[sega]

Hello.

Now I'm getting to my next problem:
The rise of sperical bubble to it's terminal velocity.

I used the test-setup described in http://test.interface.free.fr/Case01.pdf

Unfortunately there is nothing about the boundary conditions in this case.
As the boundary should not have an influence on the shape and even on the terminal veloctiy (if the computational domain is large enought), i chosed the following:

left: symmetryPlane for all values (U,pd,gamma) (I use an axisymmetric description
top: totalPressure (0) for pd, uniform (0 0 0) for U, zeroGradient for gamma
left & bottom: zeroGradient for pd and gamma, uniform (0 0 0) for U

To initialize the bubble I used funkySetFields to create a gamma-field at the center of the domain. Here is the image:



I used the same function to initialize the pressure inside the bubble to the value defined by sigma/radius:



Transport Properties were taken from the test-case description mentioned above.

Sounds bad, but it's real: the solver is doing nothing:


Exec : interFoam . .
Date : May 20 2008
Time : 15:16:11
Host : M1530
PID : 6392
Root : /home/sega/OpenFOAM/sega-1.4.1/run/rise
Case : .
Nprocs : 1
Create time

Create mesh for time = 0


Reading environmentalProperties
Reading field pd

Reading field gamma

Reading field U

Reading/calculating face flux field phi

Reading transportProperties

Selecting incompressible transport model Newtonian
Selecting incompressible transport model Newtonian
Calculating field g.h

time step continuity errors : sum local = 0, global = 0, cumulative = 0
#0 Foam::error::printStack(Foam:stream&)

So, there must be something wrong.
Any ideas?

My OpenFOAM-case is located here:
http://therealsega.th.funpic.de/openfoam/rise.tar.gz

[sega]

My first setup was really bad.

I have done this now:
- used the complete computational domain (no symmetry)
- boundary-condition:
U: 0 at the bottom, zeroGradient at all other sides
pd: totalPressure 0 at the top, zeroGradient at all other sides
gamma: zeroGradient at all sides

I initialized the bubble as a sphere of defined radius and defined pressure inside.

All other transportProperties were chosen as in the literature mentioned above.

The simulation is running, but is not computing as I have planned.

- The bubble does not reach the "spherical cap sized" shape. It's more "skirted" at the sides.
Is that due to wall effects (actually there is no wall to the sides)?
Maybe I have to increade the computational domain?



The bubble is rising very slowly.
The image from above is after 30s Simulation time.
From the literature the bubble should reach its final shape and terminal velocity round about 0.1 Seconds ...

[18210436486]

Originally Posted by sega

My first setup was really bad.

I have done this now:
- used the complete computational domain (no symmetry)
- boundary-condition:
U: 0 at the bottom, zeroGradient at all other sides
pd: totalPressure 0 at the top, zeroGradient at all other sides
gamma: zeroGradient at all sides

I initialized the bubble as a sphere of defined radius and defined pressure inside.

All other transportProperties were chosen as in the literature mentioned above.

The simulation is running, but is not computing as I have planned.

- The bubble does not reach the "spherical cap sized" shape. It's more "skirted" at the sides.
Is that due to wall effects (actually there is no wall to the sides)?
Maybe I have to increade the computational domain?



The bubble is rising very slowly.
The image from above is after 30s Simulation time.
From the literature the bubble should reach its final shape and terminal velocity round about 0.1 Seconds ...

hi would you please tell me, how to make 2D region for bubble emerged in water using openfoam? I tried using setFeildsDic, but i do not know why it does not make a region...I am confused..it should be quit easy...

[sega]

Ok, of course I have chosen the wrong transportProperties, and size of the initial bubble. Thats why the bubble was rising too slow and getting "out of shape".

So, now that I did a check on all the numbers, there is another problem.

The bubble is starting to disperse at the skirts.



I have read about this phenomena in "Bubbles, Drops and Particles" (Clift, Grace, Weber. 2005)

Do I have to chose an even smaller mesh-size to stop the bubble from further "divergence"?

[sega]

And now for the harder part:

How can I compute the actual rising velocity over time?

[ngj]

Hi Sebastian

It looks nice. I do not know how to calculate the rising velocity. With respect to the dispersing bubble, I would try trial'n'error with a couple of different resolutions and see what happens.

