buoyancy force: Model 'A' and 'B'

Submitted by naukkarinen on Wed, 09/10/2014 - 11:12

Hei,

I am modelling resin beads (< 1 mm) in a small flow channel. Density ration (rho_f/rho_s) is someting 10^(-1) so buoyancy force can not be neglated. As you know; In the Model 'A', pressure forces includes buoyance force; and In the Model 'B' the buoyancy force have to add separately. I read the cfdemSolverPiso.C to figure out how the hydrostatic (pressure due to altitude difference) pressure is implemented. I found out it is not implemented, am i right? The second question, Is it realistic to use 'Archimedes' force with Model 'A' if hydrostatic pressure is not implemented?

Best regards,
Tomi Naukkarinen

Forums:

cgoniva's picture

cgoniva | Mon, 09/15/2014 - 08:49

Hi Tomi,

You are right, hydrostatic pressure will not be pictured by cfdemSolverPiso. Yes, you can include the effect of buoyancy via the Archimedes force then.

Cheers,
Christoph Goniva

Detian Liu | Sun, 05/03/2015 - 02:11

Dear Christoph,

What do you mean by hydrostatic pressure will not be pictured by cfdemSolverPiso? Is that means if we use the cfdemSolverPiso, we should add the buoyancy force, and then what is the pressure force for? Just for the effect of dynamic pressure on the particles? and it seems that, if we use the Archimedes force in model A, it will not reflect to the CFD side? Is this right or not?
Thank you so much!

Detian
2015.5.2

naukkarinen | Tue, 08/18/2015 - 14:01

Hey Detian,

"What do you mean by hydrostatic pressure will not be pictured by cfdemSolverPiso? Yes
"Is that means if we use the cfdemSolverPiso, we should add the buoyancy force," depend on case
"and it seems that, if we use the Archimedes force in model A, it will not reflect to the CFD side?" Yes, but you can adjust it

Naukkarinen

shawnwuch | Sat, 11/14/2015 - 17:06

Please educate me on the three questions that I have:

1. For a correct buoyancy implementation for a slurry flow (e.g. water + ceramics (SG=1.2) ) in cfdemSolverPiso, should I use, for example, model "A" + "gradPForce" + "Archimedes" or"Bfull" plus "Archimedes" ?

2. With the above setting, do I need to modify any code (either on the CFDEM of DEM side) to correctly apply the buoyant force? And under what situation could I get away with a close answer without any modification?

3. Among viscous, gradP, and drag forces, is drag the only force that is currently accounted for in the particle-fluid momentum exchange term?

Your help is sincerely appreciated.

naukkarinen | Mon, 09/15/2014 - 14:45

I was a quite sure about Archimedes force after some discussion with my colleague . . . but thx :)