Abstract
In this paper we use molecular dynamics (MD) simulations to study nano- channel flows at low Reynolds numbers and present some new interesting results. We investigated a simple fluid flowing through channels of different shapes at the nano level. The Weeks-Chandler-Anderson potentials with different interaction strength factors are adopted for the interaction forces between fluid-fluid and fluid-wall molecules. In order to keep the temperature at the required level, a Gaussian thermostat is employed in our MD simulations. Comparing velocities and other flow parameters obtained from the MD simulations with those predicted by the classical Navier-Stokes equations at same Reynolds numbers, we find that both results agree with each other qualitatively in the central area of a nanochannel. However, large deviation usually exists in areas far from the core. For certain complex nanochannel flow geometry, the MD simulations reveal the generation and development of nano-size vortices due to the large momenta of molecules in the near-wall region while the traditional Navier-Stokes equations with the non-slip boundary condition at low Reynolds numbers cannot predict the similar phenomena. It is shown that although the Navier-Stokes equations are still partially valid, they fail to give whole details for nanochannel flows.
Highlights
The behavior of a flow at the nanometer scale has been a subject of interest in recent years
We compute the five nanochannel flows with the Reynolds number based on the width of the channel being 3 and 5
The WCA potentials with different interaction strength factors are employed for the interaction forces between fluid-fluid and fluid-wall molecules
Summary
The behavior of a flow at the nanometer scale has been a subject of interest in recent years. The understanding of the physical properties and dynamical behavior of nanochannel flows has great importance on the theoretical study of fluid dynamics and many engineering applications in physics, chemistry, medicine and electronics. It is obvious that when the system length reduces to the nano scale, the behavior of the flow is mainly affected by the movements and structure of many discrete particles. The molecular dynamics (MD) simulation, based on the statistical mechanics of nonequilibrium liquids [1], is an effective way to describe the details of a flow at the nano scale. The role of replacing the continuum description for the nano level flows makes MD a powerful tool to study many fundamental nanofluid problems which may be extremely difficult to be implemented in the laboratory at the present time. Simple or complex channel flows have been investigated by several researchers, e.g. Todd et al [2] and Jabbarzadeh et al [3]
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