Thermodynamics and Hydrodynamics for a Modeled Fluid

This article presents a general study of a two‐dimensional fluid model with microscopic discrete velocities. The rather unusual properties of this model lead to precise thermodynamical laws. The Navier‐Stokes hydrodynamical equations are obtained, which contain a transport coefficient given by a Green‐Kubo integral, and it is shown that this integral does not converge for a reason common to all two‐dimensional fluids.