunz.C

LIB = $(FOAM_USER_LIBBIN)/libphaseChangeTwoPhaseMixtures
Make/options
Code:
Kunz/Kunz.C

LIB_LIBS = \
    -L$(FOAM_USER_LIBBIN)

EXE_INC = \
    -I$(LIB_SRC)/transportModels/twoPhaseMixture/lnInclude \
    -I$(LIB_SRC)/transportModels \
    -I$(LIB_SRC)/transportModels/incompressible/lnInclude \
    -I$(LIB_SRC)/finiteVolume/lnInclude

LIB_LIBS = \
    -ltwoPhaseMixture \
    -ltwoPhaseProperties \
    -lincompressibleTransportModels \
    -lfiniteVolume
And the file options generated in the folder linux64GccDPOpt.

Code:
# 1 "options"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "options"
Kunz/Kunz.C

LIB_LIBS = -L$(FOAM_USER_LIBBIN)


EXE_INC = -I$(LIB_SRC)/transportModels/twoPhaseMixture/lnInclude -I$(LIB_SRC)/transportModels -I$(LIB_SRC)/transportModels/incompressible/lnInclude -I$(LIB_SRC)/finiteVolume/lnInclude
Could you help me to compile the case correctly?
Thanks.
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Old   May 21, 2015, 04:13
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Hi again,
I ran the simulation with interPhaseChangeFoam and I obtained high negative pressure values. I think it's wrong, but why does this happen? How can I avoid that?
Regards
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Old   May 21, 2015, 06:04
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Hi alvaro,

negativ pressure values aren't bad if they don't exceed -1e+05 Pa (-1bar) . I never gave it a thought, because I think its effective pressure and not absolute pressure plotted by paraView.

regards
Alex
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Old   July 16, 2015, 04:43
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I think I have to correct myself.
I read in some posts, that p is the absolute pressure in InterPhaseChangeFoam, so you have discovered really an error.

Edit:
Now I have to correct/clarify my correction.
My first suggestion
Quote:
negativ pressure values aren't bad if they don't exceed -1e+05 Pa (-1bar) . I never gave it a thought, because I think its effective pressure and not absolute pressure plotted by paraView.
is not wrong, but confusing, because my second statement
Quote:
p is the absolute pressure in InterPhaseChangeFoam
is also right.

As read here: InterPhaseChangeFoam ERROR
Quote:
Originally Posted by pEqn.H
p == p_rgh + rho*gh;
p is the absolute pressure
p_rgh is the relative/effective pressure that is plotted by paraFoam
rho*gh is the atmospheric pressure

so everything is fine in my computation.

regards
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Last edited by alexB; July 16, 2015 at 07:09.
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Old   December 14, 2015, 08:27
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Hello Alex,

I'm not completely sure that you are right.You can find something about the negative pressure issue in this tutorial:http://www.tfd.chalmers.se/~hani/kur...lenceModel.pdf
page 16


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Old   December 14, 2015, 20:10
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Baris (Heewa)
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Hi Jiri,

In that tutorial he also said that negative pressure is unrealistic condition.

Quote:
. To prevent
from this unrealistic condition, one option is using a very high value for evaporation coefficient
Frankly speaking, according to my experience, absolute pressure can not be negative. However, somehow for a small duration a local pressure around bubbles can be measured negative in some experiments. This is definitely unrealistic conditions. (Because absolute pressure min can be 0 under the lab condition. look at the definition here: https://en.wikipedia.org/wiki/Pressu...nization_gauge) Therefore, if you have so small negative calculated value then you can ignore it.

BR

Baris
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Old   December 15, 2015, 07:58
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Quote:
Originally Posted by shipman View Post
Hi Jiri,

In that tutorial he also said that negative pressure is unrealistic condition.



Frankly speaking, according to my experience, absolute pressure can not be negative. However, somehow for a small duration a local pressure around bubbles can be measured negative in some experiments. This is definitely unrealistic conditions. (Because absolute pressure min can be 0 under the lab condition. look at the definition here: https://en.wikipedia.org/wiki/Pressu...nization_gauge) Therefore, if you have so small negative calculated value then you can ignore it.

BR

Baris
Hello,

Yes, I agree with this statemt. It was reaction to the last post. I have to confess that I read the thread only cursorily. On the other hand I thought that the tutorial could be useful. Have a nice day!

Regards,
Jiř
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