[masoud.ravan]

Originally Posted by furqanrk

Have you implemented PBM model with command
> /define/models/addon-module ?
If Yes... There is manual in fluent, very easy and useful !

Good Luck

Thanks for respond,

Actually no, I didn't use PBM yet. I want to learn the concept of this model
I appreciate if anyone knows a reference.

[sepehrkhn]

Hi
I am modeling two phase(water-in-oil) multiphase in a tank with Rushton impeller and I face a problem in aggregation and breakage system of my PBM. the problem is that I use discrete method for population balance and I have 7 bins. the bin fractions are not correct. (bin0=.99 and other bins are totally 0.01) I should mention that bin0 is the bin with largest droplet diameter. it seems that breakage doesn't happen in my tank. even I just use breakage without coalescence I saw no change in droplet diameter.
any help will be appreciated

[BlnPhoenix]

Originally Posted by sepehrkhn

Hi
I am modeling two phase(water-in-oil) multiphase in a tank with Rushton impeller and I face a problem in aggregation and breakage system of my PBM. the problem is that I use discrete method for population balance and I have 7 bins. the bin fractions are not correct. (bin0=.99 and other bins are totally 0.01) I should mention that bin0 is the bin with largest droplet diameter. it seems that breakage doesn't happen in my tank. even I just use breakage without coalescence I saw no change in droplet diameter.
any help will be appreciated

Which Kernels are you using for water-in-oil breakup and coalescence?

[sepehrkhn]

Originally Posted by BlnPhoenix

Which Kernels are you using for water-in-oil breakup and coalescence?

I use Luo model for both with surface tension of 0.02

[furqanrk]

Originally Posted by sepehrkhn

Hi
I am modeling two phase(water-in-oil) multiphase in a tank with Rushton impeller and I face a problem in aggregation and breakage system of my PBM. the problem is that I use discrete method for population balance and I have 7 bins. the bin fractions are not correct. (bin0=.99 and other bins are totally 0.01) I should mention that bin0 is the bin with largest droplet diameter. it seems that breakage doesn't happen in my tank. even I just use breakage without coalescence I saw no change in droplet diameter.
any help will be appreciated

Can you try to use 'LOG NORMAL' values to set your bins value from velocity boundary condition window ?

[sepehrkhn]

Originally Posted by furqanrk

Can you try to use 'LOG NORMAL' values to set your bins value from velocity boundary condition window ?

I dont have inlet. I just patch a volume of the tank as a secondary phase ant start calculation after. but after the bin0 fraction which is the largest bin starts increasing to 0.99 .

[furqanrk]

Originally Posted by sepehrkhn

Hi
I am modeling two phase(water-in-oil) multiphase in a tank with Rushton impeller and I face a problem in aggregation and breakage system of my PBM. the problem is that I use discrete method for population balance and I have 7 bins. the bin fractions are not correct. (bin0=.99 and other bins are totally 0.01) I should mention that bin0 is the bin with largest droplet diameter. it seems that breakage doesn't happen in my tank. even I just use breakage without coalescence I saw no change in droplet diameter.
any help will be appreciated

How did you set Bins fraction in fluent ? How do you know that one bin should 0.99 and other total is 0.01 to make it equal to 1. Do you have any experimental data ? Or do you have Mean you particle size ? Let assume mean particle size is 0.25 cm and your desire to solve it around 7 bins. so, my suggestion is :

Bins 7
Ratio 1.3
Let asume Min size 0.1 cm ( better to use experimental value )
then set like this:
Fraction
Bin-0 0
Bin-1 0
Bin-2 0
Bin-3 1 ( The mean particle size 0.25cm will the middle one )
Bin-4 0
Bin-5 0
Bin-6 0

Good Luck

[sepehrkhn]

Originally Posted by furqanrk

How did you set Bins fraction in fluent ? How do you know that one bin should 0.99 and other total is 0.01 to make it equal to 1. Do you have any experimental data ? Or do you have Mean you particle size ? Let assume mean particle size is 0.25 cm and your desire to solve it around 7 bins. so, my suggestion is :

Bins 7
Ratio 1.3
Let asume Min size 0.1 cm ( better to use experimental value )
then set like this:
Fraction
Bin-0 0
Bin-1 0
Bin-2 0
Bin-3 1 ( The mean particle size 0.25cm will the middle one )
Bin-4 0
Bin-5 0
Bin-6 0

Good Luck

thank dude, I model experimental data from another guy... the particle size varies between 50micrometer to 280 micrometer so I use this size in population balance and ratio equal to one.
I patch the volume fraction and I patch bin fractions as follows:
bin0,1,3,4,5,6=0.1
bin2=0.4 because the sauter mean diameter is in this range.

[Mojtaba_]

hello everyone
do any one explain the formation of crystal step by step?
secondary phase is my crystal phase and i put the volume fraction zero in boundary condition.
i dont have any computation for secondary phase so this mean that crystal phase is not formatting.
why crystal phase dont form??
could you please help me?

