Friction factor in nanochannel flows

Abstract

Non-equilibrium molecular dynamics simulations are employed in order to access the detailed atomic behavior of fluids moving in nanochannels and to quantify the associated energy dissipation. Nanochannels of various degrees of wall hydrophobicity/hydrophilicity and roughness are studied. Dimensional arguments that include the role of the atomistic model parameters allow us to derive a functional expression for the Darcy–Weisbach friction factor, f, so that macroscopic flow estimates of f can be compared to those for nanochannel flows. The NEMD simulations allow us to take into account parameters such as wall/fluid interaction which are neglected in the macroscopic theories and embed proposed modifications in classical relations. The methodology forms the basis for generating Moody’s-like diagrams for nanoscale conduit flows where the range of the relative roughness parameter is significantly larger than in macroflows. © 2016, Springer-Verlag Berlin Heidelberg.