Mechanics of granular column collapse in fluid
Krishna Kumar, krishnak@utexas.edu
University of Texas at Austin, USA.
Jean-Yves Delenne, INRA, University of Montpellier 2, France.
Kenichi Soga, University of California, Berkeley.
EMI 2019, Pasadena, CA
19th June 2019
Mechanism of submarine landslides
Modelling Test at 1g Condition
- Material type influences the mode of the flow.
- Target: Clay‐rich flow (Less diffusive, Hydroplaning).
LBM - DEM simulation of granular collapse in a 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 a fluid: Effect of aspect ratio
aspect ratio 'a' of 0.4
aspect ratio 'a' of 4
Collapse in a fluid: Runout evolution
Critical time $\tau_c=\sqrt{H/g}$ (Staron and Hinch, 2005)
where, H = Height of the granular pile.
Runout: dry vs fluid
Collapse on an inclined plane
aspect ratio 'a' of 6 on a slope of 5*
Collapse of a dense column on an inclined plane
Collapse of a dense column on an inclined plane
Collapse of a dense column on slopes: runout
Collapse of a loose column on slopes: runout
Loose v dense: Initiation phase
Loose v dense: Initiation phase
Pore-pressure distribution along the failure plane during initiation.
Loose v dense: Runout phase
Loose v dense: Runout phase
Water entrainment front (~15d length) at a slope of 5*
Loose v dense: Runout phase
Loose v dense: Effective stresses
Loose v dense: Settlement phase
Loose v dense: Kinetic energy evolution
Collapse on slopes: loose v dense
LBM - DEM a = 0.8 & 10,000 particles
- LBM Nodes = 50 Million : DEM grains = 10000 discs
- Run-time = 4 hours
- Speedup = 125x on a Pascal P100