[masoud.ravan]

Hey guys,
Do you know how we could specify size distribution for PBM model by using a file in ANSYS FLUENT?
Thanks in Advance,

[sina_mech]

Originally Posted by masoud.ravan

Hey guys,
Do you know how we could specify size distribution for PBM model by using a file in ANSYS FLUENT?
Thanks in Advance,

Population Balance Model > Definition > File > Load File

You need to assign the number of bins before loading the file. The diameters should be ascending, and only one diameter per line! This is the content of a sample file that I used while ago:

0.0000015
0.000005
0.000029
0.000075
0.000175
0.000375
0.000750

Having the diameters, you can initialize volume fraction of each at inlet/domain.

[masoud.ravan]

Hi everyone
I'm simulating a rectangular duct with velocity inlet and pressure outlet in order to see how water and air (that had been injected from an inlet with each other) separate from each other. I have used the discrete method with 8 bin fractions for solving the population balance equation.
Now I wanna change my method to inhomogeneous and continue the simulation. After adding another phase and defining bin fractions in the third phase, I encounter an error:
================================================== ============================

Node 0: Process 568: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 1: Process 4360: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 2: Process 1952: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 3: Process 3732: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 4: Process 4904: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 5: Process 1448: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 6: Process 3892: Received signal SIGSEGV.

================================================== ============================
MPI Application rank 0 exited before MPI_Finalize() with status 2
The fl process could not be started.

I would be absolutely grateful for your responses...

[masoud.ravan]

Originally Posted by masoud.ravan

Hi everyone
I'm simulating a rectangular duct with velocity inlet and pressure outlet in order to see how water and air (that had been injected from an inlet with each other) separate from each other. I have used the discrete method with 8 bin fractions for solving the population balance equation.
Now I wanna change my method to inhomogeneous and continue the simulation. After adding another phase and defining bin fractions in the third phase, I encounter an error:
================================================== ============================

Node 0: Process 568: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 1: Process 4360: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 2: Process 1952: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 3: Process 3732: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 4: Process 4904: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 5: Process 1448: Received signal SIGSEGV.

================================================== ============================

================================================== ============================

Node 6: Process 3892: Received signal SIGSEGV.

================================================== ============================
MPI Application rank 0 exited before MPI_Finalize() with status 2
The fl process could not be started.

I would be absolutely grateful for your responses...

And I also encountered another problem with the Inhomogeneous method of PBM in AnsysFLUENT.
Do we need special treatment other than enabling aggregation phenomena to make bubbles in a smaller velocity group to go to a bigger velocity group??
I cannot see a transition between velocity groups in my simulations. For instance, when I inject a swarm of bubbles, their diameter would increase till reaching the maximum diameter of their own velocity group and do not go to a bigger velocity group although I have some bigger velocity groups in my problem.
Does anyone have some advice...?
Thanks in advance

[masoud.ravan]

Hello All!
I am using the Inhomogeneous discrete method in AnsysFluent PBM model. I have two phases and I want to define just one bin for each phase...after setting this condition, phrase "-1.#IND" will be showed in Ratio Exponent and Max Diameter box (as shown in the picture)
Do you know what it means...and is it an error??

Thanks in Advance...

[sam_cfdd]

Originally Posted by chittipo

Dear Members,

If you have any specific questions on PBM implementation please post here. I will try to answer them, as I gained some experience in it.

on
- Existing module (or)
- Implementation through UDF

Hi Dear,

Actually I want to find aggregation kernel using experimental data to link with FLUENT but I am not sure how to do this. Can you please help me in this case. I appreciate your assist. Regards.

[sam_cfdd]

Originally Posted by masoud.ravan

Thanks for respond,

Actually no, I didn't use PBM yet. I want to learn the concept of this model
I appreciate if anyone knows a reference.

Hi,

PBM is actually Bullshit and headache but it used alot in industry. If you want I have pdf books and ANSYS documents I can share with you. email me on e.zhaleh@gmail.com.

[masoud.ravan]

Originally Posted by sam_cfdd

Hi Dear,

Actually I want to find aggregation kernel using experimental data to link with FLUENT but I am not sure how to do this. Can you please help me in this case. I appreciate your assist. Regards.

Hi
Do you mean that you wanna develeop a kernel? Like lou and other researchers?
Please explain more...

[sam_cfdd]

Originally Posted by masoud.ravan

Hi
Do you mean that you wanna develeop a kernel? Like lou and other researchers?
Please explain more...

Yes, exactly. I wanna develop my kernel. I read lots of article such as luo and others but I couldn't undrestand what did they do.

[masoud.ravan]

Originally Posted by sam_cfdd

Yes, exactly. I wanna develop my kernel. I read lots of article such as Luo and others but I couldn't understand what did they do.

They either performed an experimental investigation or used other's experimental data to validate their kernels. If you want to develop a kernel for coalescence or break-up, you have to perform or choose an air-water experiment like bubble injection from recent works and simulate it, and the last step is evaluation the agreement between the numerical and experimental data.

Good Luck,
Masoud Ravan

[seinfeld2]

Hi all,

I'm trying to simulate CO2 bubble cavitation in water with dissolved CO2 flowing in a venturi tube. Is using this model in the right direction? If anyone can guide me through just a starting point with using this model, that'd be great. What should the From and To Phase be under mass transfer? Is using species appropriate?

Regards.