Fluid Interaction Research Articles

185 Deuterium MRI for CSF Studies in Normal and Hydrocephalic Rats

INTRODUCTION: The recent characterization of the glymphatic system has revived interest in the interaction of cerebrospinal fluid (CSF) with brain tissue via perivascular spaces. Traditional CSF tracers, such as gadolinium and iohexal, are large molecules that do not cross the blood brain barrier (BBB). The primary component of CSF, however, is water, which is BBB permeable. METHODS: Eight adult male rats underwent cisterna magna catheterization for intrathecal infusion. Brain MR images were obtained in a 7 tesla small-animal MRI system. Temporal T1-weighted images (T1WI) were obtained before, during, and after intrathecal infusion of D2O. Five rats then underwent ventricular kaolin injection for induction of hydrocephalus, after which repeat imaging with intrathecal D2O infusion was performed. RESULTS: Intrathecal deuterium infusion produced consistent changes on MRI imaging. Because conventional MRI does not sense deuterium, the T1WI showed a loss in proton signal with D2O infusion. Rapid D2O uptake of <2.5 minutes was noted in CSF spaces, brain tissue, and saggital and straight venous sinuses. CONCLUSIONS: Use of deuterium as an intrathecal contrast agent provides a physiologically realistic model of CSF behavior. Efforts are ongoing to quantify the relationship between MRI signal loss and deuterium tissue concentration for comparative analysis between healthy and hydrocephalic rats. The loss of MRI signal in the straight sinus after intrathecal infusion implicates the deep venous system in the clearance of CSF, suggesting that CSF is reabsorbed into the venous system via the brain tissue itself. Because traditional CSF tracers do not cross the BBB, the role of the brain tissue in the reabsorption of CSF has been overlooked.

Viscosities of inhomogeneous systems from generalized entropy scaling

This study extends entropy scaling to inhomogeneous fluids by using the classical density functional theory together with a new viscosity reference that takes into account the influence of solid–fluid interactions on the fluid viscosity. The density functional theory uses a Helmholtz energy functional based on the perturbed-chain statistical associating fluid theory; the local residual entropy per particle is determined from the temperature derivative of the Helmholtz energy functional in combination with an appropriate weighted density profile. The weighted density calculation requires a single transferable parameter, which is adjusted to a reference molecular dynamics simulation. In particular, local viscosity values for fluids under nanoconfinement near solid–fluid interfaces are predicted using the same entropy scaling parameters as for homogeneous fluids. We validate the model by comparing viscosity and velocity profiles with results from non-equilibrium molecular dynamics simulations of a Couette flow in a slit pore. Good agreement is found between the entropy scaling model and the non-equilibrium molecular dynamics results for both the viscosity and velocity profiles of the Lennard–Jones truncated and shifted fluid. The proposed model extrapolates well to systems with different temperatures, fluid densities, and shear forces as well as to systems with different wetting behaviors. These results demonstrate that entropy scaling can be generalized to inhomogeneous fluids using an appropriate combination of residual entropy profile and viscosity reference.

Characterizing the formation and cross-contamination potential of multi-species biofilms in poultry processing environments: S. Enteritidis, C. jejuni and C. perfringens

This study investigated the cross-contamination dynamics of biofilms preformed on stainless steel (SS) coupons on chicken skin and chicken meat by modeling surface-to-food transfer by contact and surface-to-food transfer in fluids. Additionally, mono-, dual-, and multi-species biofilms were examined to understand the effects of environmental conditions on biofilm-forming abilities. The results of crystal violet (CV) assay revealed that a dual-species biofilm of Salmonella Enteritidis with Campylobacter jejuni and a multi-species biofilm of S. Enteritidis with C. jejuni and Clostridium perfringens cultivated for 72 h under aerobic conditions exhibited significantly higher biofilm-forming abilities than the other biofilm types. Consistent with the CV assay findings, the multi-species biofilm exhibited significantly higher extracellular DNA and protein levels than the other biofilm types. Furthermore, the results highlighted the significant increase in cultivable counts when S. Enteritidis formed dual- or multi-species biofilms with C. jejuni or C. perfringens, indicating a synergistic effect among the strains. Additionally, the analysis of cross-contamination models revealed that the pressing method induced greater cross-contamination across most biofilm types irrespective of the food sample or biofilm characteristics. This suggests that surface-to-food contact played a more influential role in cross-contamination than surface-to-food interactions in fluids. Overall, our findings provide insights into the intricate dynamics of preformed biofilms on SS coupons in contact with chicken skin and meat, underscoring the significance of the relationship between biofilm formation and cross-contamination.

