Tests of dynamical scaling in three-dimensional spinodal decomposition

We simulate late-stage coarsening of a three-dimensional symmetric binary f luid. With reduced units l,t (with scales set by viscosity, density, and su rface tension) our data extends two decades in t beyond earlier work. Acros s at least four decades, our own and others' individual datasets (<1 decade each) show viscous hydrodynamic scaling (l similar to a+bt), but b is not constant between runs as this scaling demands. This betrays either the unex pected intrusion of a discretization (or molecular) lengthscale, or an exce ptionally slow crossover between viscous and inertial regimes. [S1063-651X( 99)51102-1].