title: Departure of microscopic friction from macroscopic drag in molecular fluid dynamics.
abstract: Friction coefficient of the Langevin equation and drag of spherical macroscopic objects in steady flow at low Reynolds numbers are usually regarded as equivalent. We show that the microscopic friction can be different from the macroscopic drag when the mass is taken into account for particles with comparable scale to the surrounding fluid molecules. We illustrate it numerically by molecular dynamics simulation of chloride ion in water. Friction variation by the atomistic mass effect beyond the Langevin regime can be of use in the drag reduction technology as well as the electro or thermophoresis.
authors.affiliation: Institute of Engineering, Tokyo University of Agriculture and Technology, Naka-cho 2-24-16, Koganei, Tokyo 184-8588, Japan.
authors.forename: Itsuo
authors.initials: I
authors.lastname: Hanasaki
authors.affiliation: Graduate School of Engineering Science, Osaka University, Machikaneyama-cho 1-3, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Fujiwara
authors.affiliation: Graduate School of Engineering Science, Osaka University, Machikaneyama-cho 1-3, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Satoyuki
authors.initials: S
authors.lastname: Kawano