Genetic association between carbonates and gold precipitation mechanisms in the Jinshan deposit, eastern Jiangnan orogen

Carbonates have been traditionally regarded as post-ore minerals in hydrothermal deposits, but they can also occur in pre- and syn-ore stages. However, the genetic relationships between multistage carbonates and gold precipitation mechanisms remain unclear. The Jinshan gold deposit, the largest gold deposit in the eastern Jiangnan orogen, is characterized by the occurrence of abundant hydrothermal carbonates. The nature of the carbonates, especially their association with gold precipitation, was examined in this study through petrographic and geochemical analyses as well as geochemical modeling. Field and petrographic work recognized four paragenesis stages in the Jinshan deposit: (1) quartz (Q1)-carbonate, (2) pyrite-quartz (Q2), (3) gold-polysulfide-quartz (Q3)-carbonate, and (4) chlorite-quartz (Q4)-carbonate. Carbonates associated with gold mineralization are mainly present in the first and third stages. Among them, the first-stage carbonates are pre-ore ankerites (Ank1), which are generally crosscut by syn-ore sulfides. Such carbonates mostly occur in altered host rocks that are characterized by bleaching. Mineralogical and geochemical analyses revealed that chlorite was consumed while ankerite was produced, and Fe contents of the host rocks remained generally unchanged during alteration. Consequently, ankerite (Ank1) is interpreted to have been generated by the interaction of CO2-bearing fluids and chlorite in the host rocks. Geochemical modeling revealed that both Fe-bearing chlorite and ankerite (Ank1) can lead to gold precipitation by triggering sulfidation, but ankerite has higher chemical reactivity and therefore is kinetically favorable for more efficient gold deposition. Syn-ore carbonates were mainly formed in the third stage, primarily consisting of ankerite (Ank2) with minor calcite, and they were coprecipitated with native gold, galena, sphalerite, and chalcopyrite. Two stages of carbonates shared similar δ13CVPDB values and Pb, Zn, and Cu contents but different Ca, Mg, Mn, and Sr contents, indicating they formed at different stages of the same hydrothermal event. Geochemical modeling demonstrated that pH increases, as indicated by the formation of syn-ore carbonates, together with the consumption of S due to the precipitation of pyrite and arsenopyrite in the second stage, resulted in the decrease of Au, Pb, Zn, and Cu solubility in aqueous fluids. This would have led to the coprecipitation of native gold with galena, sphalerite, and chalcopyrite, forming the general small-scale but commonly occurring native gold−polysulfide veins in the hydrothermal gold deposits. Consequently, both pre- and syn-ore carbonates in the Jinshan deposit were genetically associated with efficient Au-polymetallic deposition through distinct mechanisms. Pre-ore carbonates caused the large-scale bleaching of the host rocks, while syn-ore carbonates were closely related to native gold−polysulfides, and they can both be used as exploration indicators for the Jinshan deposit and other similar hydrothermal gold deposits worldwide.

Numerical Study of Gangue Slurry Deposition Behavior in Pipelines Considering Viscosity Change

Pipeline conveying is a crucial method for realizing gangue slurry filling. In order to avoid the blockage of gangue slurry in pipeline conveying, it is necessary to clarify the deposition behavior of gangue particles in the pipeline. This paper analyzes coal gangue’s microstructure and mineral composition in the Zhaozhuang No. 2 coal mine through electron microscope scanning and X-ray diffraction tests. We studied the viscosity characteristics of gangue slurry at different mass concentrations and particle sizes and analyzed the change rule of viscosity of gangue slurry with time. Based on determining the nature of the slurry material, a simulation analysis of the deposition behavior of the gangue slurry in a pipeline was carried out using the coupled fluid dynamics–discrete element (CFD-DEM) method. The results show that gangue slurry with a particle size larger than 1.0 mm is likely to lead to the blockage of the pipeline. A small increase in viscosity will promote a uniform distribution of particles inside the pipeline. The deposition behavior of particles is jointly influenced by gravity, fluid interaction force, inter-particle force, and the interaction between particles and the pipeline surface. The research results can be used as a reference for the design and study of gangue slurry grouting systems.

