  We present simulations that reveal a surprisingly large effect of
hydrodynamic coupling on the speed of thermal ratchet motors. The model that we
use considers particles performing thermal ratchet motion in a hydrodynamic
solvent. Using particle-based, mesoscopic simulations that maintain local
momentum conservation, we analyze quantitatively how the coupling to the
surrounding fluid affects ratchet motion. We find that coupling can increase
the mean velocity of the moving particles by almost two orders of magnitude,
precisely because ratchet motion has both a diffusive and a deterministic
component. The resulting coupling also leads to the formation of aggregates at
longer times. The correlated motion that we describe increases the efficiency
of motor-delivered cargo transport and we speculate that the mechanism that we
have uncovered may play a key role in speeding up molecular motor-driven
intracellular transport.
