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DEM simulation of weakly wetted Users committee meeting granular material Short overview of the work done by FG-team imfd DFG-STW, 2014 CONTENT Implementation in Software Capillary bridge models Results of DEM-simulations of

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imfd Users’ committee meeting

“DEM simulation of weakly wetted granular material”

Short overview of the work done by FG-team

SLIDE 2

DFG-STW, 2014

imfd

CONTENT

Implementation in Software Capillary bridge models Results of DEM-simulations of split-bottom shear-cell CFD-simulations of the shear cell Conclusions

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 1

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Implementation in Software

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Yade (Yet Another Dynamic Engine)

Pros

Reliable, modern code OpenMP-parallelization

Cons

Lower calculation speed No MPI-support LIGGGHTS (LAMMPS improved for general granular and granular heat transfer simulations)

Pros

MPI-support High calculation speed

Cons

Some problems with capillary simulations (v2.x) Old-style code

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 2

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Capillary bridge models

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Implemented CBMs:

1. Weigert et al.
2. Willett et al. (full and reduced)
3. Rabinovich et al.

Input constant parameters:

1. Contact angle θ
2. Liquid bridge volume Vb
3. Surface tension γ

Controlled parameter: Separation particle distance s

θ s i j V

Fig. 1:

Capillary bridge schema

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 3

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Capillary bridge models

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Comparison with experiments of Willett et al. 50 100 150 200 250 300 350 50 100 150 200 250 F [µN] a [µm] Weig WilR WilF RabL Exp

Fig. 2:

Comparison of difgerent kinds of capillary bridge models with experimental data from Willett. Rp = 2.381mm, Vb = 13.6nl, θ = 0◦.

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 4

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Results of DEM-simulations of split-bottom shear-cell

imfd

Fig. 3:

Setup of split-bottom confjguration

DEM parameters

Rp = 2.381mm; ρ = 150kg/m3; tc = 5.4 · 10−6s; en = et = 0.83 Particle number ≈ 2 · 105; Rotation period 100s;

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 5

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Results of DEM-simulations of split-bottom shear-cell

imfd

AVERAGING TECHNIQUES

The software to analyze DEM-shear-cell results https://github.com/gladk/rheometeranalyze

RheometerAnalyze

Written in C++ Import of text-data in difgerent formats Export in text-form, VTK External libraries: boost, alglib, vtk, eigen3 Steady state analyze φ = 1 t2 − t1

∫

φdt Snapshots analyze < φ >= 1 ∆t

t+∆t

∫

φdt t2 − t1 >> ∆t

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 6

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Results of DEM-simulations of split-bottom shear-cell

imfd

Typical results from DEM-simulation:

Fig. 4:

Fig. 5:

Fig. 6:

˙ γ

Fig. 7:

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 7

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Results of DEM-simulations of split-bottom shear-cell

imfd

Local shear stress as a function of local pressure: 2 4 6 8 10 10 20 30 40 50 60 70 80 . 1 3 x ( V

= [ n l ] ) . 1 3 x + 2 . ( V

= 7 4 [ n l ] ) . 1 3 x + 1 . 3 ( V

= 1 3 [ n l ] ) τ [Pa] p [Pa]

Fig. 8:

τ(P).

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 8

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Results of DEM-simulations of split-bottom shear-cell

imfd

10 100 0.1 1 η [Pas] ˙ γ [s−1] Dry RabL, 13nl RabL, 74nl

Fig. 9:

Apparent shear viscosity η( ˙ γ) for ˙ γ > 0.02s−1

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 9

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Results of DEM-simulations of split-bottom shear-cell

imfd

Development of the local shear deformation γ:

Fig. 10:

< γ > (t = 0.0225s)

Fig. 11:

< γ > (t = 2.25s)

Fig. 12:

< γ > (t = 4.5s)

Fig. 13:

< γ > (t = 9.0s)

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 10

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Results of DEM-simulations of split-bottom shear-cell

imfd

0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 1 2 3 4 5 6 7 8 Rz ± W [m] t [s] Dry Vb = 13[nl] Vb = 74[nl]

Fig. 14:

Comparison of shear band position and width as a function of time for both weakly wet and dry state

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 11

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CFD-simulations of the shear cell

imfd

Fig. 15:

U(t = 0.01) s

Fig. 16:

U(t = 0.10) s

Fig. 17:

U(t = 0.30) s

Fig. 18:

U(t = 1.00) s

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 12

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CFD-simulations of the shear cell

imfd

−0.2 0.2 0.4 0.6 0.8 1 1.2 50 100 150 200 250 300 ω [s−1] R-position [m] CFD z=0.1h CFD z=0.5h CFD z=1.0h DEM z=0.1h DEM z=0.5h DEM z=1.0h

Fig. 19:

Normalized velocity profjles from CFD and DEM simulations

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 13

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Conclusions

imfd

1. Implement and compare of difgerent capillary bridge models
2. DEM simulations of the shear cell
3. Micro-macro parameter transitions
4. CFD-simulations of the shear cell (fjrst stage)

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 14

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Conclusions

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Thank you for your attention!

TU Bergakademie Freiberg | IMFD | Gladky | DFG-STW, 2014 | 2014-09-25 15