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A. Gladkyy, S. Roy, T. Weinhart, S. Luding, R. SchwarzeTU Bergakademie FreibergLampadiusstrasse 409599 FreibergGermany

DEM simulations ofweakly wetted granular materials:implementation of capillary bridge models

September 28-30, 2015, Barcelona, Spain

IV Conference on Particle-Based Methods, Particles 2015

TU Bergakademie Freiberg

Situated in the city of Freiberg, Saxony, Germany6 faculties, 5600 students, 86 professors2 collaborative research centersInstitute of Mechanics and Fluid Dynamics:

Applied Mechanics: Solid Mechanics, DynamicsFluid Mechanics, TurbomachineryNumerical modelling of granular flow processes:CFD, DEM, SPH

Source: https://commons.wikimedia.org/wiki/File:Weisbachbau_Freiberg_TU_Bergakademie.jpg2015-09-{28…30}PARTICLES 2015

Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 1

Discrete element model with capillary bridges

jω

ωi

rj

v j

ri

v i

R

R

lijc

mPd⃗vdt =

∑c

f⃗c + mPg⃗

IPdω⃗dt =

∑c

(⃗lc × f⃗c

)

f⃗n =

(−knδn − γn

dδndt + fcap

)n̂

f⃗t = min[−ktδt − γt

dδtdt , µfn

]t̂

S+ =a

2√

V/R

fcap =2πRγ cos θ

1 + 2.1(S+) + 10(S+)2Willett formulation(see Gladkyy, Schwarze 2014 for details)

Ri Rj

β

R1

R2

a

Θ

dsp/sp

α

i j

2015-09-{28…30}PARTICLES 2015

Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 2

Split-bottom shear cell configuration

Fig. 1: Setup of split-bottom configuration (see Gladkyy, Schwarze 2014 for details)

DEM parameters

Dp = 2.2 mm; ρ = 2000 kg m−3; kn = 110 N m−1; kt = 12 N m−1;γn = 0.002 kg s−1; γt = 0.0005 kg s−1; θ = 20°; γ = 20.6 mN m−1;Particle number ≈ 145000; Rotation 0.6 RPM; Vb =0 nl to 200 nl;

2015-09-{28…30}PARTICLES 2015

Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 3

DEM open-source software

MercuryDPM, YADE, LIGGGHTS

Computational parts are written in C++, running on Linux/UnixParallelization (MPI, OpenMP)Free GPL (v. 2 and v. 3) licensesData export into different formats, including VTKReach functions for work with complex geometriesParticle import/export and generation opportunitiesAvailable in Debian/Ubuntu repositories (YADE, LIGGGHTS)CMake build system

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Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 4

DEM open-source software

MercuryDPM: http://mercurydpm.org

C++ for the simulation setup and scenarioContributors: University of Twente (The Netherlands), community

Yet Another Dynamic Engine (YADE): http://yade-dem.org

Python bindings for simulation setup, control and postprocessingOpenMP; GUI for simulation setup and controlContributors: community (Lab 3SR - Grenoble, CTU Prague, TU Freiberg …)

LIGGGHTS (LAMMPS improved for general granular and granular heat transfer simulations): http://liggghts.com

Own scripting language for simulation setupMPI; coupling with CFD-code, SPH-model, heat-transferContributors: DCS Computing, community (TU Graz, JKU Linz …)

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Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 5

Implementation of capillary bridge models

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Velocity profile compare

0

0.2

0.4

0.6

0.8

1

20 30 40 50 60 70 80 90 100 110

ω/ω

0 [-

]

r [mm]

MercuryDPMYade

Liggghts

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Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 7

Contact number probability

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 2 4 6 8 10

Pro

babi

lity

[-]

Contact number [-]

MercuryDPMYade

Liggghts

0 4 8 12 16

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Water content

0.01

0.1

1

10

0 50 100 150 200

Wat

er c

onte

nt [%

]

Bridge volume [nl]

MercuryDPMYade

Liggghts

2015-09-{28…30}PARTICLES 2015

Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 9

Conclusions

Good practice in writing open-source programs

Before starting a new program, try to join existing project.Do not invent your own license (DFSG).Only source files in the tarball, build everything from source.Avoid inclusion of 3rd-party codes.Document dependencies.Use proper versioning and prepare releases.Have an automatic test suit.Use build system: autoconf and automake, cmake.

https://wiki.debian.org/UpstreamGuide

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Gladkyy, Roy, Weinhart, Luding, Schwarze IMFDTU Bergakademie Freiberg 10

Thank you for your attention!

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