Improving the technical device for washing root-and-tuber crops

BACKGROUND: Achievements of agrarian science ensure the competitive development of agricultural production. The key place in solving the problems of which is occupied by technologies and machines of the agro-industrial sector. One of the main directions of the functioning of agriculture is animal husbandry, in particular the feeding of livestock and poultry. An increase in the output per each feed unit is facilitated with preparing them for feeding, including washing and chopping root-and-tuber crops as the most important component of the diet of farm animals. Improvement of these technical devices helps to improve the quality indicators of their operation. AIM: Improving the device for washing root-and-tuber crops with the new patent-worthy technical solution. METHODS: Study of the state of the issue on this topic using a literature sources review. Patent search for technical devices for washing root-and-tuber crops. Studying the principle of their operation and design features. Analysis and generalization of the information obtained for the implementation of the new design solution. RESULTS: A study of the state of the issue of preparing root-and-tuber crops for feeding to farm animals, the conducted patent search and analysis of the studied material revealed that the existing devices for washing root-and-tuber crops do not meet the requirements. The main disadvantage is the low quality of the technological process performed. The use of a number of physical phenomena, such as gravity, friction, pressure, the interaction of fluid (air or water) with the material being processed, made it possible to solve the complex technical problem of creating a technical device at a whole new level. CONCLUSIONS: Thus, based on the adopted technical solutions, the device for washing root-and-tuber crops has been improved at the level of patentability, which makes it possible to improve the quality of processing of root-and-tuber crops, including stabilizing the process of their unloading from the device.

Wetting Behavior of Kerogen Surfaces: Insights from Molecular Dynamics.

In this study, the wettability of a kerogen surface, a key component of shale reservoirs, is investigated by using molecular dynamics simulations. Specifically, we examined the impact of droplet size and morphology as well as surface roughness on the water contact angles. The findings highlighted that the contact angle dependency on the droplet size intensifies with increased rigidity of the surface. Conversely, as the surface becomes more flexible and rougher, it gains hydrophilicity. The higher hydrophilicity stems from the ability of water molecules to penetrate the kerogen corrugations and form more hydrogen bonds with heteroatoms, particularly oxygen. Notably, the contact angle of kerogen hovers between 65 and 75°, thereby crossing the transition from an underoil hydrophilic to an underoil hydrophobic state. Consequently, minor alterations in the kerogen nanostructure can dramatically alter the wetting preference between water and oil. This insight is of paramount significance for refining strategies in managing fluid interactions in shale reservoirs such as geological carbon storage or oil extraction.

Evaluation of drying shrinkage effects on the elastic properties of porous sandstones using a modified micromechanical model

SUMMARY The effects of pore fluids on the elastic properties of sedimentary rocks can be broadly categorized into two mechanisms: variations in pore compressibility due to the physical properties of the fluids and alterations in the stiffness of the rock frame resulting from rock–fluid interactions. Particularly, as rock–fluid interactions alter the stiffness of contacts between mineral grains, changes in the fluid properties around grain contacts can induce volumetric deformation of the rock as well as in variations of the associated elastic coefficients. Even though many previous studies have explored the influence of swelling of clay minerals, the relationships between changes in elastic moduli and deformation in rocks, which hardly contain swellable minerals, remain to date enigmatic. In this paper, to evaluate quantitatively these effects, drying rates, strains and ultrasonic velocities of small cylindrical Berea sandstone samples were measured as their water saturation was decreased by evaporative drying. The measurements clearly showed drying shrinkage and drastic increases in shear and compressional moduli for all the samples under an almost fully dried condition. Previous studies considered that the alteration in surface energy of grain minerals between wet and dry states affected the contact stiffness between them. Some of them used micromechanical model, uniting the Digby grain contact model with the effective medium theory, to interpret the changes in elastic moduli observed in the non-swellable sandstones during water adsorption on the grain surface. The conventional micromechanical model assumes that a mineral grain is a pure sphere and that the number of contacts between the grains is one. However, grains in a sedimentary rock are generally not purely spherical, and the contact surface is composed of several adhesive asperities. We therefore modified the conventional model by introducing the curvature radius and the number of asperities per contact surface. The modified model well reproduced the shear moduli under wet conditions using the strain and moduli measured under dry conditions. On the other hand, the predictions of the compressional moduli using the model were partially in agreement with the experimental results. Therefore, we attempted to qualitatively interpret the relationship by combining the model with the viscoelastic effect associated with wave-induced fluid flow. The deformation and changes in the elastic moduli of rocks resulting from multiple pore fluids within them can be better understood by the present combined model.

