Large deformation modelling of granular flows
MPM and LBM-DEM
Krishna Kumar, kks32@cam.ac.uk
University of Cambridge
Kenichi Soga, soga@berkeley.edu
University of California, Berkeley.
Special Interest Group - Granular Flows
31 March 2017.
Cambridge-Berkeley Computational Geomechanics
- Lattice-Boltzmann + Discrete Element Method
- Finite Element Method - Thermo-Hydro Mechanical Coupling
- Material Point Method
- Lattice Element Method
Aerial landslides
Experimental results (Lube et al., 2004)
Material Point Method
Micro to Macro
MPM v DEM column collapse
DEM column collapse
MPM slope failure due to pore-pressure
Selborne slope cutting experiment
MPM underwater slope failure (Taka, 2012)
Mechanism of submarine landslides
Modelling Test at 1g Condition
- Material type influences the mode of the flow.
- Target: Clay‐rich flow (Less diffusive, Hydroplaning).
MPM underwater slope failure (Taka, 2012)
LBM - DEM simulation of granular collapse in fluid
aspect ratio 'a' of 6
Lattice Boltzmann - MRT
\[f_{i}(x + dx, t +\Delta t) - f_{i}(x, t) = -S_{\alpha i}(
f_{i}(x, t) - f_{i} ^ {eq}(x, t))\]
- $S_{\alpha i}$ is the collisional matrix.
- Probability density of finding a particle : $f(x,\varepsilon, t) $, where, x is position, $\varepsilon$ is velocity, and t is time.
Granular collapse in fluid: Effect of aspect ratio
aspect ratio 'a' of 0.4
aspect ratio 'a' of 4
Runout: dry vs. fluid
Collapse in fluid: Effect of permeability
Reduction ‘r’=0.7R
Reduction ‘r’=0.9R
Runout: effect of permeability
Effect of permeability: runout
Effect of permeability: runout
Collapse on an inclined plane
aspect ratio 'a' of 6 on a slope of 5*
LBM - DEM a = 0.8 & 10,000 partilces
- LBM Nodes = 50 Million : DEM grains = 10000 discs
- Real-time = 2 seconds
- Run-time = 4 hours
- Speedup = 25x on a Tesla K20
2D to 3D
LBM multi-component multi-phase
Thank you!
Krishna Kumar, kks32@cam.ac.uk
www.cb-geo.com