Simulation of low speed 3D nanochannel flow

This paper presents a new technique of simulating low speed nanochannel flows using molecular dynamics simulation (MDS) method. When using the molecular dynamics simulation method to study low speed nanoscale flow problems, a major difficulty is the extraction of the true flow velocity because of the highly nonlinear coupling of the low bulk flow velocity and the high velocity of molecules’ thermal motion. In all published papers the reported flow velocity is the average value of the sum of these two velocities over time. For high speed flow problems the conventional MDS method can give satisfactory result. However, when the flow velocity is much smaller than the thermal velocity, the conventional molecular dynamics simulation method cannot predict the true flow velocity. To overcome this difficulty, in this study, a new linearized algorithm is developed. The new algorithm separates the flow velocity increment caused by external forces from the thermal motion velocity at each time step. The detailed process of the new algorithm is derived in this paper and several cases of 3D nanochannel flows of liquid argon are simulated by using this method. The numerical results show that the new algorithm is valid for nanoscale flows.