Study on intermolecular transfer mechanism that governs transport characteristics of energy and momentum in fluids

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The purpose of this study is to clarify the microscopic mechanism of molecular scale that governs characteristics of fluids to transport energy and momentum. As the best model fluids for that purpose, a filmwise liquid between solid walls at a highly nonequilibrium state was selected for our molecular dynamics simulation. In this system with a velocity difference given between the solid walls, momentum transport occurs in the Couette-like flow (viscosity in a macroscopic sense) and simultaneously, energy of macroscopic flow is converted to thermal energy, which results in temperature rise (viscous heating in a macroscopic sense) and energy transfer from the liquid to the solid walls. (heat conduction in a macroscopic sense) This simultaneous occurrence of momentum transfer and energy transfer is not only a good model to be analyzed but also important from a view point of application to fluid lubrication. Simulation for a simple liquid clarified;(1) Temperature and velocity jump at the solid-liquid interface due to degraded energy and momentum transfer,(2) Transfer characteristics in liquid in the vicinity of the solid surface, which has a peculiar structure similar to solid,(3) Highly nonequilibrium thermal state in liquid in the vicinity of the solid surface. Especially the above (3) is a first observation of the uneven distribution of thermal energy to each degree of freedom of molecular motion. Such mechanism of nonequilibrium state is much complicated in case of polyatomic molecules that have degrees of freedom in rotational motion. As a first step to analyze this phenomenon, a linear molecule was selected and its transfer characteristics was analyzed.