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In this thesis, we use nonequilibrium molecular dynamics (NEMD) methods to investigate the structural and dynamic properties of highly confined atomic and polymeric fluids undergoing planar Poiseuille flow. We derive 'method of planes' expressions for pressure tensor and heat flux vector for confined inhomogeneous atomic fluids under the influence of three-body forces. Our derivation is validated against NEMD simulations of a confined atomic fluid acted upon by a two-body Barker-Fisher-Watts force coupled with the Axilrod-Teller three-body force. Our method of planes calculations are in excellent agreement with the equivalent mesoscopic route of integrating the momentum and energy continuity equations directly from the simulation data. Our calculations reveal that three-body forces have an important consequence for the isotropic pressure, but have negligible in�uence on the shear stress and heat flux vector for a confined simple fluid. We use the non-local linear hydrodynamic constitutive model, proposed by Evans and Morriss [1] for computing a viscosity kernel, a function of compact support, for inhomogeneous nonequilibrium fluids. Our results show that the viscosity kernel, �(y), has a peak at y = 0, and gets smaller and decays to zero as y increases. Physically, it means that the strain rate at the location where we want to know the stress contributes most to the stress, and the contribution of the strain rate becomes less significant as the relative distance y increases. We demonstrate that there is a limitation in the model when it is applied to our confined fluids due to the effect of domain restriction on inverse convolution. We study the nanorheology of simple polymeric fluids. Our NEMD simulation results show that sufficiently far from the walls, the radius of gyration for molecules under shear in the middle of the channel follows the power law, Rg / N�, where N is the number of bonds and the exponent has a value � = 0:60�0:04, which is larger than the melt value of 0:5 for a homogeneous equilibrium �uid. Under the conditions simulated, we find that viscous forces dominate the flow, resulting in the onset of plug-like flow velocity pro�les with some wall slippage. An examination of the streaming angular velocity displays a strong correlation with the radius of gyration, being maximum in those regions where Rg is minimum and vice-versa. The angular velocity is shown to be proportional to half the strain rate su�ciently far from the walls, consistent with the behaviour for homogeneous fluids in the linear regime. Finally, we make some concluding remarks and suggestions for future work in the final chapter.

Ce travail vise à étudier les propriétés de transport et le comportement poromécaniquede fluides simples confinés dans des nanopores lamellaires par le biais de simulationsmoléculaires. Pour ce faire, nous avons proposé différents schémas de simulations de ladynamique moléculaire dans des ensembles adaptés aux propriétés étudiées (diffusion demasse, viscosité, force de friction, gonflement …). Il a été note que les propriétés de transportde fluides fortement inhomogènes variaient fortement dans la direction perpendiculaire auxmurs solides. Nous avons alors proposé une approche non-locale permettant de déterminerquantitativement la viscosité locale de fluides inhomogènes à partir du profil de densité etapplicable pour des sphères dures, molles et le fluide de Lennard-Jones. Il a été égalementmontré qu’un fluide de Lennard-Jones fortement confiné pouvait avoir un comportementviscoplastique (et rhéofluidifiant) si un ordre structurel était induit dans le fluide par laposition relative des murs solides. Enfin, nous avons montré qu’une modification importantede la pression de solvatation du fluide confiné peut être induite par cisaillement ce qui peutinduire un gonflement « dynamique » d’un nanopore lamellaire. / This work aims at investigating the transport properties and the poromechanics of simple spherical fluids confined in slit nanopores through molecular simulations. To do so, we have proposed different schemes to perform molecular dynamics simulations in ensembles adequate to deal with the properties we were looking after (mass diffusion, shear viscosity,friction force, swelling …). The transport properties of strongly inhomogeneous fluids were found to be varying with space perpendicularly to the solid walls. We have then proposed a non-local approach to determine quantitatively the local shear viscosity of such inhomogeneous fluids from the density profile applicable from the Hard-Sphere to the Lennard-Jones fluids. In addition, it has been shown that highly confined Lennard-Jones fluid may exhibit a visco-plastic (+ shear thinning) behavior when a strong structural order is induced in the whole confined fluid because of the relative position of the solid walls. Finally, it was demonstrated that shear induced modifications of the solvation pressure of a confined fluid may exist that leads to a “dynamic” swelling when a slit micropore is sheared.