Molecular dynamics simulation on the splitting of shear flow in nanochannels

With the vigorous development of micro-/nanoscience and micro-/nanotechnology, fluid flows at the micro-/nanoscale have become an important research field. The molecular dynamics simulations of Couette flow in a nanochannel are carried out in this paper. In order to evaluate the non-equilibrium effect of the rarefied flow field, a “sampling-classification” method is proposed. Through this newly developed method, we found that the rarefied gas flow in nanochannels can be regarded as the superposition of two independent shear flows with the same shear rate. A nondimensional quantity “vd” is proposed to quantificationally evaluate the degree of splitting, or more specifically, the non-equilibrium state, of the flow field. Further study shows that the growth in roughness will aggravate this rarefied non-equilibrium effect, while the increase in system temperature leads to an opposite result. The “sampling-classification” method developed in this article can provide a new analytical idea for subsequent rarefied flow researchers, and the splittable phenomenon of shear flow discovered can also be regarded as an important property of rarefied flows that is worthy of further study.