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Fluidized piston model for molecular dynamics simulations of hydrodynamic flow

We have developed a new method, the fluidized piston model (FPM), to drive dense fluid flow in molecular dynamics (MD) simulations. Fluid in the upstream region acts as a fluidized piston (FP) that continuously presses and supplies the downstream fluid. The FPM can treat dense and polyatomic fluid flow driven by a pressure gradient efficiently with the prescribed inlet streaming velocity at high speed, which is usually used for hydrodynamic MD studies. Furthermore, the temperature inside the sampling region is kept constant without direct control. We apply the FPM to the 100 m s−1 water flow inside (20, 20), (12, 12), (10, 10), (8, 8) and (6, 6) carbon nanotubes (CNTs). The results show that the appropriate density in the sampling region is adaptively obtained during the simulation and the desired streaming velocity is obtained except inside the (6,6) CNT. The deviation of the obtained streaming velocity from the desired value inside the (6,6) CNT is related to the current technical limit of the temperature control method applied in the upstream FP region and the highly discrete nature of the single-file water flow.