Numerical simulation of the fluid and flexible rods interaction using a semi-resolved coupling model promoted by anisotropic Gaussian kernel function

Numerical simulation of the fluid and flexible rods interaction using a semi-resolved coupling model promoted by anisotropic Gaussian kernel function

Experimental study of interactions between dual porous particles released side by side during settling

The settling of porous particles is relevant to many fields of research, which is essential for many natural phenomena and industrial processes. However, due to the complex particle–particle and particle–fluid interactions, the mechanism of porous particles settling has not been fully understood yet. In this study, the settling behaviors and interactions of dual porous particles released side by side are experimentally investigated. The Reynolds number varied from 12 to 258, which is within the transition zone. Particle Tracking Velocimetry and Particle Image Velocimetry were utilized to capture the particles' trajectories and velocities and provide insight into the flow fields around the particles, respectively. The influences of particle porosity ɛ, initial spacing between particles l0*, and Reynolds number Re on the settling process are systematically studied. In this study, ɛ varies from 0 to 0.858 and l0* varies from 0 to 5. The experimental results reveal that there was repulsion between porous particles during settling, which was negatively correlated with l0* and ɛ. When ɛ > 0.3 and l0* < 0.5, the magnitude of the repulsion between porous particles is significantly different from that of the solid particles, and thus, the effect of porosity is important. For other cases, the interaction between porous particles is essentially the same as that between solid particles. The repulsion between the two particles is a result of flow fields asymmetry, and this repulsion vanishes when l0* > 5. The settling process can be divided into three stages depending on the repulsion. Compared to solid particles, the interactions between porous particles are weaker. The reason is that the pore reduces the duration of particle interactions in the repulsion phase, which contributes to the particles to rapid approaching to reach the stable phase.

LATE ARCHEAN SHELF-TO-BASIN IRON SHUTTLE CONTRIBUTES TO THE FORMATION OF THE WORLD-CLASS DATAIGOU BANDED IRON FORMATION

Abstract Banded iron formations (BIFs) are among the few chemical sedimentary archives that capture the biogeo-chemical evolution of Fe cycling and the redox evolution of the early Earth. Although biologically recycled continental Fe has been previously proposed to be a significant source of Fe in BIFs deposited from a stratified ocean at the onset of the Great Oxidation Event (GOE; ~2.5–2.2 Ga), constraining Fe sources and pathways in Archean BIFs remains challenging. Here we present major and trace element and Fe-Nd-Cr isotope data for the largest BIF (i.e., Dataigou) in China to test whether a benthic Fe shuttle was operative during deposition of pre-GOE BIFs. The absence of true, shale-normalized Ce anomalies, coupled with unfractionated Cr and positive Fe isotope compositions, suggests that BIF deposition occurred in an anoxic water column under reducing atmospheric conditions, whereas positive Eu anomalies indicate a significant input from a high-temperature hydrothermal source. Based on a significant correlation between initial Nd and Fe isotope data, we suggest that two Fe sources were periodically mixed and resulted in deposition of the Dataigou BIF. Here, we suggest the following sources: (1) hydrothermal fluids from sea-floor systems (low εNd(t) and high δ56Fe), derived from the interaction of fluids with underlying, older continental crust, and (2) a benthic Fe flux (high εNd(t) and low δ56Fe), generated by microbial Fe(III) reduction in coastal sediments during weathering of a nearby depleted landmass. Results presented here confirm, for the first time, that a microbially driven Fe shuttle was operational and supplied Fe on a basin-wide scale in the absence of atmospheric oxygen.

Some remarks on load modeling in nonlinear structural analysis–Statics with large deformations–Consistent treatment of follower load effects and load control

AbstractLoad modeling in nonlinear statics, particularly incorporating large deformations differs significantly from the treatment in linear analysis. As in structural dynamics masses in a gravity field generate the loading, their location, and their modifications within the deformation process must be considered in a nonlinear simulation. A specific view besides loading by masses is on gas and fluid interaction with structures. In addition, load control using specifically designed algorithms is evaluated with respect to realistic applications. Within the load modeling an unavoidable, however side aspect, is the general discussion about the so‐called follower forces and non‐conservative loading. As an example of real‐world applications, the specifics of inflated rubber dams are presented.

