CFDEM®coupling - User Forum

Hello All,

Dear all,

Have anyone checked the formula of Di Felice drag force used in CFDEM pavkage?

As I see from the source code (DiFeliceDrag.C) and the refered paper Zhou et al. (2010), the drag coefficient is calculated as:
dragCoefficient=0.125*Cd*rho*M_PI*ds*ds*pow(voidfraction,(2-Xi))*magUr.

However, as I see from Di Felice (1994), the power law coefficient is -Xi while not (2-Xi). In fact, In the literature, there are several variations for the power law coefficient, including 2-Xi (Zhou et al, 2010), -Xi (Felice, 1994), 1-Xi (used in Xu et al, 2000).

Dear CFDEM community,

Has anyone used the smoothing model in CFDEM before? I wonder what's the theory or underlying science for the smoothing approach used in CFDEM?

What I get from the code is that it solves a diffusion equation for the void fraction and the momentum exchange term Ksl.

******************************************************************************
double deltaT = vSmoothField_.mesh().time().deltaTValue();
DT_.value() = smoothingLength_.value() * smoothingLength_.value() / deltaT;

Hi,

Just a quick question, what is the difference between the drag force (Di Felice, 1994) and viscous force used in CFDEM coupling? I am considering the vscous force may be incorporated in the drag force, am I correct?

Best,
Rachel

Hello,

How far away is the public release of superquadric CFD-DEM?

Greetings, Paul

Dear all,

I am a beginner in LIGGGHTS

I am trying to simulate the sediment transport around the pile based
on the reference paper "Shim, J., Duan, J., & Jo, H. (2016).
Simulating Sediment Transport around a Bridge Pier Using Open FOAM
Software. In World Environmental and Water Resources Congress 2016
(pp. 362-369)".

This paper validates by comparing between the simulated the sediment transport and experiment around the pier using CFDEM coupling.

Reynolds number is about 1.8e4. it is laminar flow.

Hello everyone,

I am getting an unphysical pressure field for a few fluidized bed simulations. Everything else (velocity, voidage) seems fine. For most inlet gas velocities, simulations give expected value of pressure. However, for certain flowrate the values are erratic or even negative (possible but not expected) and are so throughout the bed. I am surprised with such fluctuating pressure field how is solution converging?

I am newer of CFDEM, there is a mistake when I run Tutorials. I always get this line:
rm: cannot remove '/home/administrator/CFDEM/administrator-PUBLIC-5.0/run/fillCylinder/CFD/0.*': No such file or directory

and that is the whole running process:
mesh was built before - using old mesh

// run_liggghts_fillCylinder_DEM //

/home/administrator/CFDEM/administrator-PUBLIC-5.0/run/fillCylinder/DEM

I am confused about the momentum coupling options in CFDEM viz implicit/explicit. Following are my questions.

1. what is TotalForceImp displayed in the cfdem log
is this done implicitly? sum(mesh.V()*Ksl.internalField()*(Us.internalField()-U.internalField()));

I ask this because of the next question.

2. On CFD side I have momCoupleModels selected as implicitCouple

While on DEM side for the resume file, I have: fix cfd2 all couple/cfd/force
How is the force calculated in this case? is it done explicitly?

i am newer of cfdem, there is a mistake when i run Tutorials,
it said no 0.* file, but there is a file after i see that folder, functions.sh is same
i don‘t know why