Drag reduction by nanobubble clusters as affected by surface wettability and flow velocity: Molecular dynamics simulation

Abstract The molecular-dynamics simulation of a ternary (solid–liquid–gas) system was performed to investigate the nucleation of nanobubble clusters and the effect of nanobubble flow on nanochannels. Results showed that the existence of gaseous nanobubbles can replace the dense and orderly absorbed liquid layer in nonbubble flow. Nanochannels with various surface wettabilities were compared. For the hydrophilic surface, nanobubbles were attracted by the solid surface with a large contact angle, and density fluctuations near the surface decreased. Conversely, the hydrophilic surface exhibited repulsion toward nanobubbles. Simulation results indicated that surface wettability may be enhanced toward its intrinsic property with increased driving velocity. Moreover, introducing the hydrophobic property coupled with high velocity had a dramatic positive effect on drag reduction.