Effects of density inhomogeneities and non-locality on nanofluidic flow

We use Molecular Dynamics computer simulations to investigate the effects of strong density inhomogeneities on shearing flow in unconfined simple atomic fluids. We use a sinusoidal longitudinal force (SLF) to produce periodic, spatially oscillating density inhomogeneities that have periodic cycles of the order of single or few atomic diameters. We use a sinusoidal transverse force (STF) to produce spatially periodic shearing flow. Using the SLF and STF in combination we can produce shearing flow in strongly inhomogeneous fluids. This system is ideal for investigating the coupling relationships that are known to exist between density and velocity gradients. It is ideal because it provides us with full control over the density profiles and because we can easily decompose the periodic density, velocity, temperature and shear pressure profiles into individual Fourier components. <br><br>Another system for studying strongly inhomogeneous shearing fluids is a nanoconfined system, where a fluid is forced to flow through a nanochannel or nanopore. In these systems, where it is known that the coupling between density and velocity gradients has a significant effect on the fluid hydrodynamics, we do not have control over the density and we cannot easily decompose the flow profiles. This makes the combined STF-SLF method a valuable tool for investigating density-velocity coupling in nanofluidic systems. Using the STF and SLF we are able to probe the non-local density, strain rate and shear pressure response of an atomic fluid to an external body force directly in Fourier space. In this way we can evaluate various linear and nonlinear response functions, which describe the formation of shearing flow and density inhomogeneities in homogeneous, equilibrium fluids when perturbed by external body forces.<br><br>