[dhiraj.lote@gmail.com]

Originally Posted by Jann U

Hello everybody!


In the Users Guide it is stated that the DEFINE macros of the Population Balance model are executed at the beginning of every time step.


1. Does that mean that the Population Balance Model or at least the UDFs are not suitable for steady state?


2. I'd also love to know whether the PBE is calculated along the transport equations or at a different location in the algorithm?


Any help would be much appreciated!

Hello,
1. Ofcource PBM or UDFs are very important and suitable for steady state simulations. The meaning you need to understand for steady and unsteady state simulation is that, in unsteady simulations we are interested in intermediate results (depends on time steps) while in steady state simulations we are completely avoiding the intermediate solutions and are only interested in final solution. so PBM and UDFs are very suitable in steady state.
2. PBE gives the idea about the total number balance of the bubbles/droplets/particles. Total number balance means it always balances the volume of the dispersed/secondary phase. So PBE is getting solved seperatly along with the Continuity and Momentum equation.

[Jann U]

Originally Posted by Jann U

Hi!


I started experimenting with UDFs for the PBM and immediately ran into problems:


I compiled the following UDF (no error was thrown)




DEFINE_PB_NUCLEATION_RATE(nucrate, cell, thread){

real J = 1.0e7;

return J;
}


However when I select the UDF for the nucleation rate in the PBM dialogue box and press Apply the UDF is deselected and simply the previous constant value is displayed.


Has anybody experienced anything similar?


Any help would be much appreciated?

I solved the issue by activating the eulerian model instead of the mixture model. In case anybody runs into the same problem.


Cheers.

[cultivate]

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

I'm having trouble writing the luo breakup model.I would appreciate if you helped me.Thanks again

[Triskelion]

Hi chittipo.
I have some questions about Fluent by using DQMOM in a eulerian-eulerian approach.
(1) My simulation is a gas-solid flow, solid phase is the secondary phase and only one material. But in DQMOM, I have to input three secondary phases. Do I have to create three phases with the same characteristics? When I define where the granular phase is, which phase do I use ? (2) How can I initialize for using DQMOM? I have already patched the solid volume fraction, and I output the solid-property-diameter, but I cannot get my correct mean diameter, so what else do I need to do? I cannot figure out the meaning of QDMOM-m4-0 in the initialization.
These have been bothering me for a long time. Thank you very much!!!

[masoomabilal]

dear members,
I am working with ansys fluent package 2020 R2. I have to determine the particle size distribution of microcapsules of PEI and PVA. process is taking place at 5000 rpm and hence it's a steady state system. despite putting my effort into changing parameters, I am facing a divergence detected in the AMG solver in some settings all the parameters are diverging while in some settings only epsilon is diverging. I have tried every possible way of doing this can anybody help me in this respect, please?
I am using the discrete method of population balance modelling eulerian approach and standard k-epsilon turbulence models. enabled surface tension force wall adhesion, mass transfer through population balance mechanism, ia. particle for the interactive force, schiller nauman drag force, sato turbulent interaction between dispersed and continuous phase, surface tension along with the nucelation, growth, aggregation and breakage for aggregation turbulnet model selected while for breakage luo models. even when i run the program with default settings it diverges and then say epsilon is negetive in few cells
please help if an body can
i shall be extremely thankful tou
regards,
masooma