Synchronized molecular-dynamics simulation for the thermal lubrication of a polymeric liquid between parallel plates

Abstract

The Synchronized Molecular-Dynamics simulation which was recently proposed by authors [Phys. Rev. X 4, 041011 (2014)] is applied to the analysis of polymer lubrication between parallel plates. The rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with changing the values of thermal conductivity of the polymeric liquid. It is found that at a small applied shear stress on the plate, the temperature of polymeric liquid only slightly increases in inverse proportion to the thermal conductivity and the apparent viscosity of polymeric liquid is not much affected by changing the thermal conductivity.However, at a large shear stress, the transitional behaviors of the polymeric liquid occur due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme-Griffith number Na which is defined as the ratio of the viscous * Email: yasuda@sim.u-hyogo.ac.jp, Tel/Fax +81(0)783031990 Preprint submitted to ElsevierMarch 30, 2018 heating to the thermal conduction at a characteristic temperature. When the Nahme-Griffith number exceeds the unity, the temperature of polymeric liquid increases rapidly and the apparent viscosity also exponentially decreases as the thermal conductivity decreases. The conformation of polymer chains is stretched and aligned by the shear flow for Na < 1, but the coherent structure becomes disturbed by the thermal motion of molecules for Na > 1.

Synchronized Molecular-Dynamics Simulation of the Thermal Lubrication of an Entangled Polymeric Liquid

“…In this paper, we tackle the thermal lubrication of entangled polymer chains by using the SMD method. This study is the extension of a series of previous studies on an unentangled polymer fluid [22,23,24] to the entangled polymer fluid. In the previous studies, a counter-intuitive transitional behavior induced by viscous heating was discovered in the dynamics of polymer conformation.…”

A Review on Transport Phenomena of Entangled Polymeric Liquids

“…[124][125][126] More recently, Yasuda and Yamamoto developed the synchronized molecular dynamics (SMD) method that can address flow problems of complex fluids with temperature changes. [127][128][129] In the SMD, the KG simulations of local fluid elements are synchronized to satisfy the macroscopic momentum and energy equations at a macroscopic time interval. Using the SMD method, lubrication problems of unentangled 127,128) and weakly entangled 129) polymer melts were investigated.…”

“…[127][128][129] In the SMD, the KG simulations of local fluid elements are synchronized to satisfy the macroscopic momentum and energy equations at a macroscopic time interval. Using the SMD method, lubrication problems of unentangled 127,128) and weakly entangled 129) polymer melts were investigated.…”

Solidification of the Lennard-Jones fluid near a wall in thermohydrodynamic lubrication

“…Incidentally, the multiscale hybrid method of MD and CFD is currently a very active research field [12][13][14][15][16][17][18][19][20][21][22]. The thermohydrodynamic lubrication of polymeric fluids was also investigated by the synchronized MD method, in which a transitional behavior of the polymer conformation due to thermohydrodynamic coupling was clarified [23][24][25]. Although the multiscale approach is powerful and promising for complex fluids, to further develop the multiscale method, we require more first-principles results obtained through MD simulations.…”