Simulation of Pressure-Driven Flows in Nanochannels Using Multiparticle Collision Dynamics

Abstract

A multiparticle collision dynamics algorithm is presented to simulate gas flow in nanoscopic channels with a square cross section. Special attention is given to the definition of inlet and outlet regions of the simulated system and the boundary conditions that are appropriate to describe flow through the nonequilibrium, open system. The boundary conditions are designed to use only physically relevant, readily measurable quantities as input, such as the pressure drop between ends of the channel, the mass flow rate, and the temperature at the input and output. Particular care is taken to minimize the propagation of entrance and exit artifacts due to the inlet and outlet regions by using Navier-Stokes solutions for the expected velocity profile in the first inlet cell. In addition, a collision operator is introduced to simulate an adiabatic diffusive boundary condition to facilitate the study of energy flow through the channel in the absence of thermalizing walls. The results of simulations over a range of conditions are compared to series solutions of the Navier-Stokes equation both with and without slip boundary conditions for isothermal compressible fluid flow in a square channel. The results of the particle-based simulation agree well with the slip boundary condition solution, although the assumption of isothermal flow begins to fail and deviations between the solution and simulation results begin to emerge under high pressure gradients.