[Time4Tea]

Hi,

I am trying to model a situation where very small metal particles (~50 micron diameter) are being transported through a 7mm ID glass tube by Nitrogen gas.

I am using the discrete phase model in FLUENT and trying to figure out which sub-models I should enable to best capture the behavior. From the attempts I have made so far, it seems that the situation I am trying to model is highly dependent on the average axial velocity of the particles, which in turn is highly dependent on the level of roughness of the wall of the tube.

So, I have enabled the rough wall model and particle rotation, and I have also tried to estimate what the friction factor and coefficient of restitution with the walls would be, to try to model the wall interactions as accurately as possible.

However, it seems to me that the turbulence in the tube may also have quite a large effect, as I can imagine the turbulent eddies would be the main factor imparting lateral motion to the particles, which would increase the likelihood of them impacting with the sides of the tube. Without turbulence (i.e. a RANS model), the average gas velocity will be purely axial, which may under-represent the particle collisions with the walls.

So, I know that the FLUENT DPM has two ways to model the effect of turbulent eddies on the particles: stochastic tracking and the cloud model. Does anyone have any experience with either of these models and/or modelling transport of particles through tubes (in FLUENT or other software)? If so, have you found either of these models to be more suitable for this kind of situation? Were you able to achieve results that matched experimental data?

Of course, I could look at doing a DES/LES simulation to model the transient eddies more directly. However, that would probably be a lot more tricky/time-consuming.

[FMDenaro]

LES could be the correct formulation, the computational cost depends on the dimensions of your geometry.
Small particles can have small inertia and therefore they are strongly affected by the turbulence fluctuations, if you use RANS you can just observe the dynamics of the particles due to the averaged velocity.

[Time4Tea]

Ok, thanks for your input, FMDenaro. Yes, it seems that if I want to get a really accurate representation of the behavior of the particles, I would need to look at LES.


Have you had any experience with the FLUENT DPM turbulence models that I mentioned though (stochastic tracking or cloud tracking)? Do you know which of those would be more suitable for this type of scenario (as a next-best alternative to LES)?

[FMDenaro]

Originally Posted by Time4Tea

Ok, thanks for your input, FMDenaro. Yes, it seems that if I want to get a really accurate representation of the behavior of the particles, I would need to look at LES.


Have you had any experience with the FLUENT DPM turbulence models that I mentioned though (stochastic tracking or cloud tracking)? Do you know which of those would be more suitable for this type of scenario (as a next-best alternative to LES)?

No experience about Fluent DPM, sorry. Ask in the dedicated forum.

[Time4Tea]

Ok, will do. Thanks!