Roughness effect on flow and thermal boundaries in microchannel/nanochannel flow using molecular dynamics-continuum hybrid simulation

Our molecular dynamics-continuum hybrid simulation method is further validated in terms of flexibility in domain decomposition. The roughness effects on the flow and thermal boundaries in liquid channel flow is studied. The results indicate that the molecules in the wall-neighboring area can be firmly confined in the concaves due to geometric structure and strong liquid-solid interaction and cause locking boundary in the velocity profile and linear gradient in the temperature profile. The locking boundary can further lead to negative slip length, which varies in power law with channel height. The linear temperature gradient, as well as nearly constant temperature jump, can lead to obviously increasing Kapitza length versus channel height. Analysis on flow friction shows that the confinement on the molecules will equivalently narrow the channel, where larger pressure gradient is needed. Therefore, the roughness should be strictly restricted within a range shrinking correspondingly with channel height if the flow condition is supposed to be maintained unchanged. Finally, our hybrid simulation is compared with full molecular dynamics simulation in terms of computational efficiency. Great advantages of the hybrid simulation, such as exclusively flexibility and combination characteristics, demonstrate its potential values and promising applications in the field of microfluidics/nanofluidics.