  We use molecular dynamics (MD) simulations to study surface-directed spinodal
decomposition (SDSD) in unstable binary ($AB$) fluid mixtures at wetting
surfaces. The thickness of the wetting layer $R_1$ grows with time $t$ as a
power-law ($R_1 \sim t^\theta$). We find that hydrodynamic effects result in a
crossover of the growth exponent from $\theta\simeq 1/3$ to $\theta\simeq1$. We
also present results for the layer-wise correlation functions and domain length
scales.
