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The zero-density shear viscosity of different types of short Lennard-Jones chains, up to the hexa-decamer, has been evaluated using a non-equilibrium molecular dynamics scheme. Simulations have been performed on chains of variable rigidities going from the fully flexible to the fully rigid chains. Very interestingly, it is found that there exists a universal relation (a power law) between the zero-density viscosity of the Lennard-Jones chains and their radius of gyration whatever the rigidity of the chain and for all tested temperatures (ranging from 2.5 to 6 in reduced units). Furthermore, for the studied range of temperature, it is shown that the zero-density viscosity of both fully flexible chains and fully rigid chains models can be obtained with an accuracy of a few percents knowing only the dimer viscosity and the length of the chain. [ABSTRACT FROM AUTHOR]

In this work, a new algorithm is proposed to compute single particle (infinite dilution) thermodiffusion using nonequilibrium molecular dynamics simulations through the estimation of the thermophoretic force that applies on a solute particle. This scheme is shown to provide consistent results for model nanofluids in the liquid state (spherical nonmetallic nanoparticles+Lennard–Jones fluid) where it appears that thermodiffusion amplitude, as well as thermal conductivity, decreases with nanoparticle concentration. Then, by changing the nature of the nanoparticle (size, mass, and internal stiffness) and that of the solvent (quality and viscosity), various trends are exhibited. In all cases, the single particle thermodiffusion is positive, i.e., the nanoparticle tends to migrate toward the cold area. The single particle thermal diffusion coefficient is shown to be independent of the size of the nanoparticle (diameter of 0.8–4 nm), whereas it increases with the quality of the solvent and is inversely proportional to the viscosity of the fluid. In addition, this coefficient is shown to be independent of the mass of the nanoparticle and to increase with the stiffness of the nanoparticle internal bonds. Besides, for these configurations, the mass diffusion coefficient behavior appears to be consistent with a Stokes–Einstein-like law. [ABSTRACT FROM AUTHOR]

Highlights: [•] Shear viscosity of SF6 has been modeled (from 225.18 to 473.15K up to 51.21MPa). [•] Physically based viscosity models using from 1 to 6 parameters yield good results. [•] Effective repulsive steepness of the SF6 potential is higher than expected. [ABSTRACT FROM AUTHOR]

We consider the implementation of a friction contact angle model in a Navier-Stokes VoF-CSF solver for the simulation of moving contact lines at the nano-scale. A liquid-liquid interface confined in a Couette flow generated by two solid walls moving at the same velocity in opposite directions is considered to discuss the relevance of the friction model. The simulations are compared with a reference case obtained using MD simulations by Qian et al. [46]. We show that the Navier Stokes simulations are able to reproduce the MD simulations for both the interface shape and the velocity field. The appropriate contact line friction is found to be grid convergent and of the same order as the friction measured in MD simulations. A detailed investigation of the interface shape has revealed an auto-similar linear profile in the center of the channel. Close to the wall the interface shape follows the classical Log evolution given by the Cox relation despite the wall confinement. • A contact line friction model is developed for a Navier–Stokes VoF–CSF solver. • Navier–Stokes with appropriate friction is able to simulate a two-phase Nano-scale Couette flow. • Contact line friction is grid convergent and similar to Molecular Dynamics simulations values. • The interface shape is auto-similar in channel center and follows the Cox solution near the wall. [ABSTRACT FROM AUTHOR]

A thermodiffusion cell is developed for performing Soret experiments on binary mixtures at high pressure and in the presence of a porous medium. The cell is validated by performing experiments at atmospheric pressure. The experiments are performed by applying different temperature gradients to binary mixtures in order to determine their thermal contrast factor. These measurements provide a first demonstration of the good reproducibility of this kind of measurements upon calibration. [ABSTRACT FROM AUTHOR]

Abstract: This work reports new density data (178 points) of 1-butanol at twelve temperatures between 293.15 and 403.15K (every 10K), and fifteen pressures from 0.1 up to 140MPa (every 10MPa). An Anton Paar vibrating tube densimeter, calibrated with an uncertainty of ±0.5kgm−3 was used to perform these measurements. The experimental density data were fitted with the Tait-like equation with low standard deviations. In addition, the isobaric thermal expansivity and the isothermal compressibility have been derived from the Tait-like equation. [Copyright &y& Elsevier]

Sorer effect in multicomponent system (more than 2 components) are being studied starting from binary solutions. Possible predictive theories are extensions of the thermodynamic theories, molecular dynamics, but also by the mechanical statistics extensions. The latter are illustrated at the light of the experiments obtained in microgravity conditions. For binary melts, a very good concordance between measurements on samples processed in microgravity and the statistical theory is obtained under the form of thermodiffusion factors as function of mass misfit. The same approach is used for hydrocarbon ternary and quaternary solution processed in microgravity in the SCCO experiment. [ABSTRACT FROM AUTHOR]

This paper describes the European Space Agency (ESA) experiments devoted to study thermodiffusion of fluid mixtures in microgravity environment, where sedimentation and convection do not affect the mass flow induced by the Soret effect. First, the experiments performed on binary mixtures in the IVIDIL and GRADFLEX experiments are described. Then, further experiments on ternary mixtures and complex fluids performed in DCMIX and planned to be performed in the context of the NEUF-DIX project are presented. Finally, multi-component mixtures studied in the SCCO project are detailed. [ABSTRACT FROM AUTHOR]