Lattice Gas Cellular Automata Fluid Dynamics: The Model of Frisch, Hasslacher, and Pomeau

In the November 2020 “Your Homework Assignment” column in Computing in Science & Engineering, the reader was introduced to the cellular automata fluid model of Hardy, Pomeau, and de Pazzis. Although their model captures the microscopic behavior of particles, the square grid restricts the possible interactions such that the model cannot reproduce the Navier–Stokes equations in the continuous limit. Thus, for a more accurate fluid simulation, we need a more complex grid that allows for more particle interaction. Here the lattice gas cellular automata model of Frisch, Hasslacher, and Pomeau is shown. This model uses a hexagonal grid of cells, allowing particles to propagate in six possible directions, thus increasing the degrees of freedom and accuracy of the simulation. The final result will be a simulation of a Kármán vortex sheet, a phenomenon that simpler models are unable to capture.