Tests of dynamical scaling in three-dimensional spinodal decomposition

We simulate late-stage coarsening of a three-dimensional symmetric binary fluid. With reduced units $l,t$ (with scales set by viscosity, density, and surface tension) our data extends two decades in t beyond earlier work. Across at least four decades, our own and others’ individual datasets $(<\mathrm{}1\mathrm{}$ decade each) show viscous hydrodynamic scaling $(l\sim a+bt),$ but b is not constant between runs as this scaling demands. This betrays either the unexpected intrusion of a discretization (or molecular) lengthscale, or an exceptionally slow crossover between viscous and inertial regimes.