Micro particles interaction

  • Last Post 29 November 2019
Alireza766 posted this 12 November 2019

Hi everyone, I want to simulate microparticles between 2 flat plates (2D simulation) and it is crucial for me to know the effect of every particle to the other particles. Because the particles are in Micro it is important for me to consider Brownian motion in my simulation. As I found I ANSYS can do this simulation for me but I don't know which module of ANSYS I should use. I want a guide on how to set up the multiphase parameters. I would appreciate your response. 

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Alireza766 posted this 13 November 2019

Thanks for your reply. 

I am not working on diffusion. I have slurry fluid which contains carbon particles. The behaviors of carbon particles and their interaction is important for me.

rwoolhou posted this 13 November 2019

Read up on the DDPM and Eulerian multiphase models. Also work through the physics you're trying to model: you need to understand what forces/interactions matter, and what they do. Then apply the correct models. 

Alireza766 posted this 13 November 2019

Thank you very much for your helpful advice. Could you please send me your mentioned file or note me that where can I find them?

rwoolhou posted this 14 November 2019

Click on "Help" in Fluent, and navigate to the guides. This bypasses a password system so I can't send you a link as you won't have access. 

Alireza766 posted this 18 November 2019

thanks a lot. I read them up but I have a question, As I explained I have a charged carbon particles that are flown in the slurry fluid(Dense fluid) which are on the Microscale. Fluent can simulate their behavior or I should make it couple with Rocky? I found that Rocky is a good option for particle tracking but I don't know is good for microparticles(Brownian motion) or not. As you know when we have charged particle the mechanical forces are not merely the effective forces between particles and there are electromagnetics forces.

Furthermore, I found that DDPM cannot consider Brownian motion(11.6. Particle Tracking Within the Eulerian Multiphase Framework).

rwoolhou posted this 19 November 2019

Work out what you're trying to model. Ie are particle interactions common? So far you're wanting Brownian motion in slurry flow: given a slurry is high volume fraction how does it effect the flow/motion of particles? 

Alireza766 posted this 19 November 2019

As I found there are 2 ways for particle tracking, 1- Discrete phase(DEM&DEM), 2- Multiphase flow. 

A discrete phase is a good option for fluid in which volume fraction is less than 10% and the DPM method cannot simulate Brownian motion but I think by setting Cunningham Correction it is possible to consider Brownian motion in DEM. 

The second method is using the mixture model and Eulearion model which I am reading about them and I think for a dense fluid(Slurry) the best option is Eulerian model(maybe)!

In slurry, I have carbon particles and it is crucial to know about particle to particle and particle to fluid interactions. The charged carbon particles will be injected between 2D flat plates from inlet and exit from the outlet by a constant flow velocity

rwoolhou posted this 20 November 2019

Pretty much: we use Eulerian models for most slurry systems or cheat and assume it'll flow based on nonNewtonian viscosity. 

Now, how much effect will Brownian motion have on the particle flow when you also account for all the other forces? 

Alireza766 posted this 21 November 2019

The fluent Theory guide is very confusing. In Section Limitation on the Particle Volume Fraction'' The discrete phase formulation used by ANSYS Fluent contains the assumption that the second phase is sufficiently dilute that particle-particle interactions and the effects of the particle volume fraction on the gas phase are negligible.'' In 16.15. Discrete Element Method Collision Model ''ANSYS Fluent allows you to use the discrete element method (DEM) as part of the DPM capability.'' If DEM behaves like DPM, it cannot follow the particles! But in DEM mentioned it can.

In other sections ( Brownian Motion Effects) mentioned that we can add Brownian motion to Discrete Phase simulation but in another place (ANSYS Fluent 19.2 beta features_13.6.1. Limitations) ''The following forces are not supported: Forces arising in rotating frames of reference, Thermophoretic force , Brownian motion''!

Could you please help me with it. I can use DEM or not? The concentration of carbon particles in the slurry is less than 10%. Could you please advise me where can I find a tutorial about using the DEM method for only 2 particles in the channel(For my first approach).


rwoolhou posted this 22 November 2019

How big are the particles relative to the channel? 

Alireza766 posted this 24 November 2019

The particles are from 10^-6 to 10^-7 and they are flown in the 150*50 micrometer and the length of the channel is 10mm.

Alireza766 posted this 25 November 2019

I need a tutorial for DPM(DEM) simulation, there are tutorials for mixture model and VOF but there is no file for DPM, could you please help me where can I find a step by step tutorial for DPM simulation?

As I've found for DPM and DEM simulation I should use coupling software like Rocky DEM or workbench Fluent can simulate it exclusively?


rwoolhou posted this 29 November 2019

I don't think we have a DEM tutorial at the moment, not on the public system anyway.