| With the development of modern science and nanotechnology, the behavior of nanoscale fluid has been attracting more and more attention. As the difficulties of experimental and theoretical studies, molecular dynamics simulations has been a powerful tool to explore nanoflow problems. In the process of studying flow characteristics, how to extract the true flow velocity is a major difficulty. The flow velocity got by traditional molecular dynamics method is the average value of bulk flow velocity and the molecules'thermal motion over time. This method only can apply in the case of high speed flow problems. For low speed flow problems, because of the highly nonlinear coupling of the low bulk flow velocity and the high velocity of molecules'thermal motion, and usually over-estimate the true flow velocity in such cases and lose its authenticity. Calculation of flow velocity in low speed nanoflow problems is the basis for nanoflow problems, so the successful resolution of this issue has great significance.In the paper, firstly, two kinds of solution method of flow velocity in nanoflow system were described and compared, and combine Newton's law of internal friction and molecular dynamics method, Three-dimensional liquid argon Poiseuille flows in circular cross sectional nanochannels are simulated and the flow characteristics are studyed with this new method. By changing the radial size of flow model and external force and wall-fluid interaction, established a number of simulated examples. Simulation results show that: high-speed flows, the flow velocities obtained by the new method are close to conventional results, for low speed flows, the flow velocities calculated by the new method are still stable. By simulation, focused on the effect of the radial size of flow model and external force and wall-fluid interaction, We mainly pay attention to density and viscosity and shear stress and flow velocity distribution, and get a number of important conclusions by comparing. |
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