# CFD-DEM Simulation - Particle Size compared to mesh cell size

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 February 24, 2016, 12:37 CFD-DEM Simulation - Particle Size compared to mesh cell size #1 Member   Nadish Saini Join Date: Feb 2014 Location: Raleigh, North Carolina Posts: 39 Rep Power: 12 Hello Foamers, I have a conceptual question to which i am not able to find an answer. I am performing ONE-WAY coupled simulation of micron sized particles suspended in a turbulent flow field. The concentration of particles is low enough for me to consider only one-way coupling. i am solving the flow field using LES. The mesh cell size is generally larger than the particle size. However, near the wall, since LES requires DNS type resolution, the mesh cells are smaller than the particle dimensions. My questions: 1. For one-way coupled simulations, is it necessary to have the condition that particles must be smaller than mesh cells? 2. There must be a way to deal with the situation where DEM particles are larger than mesh cells but i could not find any reference article for it. Can someone please guide me with this. Thanks a ton!

 February 24, 2016, 12:40 #2 Senior Member   Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,793 Rep Power: 71 I think your question is more general than an OF problem... Specifically, I think there is no physical meaning in having a computational mesh size smaller than the particle diameter... Do your particles have a relevant inertia?

February 24, 2016, 12:51
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Quote:
 Originally Posted by FMDenaro I think your question is more general than an OF problem... Specifically, I think there is no physical meaning in having a computational mesh size smaller than the particle diameter... Do your particles have a relevant inertia?

I am not sure what you mean when you say:
"there is no physical meaning in having a computational mesh size smaller than the particle diameter".

The particles i am considering have a mean diameter of 200e-6 m. Thus their inertia would be small, no doubt. The smallest cell dimension (near wall) is 12e-6 m for LES simulation.

 February 24, 2016, 13:16 #4 Senior Member   Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,793 Rep Power: 71 If the particle covers the computational cell You cannot solve the fluid equations there

November 1, 2018, 15:12
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Quote:
 Originally Posted by 90nash Hello Foamers, I have a conceptual question to which i am not able to find an answer. I am performing ONE-WAY coupled simulation of micron sized particles suspended in a turbulent flow field. The concentration of particles is low enough for me to consider only one-way coupling. i am solving the flow field using LES. The mesh cell size is generally larger than the particle size. However, near the wall, since LES requires DNS type resolution, the mesh cells are smaller than the particle dimensions. My questions: 1. For one-way coupled simulations, is it necessary to have the condition that particles must be smaller than mesh cells? 2. There must be a way to deal with the situation where DEM particles are larger than mesh cells but i could not find any reference article for it. Can someone please guide me with this. Thanks a ton!
Dear Saini,
I have a problem similar to your problem but for two-way coupled simulation!
I have simulated the CFD step and now I want to run coupled CFD-DEM that DEM particles are larger than some mesh cells especially near wall.

What must I do? Did you find a solution?

Thank you

 November 1, 2018, 20:50 CFD vs PIV #6 New Member   bambang Join Date: Jun 2018 Posts: 10 Rep Power: 8 Hello, I am a newcomer in CFD. I have one question. What the weakness of PIV if compare to the CFD especially in in-cylinder engine flow. Thank you.