Effect of hydrocephalus in an unsteady cerebrospinal fluid influencing diffusivity

The present study proposes a mathematical framework based on in vivo inputs to compare the dynamic interactions of cerebrospinal fluid (CSF) through an asymmetric channel due to hydrocephalus. This study’s primary goal is to determine the significance of diffusivity in cerebrospinal fluid concerning the rate of fluid velocity for the cardiac cycle. The model of governing equations was simulated by applying a suitable number of dimensionless parameters. The dimensionless governing equations are solved through the classical Laplace transformation method. The impacts of numerous variables over velocity, temperature, and concentration are examined. These variables comprise the porosity parameter, resistance parameter, buoyancy force, and Schmidt number. These plots are sketched for the considerable magnitude of these variables through MATLAB software, and the plots are discussed in detail. The present study shows a decent justification for the neurological papers showing an increase in pressure reflects the velocity for an increase in resistance, porosity, and the Schmidt number shows an inverse in diffusivity, as elaborated in the tabular outline. It was justified that rigorous cerebrospinal fluid velocity for hydrocephalus proved more than the result in ref. [1]. That is, according to ref. [1] the velocity of hydrocephalic patient is 10 mm/s; we proved it is more than 10 mm/s using analytical Laplace transform method.

Small-angle X-ray scattering unveils the internal structure of lipid nanoparticles

Lipid nanoparticles own a remarkable potential in nanomedicine, only partially disclosed. While the clinical use of liposomes and cationic lipid-nucleic acid complexes is well-established, liquid lipid nanoparticles (nanoemulsions), solid lipid nanoparticles, and nanostructured lipid carriers have even greater possibilities. However, they face obstacles in being used in clinics due to a lack of understanding about the molecular mechanisms controlling their drug loading and release, interactions with the biological environment (such as the protein corona), and shelf-life stability. To create effective drug delivery carriers and successfully translate bench research to clinical settings, it is crucial to have a thorough understanding of the internal structure of lipid nanoparticles. Through synchrotron small-angle X-ray scattering experiments, we determined the spatial distribution and internal structure of the nanoparticles' lipid, surfactant, and the bound water in them. The nanoparticles themselves have a barrel-like shape that consists of coplanar lipid platelets (specifically cetyl palmitate) that are covered by loosely spaced polysorbate 80 surfactant molecules, whose polar heads retain a large amount of bound water. To reduce the interface cost of bound water with unbound water without stacking, the platelets collapse onto each other. This internal structure challenges the classical core-shell model typically used to describe solid lipid nanoparticles and could play a significant role in drug loading and release, biological fluid interaction, and nanoparticle stability, making our findings valuable for the rational design of lipid-based nanoparticles.

Physics-Embedded Deep Learning to Predict Real-Time Flow Parameters in Complex Thermodynamic Machinery

Flow through complex thermodynamic machinery is intricate, incorporating turbulence, compressibility effects, combustion, and solid–fluid interactions, posing a challenge to classical physics. For example, it is not currently possible to simulate a three-dimensional full-field gas flow through the propulsion of an aircraft. In this study, a new approach is presented for predicting the real-time fluid properties of complex flow. This perspective is obtained from deep learning, but it is significant in that the physical context is embedded within the deep learning architecture. Cases of excessive working states are analyzed to validate the effectiveness of the given architecture, and the results align with the experimental data. This study introduces a new and appealing method for predicting real-time fluid properties using complex thermomechanical systems.

The Role of the Mineralogical Composition on Wettability via Flotation Test and Surface Complexation Modeling (SCM)

Minerals are the chief constituents of rocks and have varied properties, such as the surface area, surface charge, site density, etc. Hence, numerous interactions are bound to occur in a reservoir during rock–fluid (i.e., rock, crude oil and brine) interactions. This study seeks to assess the role of the mineralogical composition in the wettability of sandstone rocks (SRs) and mineral mixture (MM) using both surface complexation modeling (SCM) and a flotation test. From the considered sandstone rocks, both the experimental results and the simulated counterparts revealed that the SRs were preferentially hydrophilic. For the MM, when the mass fraction of the hydrophobic mineral was increased, the affinity of the MM became slightly hydrophobic, and vice versa. For the dominant sandstone reservoir rock minerals with predominantly negatively charged surfaces, negligible oil adsorption took place due to the interfacial repulsive forces at the oil–brine and mineral–brine interfaces. For the MM with low calcite content, the wetting preference was influenced by the mineral with a prominent surface area. Our developed model portrayed that the main mechanism of oil adhesion onto sandstone minerals was divalent cation bridging. Nonetheless, adhesion of carboxylate (>COO−) onto the illite, montmorillonite and calcite sites also took place, with the latter being more pronounced.

