# -nano- scale in CFD

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 January 15, 2013, 11:49 -nano- scale in CFD #1 New Member   anonymous Join Date: Jan 2013 Posts: 3 Rep Power: 6 Dear all, I am new in the forum and I would appreciate any help about the acceleration process of iron-oxide nanoparticles caused by a flow of helium gas in a 1 mm diameter tube . We are interested in getting to know the velocity of the nanoparticles at a fixed length (L) accelerated by the continous phase. Sample input data: Tube diameter = 1 mm Inlet velocity of helium gas = 20 m/s Size of iron-oxide nanoparticles (between 10 and 100 nm) inlet mass flow rate of discrete phase = 1mg/min (10.E10 particles aprox.) Can CFD treat the "nano-scale"? Multiphase models implemented in Fluent are going to be used? Which one would be the most suitable?? Any idea about how to do it if possible? Thanks for all in advance.

 January 15, 2013, 15:01 #2 Senior Member   Join Date: Mar 2011 Location: Germany Posts: 431 Rep Power: 13 If the volume fraction of discrete phase is less than 10% then you can use Discrete Phase Model which uses Lagrange-Euler(Langrange Particle tracking) technique but if the volume fraction is greater than 10% than you have to go for Multiphase Model i.e Euler-euler technique.

 January 16, 2013, 05:01 #3 New Member   anonymous Join Date: Jan 2013 Posts: 3 Rep Power: 6 Dear cfd_seeker, First of all, thank you for your reply and your interest. I think your comment is something to do with the proper use of an Euler or Lagrange approach as far as multiphase modelling is concerned. My question or doubt (or darkness in which I am involved) is concerning about if the general multiphase models implemented in FLUENT -can- take into account the interaction forces between the discret & continous phase (or among the different phases) when we are in a -nano- scale instead of -mili/micro- scale. I have read something and it seems to be that in case of -nano- particles, a special phenomenon or motion or force called -Brownian- appeared, but I know -nothing- about this effect neither a special treatment to be done when a -nanoparticles- aree treated. I would need any help to get to know if this application could be treated with a general-purpose soft like FLUENT or the problem is not as easy like it seems?? Thanks for all in advance and I will be waiting for sb to give some idea.

 January 16, 2013, 05:35 Error in Fluent #4 New Member   Harsha Join Date: Sep 2012 Posts: 8 Rep Power: 7 Hello, This is Harsha actually when i am using fluent 2dd when i initialize the problem and give some 30000 iterations the fluent will start iterating but after 5000 iteration it show a error message and stops the process can anybody please reply to how to get rid or the problem i have made

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