- Niels

[hjasak]

Hello,

Do you know about the PhD Thesis from Henrik Rusche:

Rusche, H: Computational fluid dynamics of dispersed two-phase flows at high phase fractions, Imperial College, University of London 2003.

He has done a bunch of free-rising bubble simulations in 3-D.

Incidentally, how big is your bubble? In 2-D it will only have approx half the curvature of a 3-D bubble, which will cause some break-up.

Enjoy,

Hrv

[sega]

Dear Hrv.

The complete setup is described in http://test.interface.free.fr/Case01.pdf

So, I used a spherical bubble of 0.02m diameter.

An I have just downloaded the PhD from Henrik Rusche. I will have a look into it.

@Niels: I will try some finer meshes later!

Get back to you!

[sega]

I had a look into the PhD Thesis.
It's consistent with the other theoretical works I have read.

What I'm still missing is a way of calculating the rise-velocity.
The OpenFOAM-PostProcessing is still a mystery to me.

[sega]

I have set up a finer mesh by now and the simulation is running.
The error between estimated and calculated liquid phase volume fraction is at 0.9 %.
So I think the mesh is "good" enough.

I have checked the results during the calculation and the bubble seems to be somehow "dented" at the apex.

If you have a closer look at the mesh in this area you can see that it is finer there in an "uneven" way.
I was not aware of this fact.
Is it possible, that the mesh is causing this trouble?

Maybe I should consider creating a more "balanced" mesh in this area concerning the grid spaces.



P.S. With increasing calculation time the bubble is getting more thinner at the center line:



I don't think thats good ...

[sega]

The bubble split up ...



Looks like a smilie to me

[sega]

Now I could performe a full simulation.

The terminal velocity is reached without significant "overshot".

Have a look:
terminalvelocity.pdf

The shape is pretty good, allthought the bubble is still dispersing a little bit.




BUT: First and graves problem:
Compared to the literature the value of my terminal velocity is over 20% too low ...

[sega]

Hello.

I received a question about how I calculated the terminal velocity.

I have used a post-processing tool I got from the university. I don't know in detail where it comes from, but it was really useful:

barycenter.zip

The tool calculates the location of the mass center of the phase gamma=0 at each timestep.

I tun the tool over my case and put the results into a file named 'center'.

barycenter . . >center

Then I picked the times and positions of the masscenter and calculate the displacement over time which is representing the rising velocity.

Greetings. S.

[Hrushi]

Originally Posted by sega

Hello.

I received a question about how I calculated the terminal velocity.

I have used a post-processing tool I got from the university. I don't know in detail where it comes from, but it was really useful:

barycenter.zip

The tool calculates the location of the mass center of the phase gamma=0 at each timestep.

I tun the tool over my case and put the results into a file named 'center'.

barycenter . . >center

Then I picked the times and positions of the masscenter and calculate the displacement over time which is representing the rising velocity.

Greetings. S.

Hi Sebastian,

I am able to simulate drop rise velocity using interFoam solver. Then I ran barycenter utility as posted above successfully.
I am now stuck at how to extract the time and barycenter coordinate (say in .xy format)?
So that I can calculate instantaneous drop rise velocity over a time.

How did you pick the times and position of the masscenter from center file generated using barycenter utility?

Hrushikesh

[sega]

Originally Posted by Hrushi

Hi Sebastian,

I am able to simulate drop rise velocity using interFoam solver. Then I ran barycenter utility as posted above successfully.
I am now stuck at how to extract the time and barycenter coordinate (say in .xy format)?
So that I can calculate instantaneous drop rise velocity over a time.

How did you pick the times and position of the masscenter from center file generated using barycenter utility?

Hrushikesh

Well I used

barycenter > center

to produce an output file "center", deleted everything i didn't want manually and imported the data with MATLAB ...