Tension between judicial practices and the procedural iter regarding domestic violence judicial cases involving women

Violence within the family is a global problem that addresses with special concern that relapse against women. International guidelines point to professionalized care for women in different areas of public life, including access to justice, promoting the generation of specials data. The objective of the study is to characterize the judicial cases on domestic violence against women and referred to the Legal Clinic of the Finis Terrae University from the Center for Precautionary Measures of the Family Courts of Santiago de Chile, between the years 2017-2021, providing a better knowledge and understanding of the development of this phenomenon, from the judicial process. The methodology used has been quantitative and includes a universe of 553 causes. The results project to the need for fluid interaction between Family Courts and Regional Governments, as well as the importance of complying with legal procedures. Judicial practices require judges and officials of the Family Courts who are educated and attentive to considering timely attention in the various phases of the trial, as part of the guarantee of access to justice.

High-Resolution Simulation of the Near-Field Pollutant Dispersion in a Nuclear Power Plant Community with High-Performance Computing

This study aims to employ numerical simulations to understand the dynamics of wind fields and air pollutant dispersion in the proximity of a nuclear plant, situated within a specified urban environment. By leveraging computational fluid dynamics (CFD) combined with geographical information system (GIS) data, the research comprehensively models atmospheric interactions in terms of wind flow patterns, building-induced pressure variances, and pollutant trajectories. The computational domain extends over an area of 8.8km×8.4km\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$8.8\\,\ extrm{km} \ imes 8.4\\,\ extrm{km}$$\\end{document}, vertically stretching to 0.5 km. The wind and pollutant distribution equations are discretized using the finite volume method, providing detailed insights into fluid interactions with urban topographies. Key findings highlight the profound influences of terrain, urban structures, and wind flow behavior on the dispersion of radioactive aerosols, shedding light on potential risks and safety protocols for nuclear plant environments.

Theoretical and Experimental Investigation of Liquid and Gas Flow Pressure Drop through Different Sections of A Partially Closed Piping system

Multiphase flow is found in various places in nature and practice. However, multiphase flow is prevalent in the petroleum production industry. This phenomenon gives rise to a significant issue of pressure loss within piping systems, resulting in a loss in production. Multiphase flow has been studied for decades; however, with the increase in unconventional engineering methods, there is now a greater need for its study. This study investigates phenomena related to multiphase flow, such as flow regimes and pressure loss produced by friction, pipe orientation, and various fluid phase properties. An experimental system was designed, and different fluid phases were used to represent varying situations in piping systems. The system included sections of horizontal, inclined, and vertical pipe orientations experienced during hydrocarbon migration from the reservoir to the surface. To replicate industry multiphase flow in the experimental system, we used water to represent the oil and compressed air to represent gas. The pressure differences throughout the system were calculated using the Beggs and Brill Correlation, the Lockhart-Martinelli Parameter, and the Chisholm Equation. Experimental pressure differences and the effect of the choke valve positions were also recorded for the different sections of the system while observing the flow regimes produced by multiphase fluid interaction. Through the research methods, we found that most pressure losses occurred in the elbows, and most frictional pressure loss occurred in the vertical 3ft pipe, while the 45° and 90° downhill pipes experienced increased pressure.

Molecular Mechanics of Liquid and Gas Slip Flow

By taking into account the inhomogeneity introduced by the presence of a solid boundary, slip-flow theory extends the range of applicability of the venerable Navier–Stokes description to smaller scales and into the regime where confinement starts to be important. Due to the inherently atomistic nature of solid–fluid interactions at their interface, slip flow can be described, at least in principle, predictively at this level. This review aims to summarize our current understanding of slip flow at the atomistic level in dilute gases and dense liquids. The discussion extends over the similarities and differences between slip in gases and liquids, characterization and measurement of slip by molecular simulation methods, models for predicting slip, and open questions requiring further investigation.