[cg2308]

Hi all,

I am attempting to model particle fluidisation using the multiphase model. I have been able to model the particles with a uniform diameter, however now I would like to apply a particle size distribution so my diameters become polydisperse. For context, my model is simulating drug particles in an inhaler device. I have the PSD in graphical form and in table form of diameters and % distribution (but no equation - I can get an approximation but it is not very accurate).

I am unsure of the best way to proceed with this. I have read about simply adding more phases for each diameter which would involve simplification of the PSD. I have also looked at developing a UDF but have no experience with C language so this takes some time for me to understand. From looking at previous forum posts, I have been unable to find a solution using UDF's even though similar questions to mine have been asked. This leads me to wonder if it is possible to develop a UDF for polydisperse diameters in a multiphase model?

So I am asking - what would be the best method for me to proceed with for modelling polydisperse diameters in my multiphase flow? Thankyou muchly

[vinerm]

It depends upon the current model that you are using. Is it PBM or Eulerian or Mixture or DPM?

[cg2308]

Hi Vinerm, I am using mixture model

[vinerm]

The simplest method in your case would certainly be to proceed with multiple secondary phases since the distribution you have is discrete. UDF can be used and you can certainly expect help from the Forum, however, you need to have a pseudo-code ready about how you want to proceed. On what basis do you want to provide diameter values back to Fluent? At any given time, only one value is returned.

[cg2308]

Ok thankyou for the helpful response, I very much appreciate it!

For my case, I have a cavity which I initially fill with the particles. I then track the particles leaving the cavity after they fluidise - I don’t have any further injections etc. So from what you have said, if only one diameter can be returned at a time, I don’t think a UDF will be appropriate for my case as I only input the diameters once before I begin the simulations?

[vinerm]

Returning one value at a time does not put a constraint on the number of diameters. You can have as many different values you want as long as the reason for variation is known. E.g., if diameter has to change on the basis of shear rate, then a new diameter would be calculated and returned to Fluent.

[cg2308]

Right ok, well I would like my diameters to be assigned via the particle size distribution, eg 15% 50 micron, 5% 100 micron etc. I think I have thought of how the code might work, so I will write it out and test it. Thankyou for your help

[vinerm]

That's good that you have an idea about how to implement it.