[A.J.Chaves]

Hello

I am new here in the forum and I have been working with the same case of the bubble rising. I'm using interDyMFoam and an parallel processing to simulate the case. Now I want to calculate the barycenter of the bubble so I can get the velocity in each step of time. I downloaded the barycenter utility, but when I try to install it, an erro message occurs.

ana@ana:~/OpenFOAM/OpenFOAM-2.1.0/applications/utilities/postProcessing/barycenter$ wmake
Making dependency list for source file barycenter.C
could not open file readEnvironmentalProperties.H for source file barycenter.C
SOURCE=barycenter.C ; g++ -m64 -Dlinux64 -DWM_DP -Wall -Wextra -Wno-unused-parameter -Wold-style-cast -Wnon-virtual-dtor -O3 -DNoRepository -ftemplate-depth-100 -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/transportModels -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/transportModels/incompressible/lnInclude -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/transportModels/interfaceProperties/lnInclude -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude -IlnInclude -I. -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/OpenFOAM/lnInclude -I/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/OSspecific/POSIX/lnInclude -fPIC -c $SOURCE -o Make/linux64GccDPOpt/barycenter.o
barycenter.C:49:44: error: readEnvironmentalProperties.H: Arquivo ou diretório não encontrado
In file included from barycenter.C:52:
createFields.H: In function ‘int main(int, char**)’:
createFields.H:92: error: ‘g’ was not declared in this scope
In file included from barycenter.C:55:
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/setInitialDeltaT.H:35: error: ‘CoNum’ was not declared in this scope
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:3: warning: unused variable ‘nOuterCorr’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:6: warning: unused variable ‘nCorr’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:12: warning: unused variable ‘momentumPredictor’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:15: warning: unused variable ‘transonic’
make: ** [Make/linux64GccDPOpt/barycenter.o] Erro 1
ana@ana:~/OpenFOAM/OpenFOAM-2.1.0/applications/utilities/postProcessing/barycenter$

I'm also a new user of the linux system but I guess the erro occurs because I'm using an new version of the OpenFoam (2.1.0) instead the original one that the utility were made for.
If anyone could help me, I would be grateful.

[Hrushi]

Originally Posted by A.J.Chaves

barycenter.C:49:44: error: readEnvironmentalProperties.H: Arquivo ou diretório não encontrado
In file included from barycenter.C:52:
createFields.H: In function ‘int main(int, char**)’:
createFields.H:92: error: ‘g’ was not declared in this scope
In file included from barycenter.C:55:
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/setInitialDeltaT.H:35: error: ‘CoNum’ was not declared in this scope
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:3: warning: unused variable ‘nOuterCorr’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:6: warning: unused variable ‘nCorr’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:12: warning: unused variable ‘momentumPredictor’
/home/ana/OpenFOAM/OpenFOAM-2.1.0/src/finiteVolume/lnInclude/readPISOControls.H:15: warning: unused variable ‘transonic’
make: ** [Make/linux64GccDPOpt/barycenter.o] Erro 1
ana@ana:~/OpenFOAM/OpenFOAM-2.1.0/applications/utilities/postProcessing/barycenter$

I'm also a new user of the linux system but I guess the erro occurs because I'm using an new version of the OpenFoam (2.1.0) instead the original one that the utility were made for.
If anyone could help me, I would be grateful.

Hi Angelo,

Yes, you are right. You need to make some minor changes in that code. I had done it a year back. I will have to look into my old files. If I get it, I will upload it here asap.

[Hrushi]

Hi Angelo & Tayo

Here is the updated version of baryCenter baryCenter-of201.zip utility. I have tested it on OpenFoam-201. You can comapre the each file in zip archive with one that you have to recognise the changes one needs to make it usable in OF201.

Hope it helps.

Regards
Hrushi

[tayo]

Originally Posted by Hrushi

Hi Angelo & Tayo

Here is the updated version of baryCenter baryCenter-of201.zip utility. I have tested it on OpenFoam-201. You can comapre the each file in zip archive with one that you have to recognise the changes one needs to make it usable in OF201.

Hope it helps.

Regards
Hrushi

Thank you Hrushi. The hard job is done; It compiled fine. I simply ran the application after my simulation run time was complete and it printed out the value. Is there a way to extract the data from the barycenter into a file so that I won't have to manually copy the data? Have a nice weekend.

[Hrushi]

Hi,

Here is the updated version of baryCenter (for OF-2.2.1) baryCenter221.zip utility. I have tested it on OpenFOAM-2.2.1.

Enjoy!