Slip length of branched hydrocarbon oils confined between iron surfaces.

• Nonequilibrium Molecular Dynamics simulation of a shear flow emphasizing the effect of the molecule branches. • Investigation of polyalphaolefin base oil wall sliding confined between iron surfaces. • Effect of temperature on the polyalphaolefin-iron lubrication system. In this paper, the slip length of branched hydrocarbon molecules, i.e., polyalphaolefin oils, under shear in a gap between iron surfaces were investigated utilizing large-scale Molecular Dynamics (MD) simulation. The results showed the expected singularity for the slip length with variation gap height. For large gap height, h → ∞ , the slip length approaches a constant asymptote λ → λ ∞. This study indicated that as the number of branches of the liquid molecule raise, the slip length λ → λ ∞ as well as viscosity increases. For given apparent shear rate, the friction force increased with increasing temperature due to the reduction of wall slip. MD Simulations demonstrate that the slip length of the polyalphaolefin-iron system increase by decreasing the liquid temperature, indicating an Arrhenius process. [ABSTRACT FROM AUTHOR]