[johnwinter]

Hi Amir/Flanker,

I have question regarding usage of Brownian force in Turbulent flow. It was mentioned in the Fluent 6.3.26 manual (section 22.2.1) that "Brownian force is intended only for nonturbulent models". is it??

I have already tested Lagrangian model (Fluent in built) for very fine particles such as 1nm and 5 nm. No. of particles deposited is almost same in both cases. Could please give me some suggestion how i can improve my results.

Thanks
John

[Amir]

Originally Posted by johnwinter

Hi Amir/Flanker,

I have question regarding usage of Brownian force in Turbulent flow. It was mentioned in the Fluent 6.3.26 manual (section 22.2.1) that "Brownian force is intended only for nonturbulent models". is it??

I have already tested Lagrangian model (Fluent in built) for very fine particles such as 1nm and 5 nm. No. of particles deposited is almost same in both cases. Could please give me some suggestion how i can improve my results.

Thanks
John

Dear John,

About brownian motion in turbulent flow, I think manual statement makes sense because it can be ignored in comparison with turbulent dispersion mechanism but I didn't check that before.
And about deposition issues; I saw number of papers in which this issue was reported and 2 UDFs were written for both brownian motion and deposition; it's stated that there is a problem in particle velocity interpolation near boundaries which affects deposition; but as a general recommendation, it's better to use eulerian model for such range of diameters to get rid of such problems.

Bests,

[johnwinter]

Hi Amir,

Thanks for your reply. Could you please name the papers who used UDF for Brownian motion in DPM model.
As you suggested i am planning to go for Eulerian method.

Thanks
John

[Amir]

Originally Posted by johnwinter

Hi Amir,

Thanks for your reply. Could you please name the papers who used UDF for Brownian motion in DPM model.
As you suggested i am planning to go for Eulerian method.

Thanks
John

Dear John,

Effectiveness of Direct Lagrangian Tracking Models for Simulating Nanoparticle Deposition in the Upper Airways; P. Worth Longest and Jinxiang Xi, Aerosol Science and Technology, 41:380–397, 2007

This is the most famous paper of this group, you can also find other papers of these authors in this field.

Bests,

[mazdak]

hi.
as you know, in DPM of Fluent, 0.3 *(K/epsilon) is used as eddy life time.
is it possible to write a udf to use another formula for eddy life time instead of
above equation? and if yes how?

[m003020002]

Hi experts,
I would like to add the transport equation of source term(Temperature) into the UDS for fluent and how can I do ?

My geometry is a 3D cubical and it's enclosure, the fluid is water+nanofluid(Al2O3).

I want to observe the natural convection heat transfer phenomena of nanofluids
likes Rayleigh and number Nusselt number.

Do I need to supply more details ?

please help me