Geochemistry Department Movies

Lattice Gas Automata and Lattice Boltzmann Movies

Rayleigh-Taylor instability (80k) Two imiscible fluids in contact along a horizontal boundary in the presence of gravity. Initially the dense fluid is on top.

Dispersion due to flow in a porous medium (92k) Watch the thunderbird disappear!

Dispersion in a planar channel(158k) (1) symmetric dispersion, no density difference; (2) dispersion when tracer is 1% denser than carrier fluid.

Viscous fingering in a porous medium (1915k) Red fluid is 8 times as viscous as blue, but has same density.

Rayleigh-Taylor for MISCIBLE liquids (161 kb) This calculation shows the advantage of the BGK Lattice Boltzmann (LB) method over LGA. A heavy (black) fluid initially overlies a less-dense white fluid. A small bump in the interface initiates mixing. With LB methods, the diffusion coefficient can be arbitrarily tuned, independent of the viscosity; thus the fine swirls of white "smoke" stay distinct, even in this simulation which contains only 128x128 nodes. In the LB method, it is easy to add an arbitrary number of chemical components, and to give the components different diffusion coefficients.

Double-Diffusive Fingering (195kb) "Salt fingering" is an important mechanism of mixing in the oceans, and can be modeled with sugar and salt solutions in Hele-Shaw cells. In this LB calculation, the lower red fluid ("salt solution") is initially denser than the upper blue fluid ("sugar solution"), so the system is gravitationally stable. However, the salt diffusion coefficient is 3 times higher than the sugar coefficient, so a salt-poor, lower-density region forms below the interface, leading to gravitational instability and fingering. The calculation uses a speed-dependent drag term (after Holme and Rothman) to mimic Hele-Shaw flow.

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