Influence Of Interfacial Slip Research Articles

Study on the influence of interfacial slip on the lubrication performance of a step slider bearing

Experimental and theoretical studies have been completed in this paper to investigate the interface effect in the lubrication performance of a step slider bearing. Oleophobic fluorine-containing diamond-like carbon (F-DLC) coatings were prepared on the step slider to provide low affinity to lubrication films. With an optical slider bearing test rig, it is revealed that the F-DLC coating presents an increase in the film thickness/load-carrying capacity and a decrease in the coefficient of friction (COF), which is quite different from the common idea that both the load-carrying capacity and the COF are reduced at the same time. Contact angles measurement on the step slider shows that the affinity to the lubricant of the inlet step surface is lower than that of the outlet land, which can be attributed to the rougher surface of the step surface by the laser ablation. Theoretical analyses show that various interfacial slip velocities on the inlet step and the outlet land can generate different change in the load-carrying capacity and the COF. When the step surface presents lower interfacial slip velocity of the film than the land surface, increase in load-carrying capacity and decrease in the COF can be theoretically found to support the experiments finds.

Improved Analytical Method for Interfacial-Slip Control Design of Steel–Concrete Composite Structures

Interfacial performance is quite significant for maintaining the structural performance of steel–concrete composite structures. Quantitative assessment on the interfacial effect is critical. For this reason, theoretical investigation on the interfacial interaction of steel–concrete composites was performed, with the symmetry of the model considered. Influence of interfacial slip on the mechanical properties of the composites was considered. Analytical solutions of the interfacial slip and strain were provided. The accuracy of the predictions from the improved analytical model was validated by comparing them against the results from experimental and numerical studies. The influence of design parameters of the composite members on the interfacial effect was discussed. The proposed analytical model was also employed to assess the effect of the bond developing at the interface between concrete and steel on the deformation exhibited by simple composite structural forms (e.g., beams). Through the analysis, the priority design parameters of the composite structures are determined for controlling the level of interfacial slip in order to achieve optimum bearing capacity. Different to commonly used energy methods, numerical methods and finite element methods, the study provides a simple and straightforward analytical solution for describing the interfacial interaction of composite structures for the first time, which can act as scientific instruction for the interfacial slip control of composite materials and structures.

Electromagnetohydrodynamic flow transport of two layer fluids through a microchannel with interfacial slip at fluid-solid interface

This work investigates an electromagnetohydrodynamic flow of two layer fluids through a microchannel under the influence of interfacial slip at fluid-solid interface. The governing equations of conservation of momentum and potential distribution equations with Debye-Huckel approximation has been simplified analytically. The effects of different parameters like transverse electric field, viscosity ratio, interfacial charge density has been presented graphically. Also this study explored that the effect of Hartmann number and large Hartmann number on the velocity of fluid are almost opposite. These results are valid to the available data. Also it is shown that the interfacial charge density has a crucial role to play with the velocity of a fluid.

Influence of interfacial slip on the suspension rheology of a dilute emulsion of surfactant-laden deformable drops in linear flows

The present study deals with the effect of interfacial slip on the deformation and emulsion rheology of a dilute suspension of droplets in a linear flow. The droplets are laden with surfactants that are bulk-insoluble and get transported only along the interface. An asymptotic approach is adopted for the present analysis in order to tackle the nonlinearity present due to deformation of droplets. The analysis is carried out for two different limiting scenarios, namely, surface diffusion-dominated-surfactant transport and surface convection-dominated surfactant transport. For either of the limiting cases, we look into the droplet dynamics for two commonly encountered bulk flows—uniaxial extensional and simple shear flow. Under the assumption of negligible fluid inertia in either phase, it is shown that slip at the droplet interface significantly affects the surfactant-induced Marangoni stress and hence droplet deformation and emulsion rheology. The presence of interfacial slip not only brings about a decrease in the droplet deformation but also reduces the effective viscosity of the emulsion. The fall in both droplet deformation and effective viscosity is found to be more severe for the limiting case of surface convection-dominated surfactant transport. For the case of an imposed simple shear flow, the normal stress differences generated due to droplet deformation are affected as well due to the presence of interfacial slip.

The influence of interfacial slip on two‐phase flow in rough pores

AbstractThe migration and trapping of supercritical CO2 (scCO2) in geologic carbon storage is strongly dependent on the geometry and wettability of the pore network in the reservoir rock. During displacement, resident fluids may become trapped in the pits of a rough pore surface forming an immiscible two‐phase fluid interface with the invading fluid, allowing apparent slip flow at this interface. We present a two‐phase fluid dynamics model, including interfacial tension, to characterize the impact of mineral surface roughness on this slip flow. We show that the slip flow can be cast in more familiar terms as a contact‐angle (wettability)‐dependent effective permeability to the invading fluid, a nondimensional measurement which relates the interfacial slip to the pore geometry. The analysis shows the surface roughness‐induced slip flow can effectively increase or decrease this effective permeability, depending on the wettability and roughness of the mineral surfaces. Configurations of the pore geometry where interfacial slip has a tangible influence on permeability have been identified. The results suggest that for large roughness features, permeability to CO2 may be enhanced by approximately 30% during drainage, while the permeability to brine during reimbibition may be enhanced or diminished by 60%, depending on the contact angle with the mineral surfaces and degrees of roughness. For smaller roughness features, the changes in permeability through interfacial slip are small. A much larger range of effective permeabilities are suggested for general fluid pairs and contact angles, including occlusion of the pore by the trapped phase.

Slip-driven electroosmotic transport through porous media.

We investigate the slip-driven transport of a Newtonian fluid through porous media under electrical double layer effect. We employ a semianalytical framework to obtain the underlying electrohydrodynamics for different configurations of porous media. We bring out an alteration in flow dynamics, stemming from interplay among the geometrical feature of the models and the interfacial slip as modulated by the electrical forcing. Further, we show the consequent effects of the underlying flow dynamics on the volumetric transport rate through different models. Also, we show the inception of reverse flow in the region close to the wall, resulting from the induced pressure gradient due to the convection of co-ions in the opposite direction to flow and pinpoint its effect of the flow rate variation under the influence of interfacial slip. We believe that the inferences obtained from the present analysis may improve the design of bio-MEMS (microelectromechanical systems) and microfluidic devices, which are used for in-situ bioremediation.

Effect of Conjugate Heat Transfer on Entropy Generation in Slip-Driven Microflow of Power Law Fluids

ABSTRACTWe analyze the entropy generation characteristics in a non-Newtonian microflow under the influence of interfacial slip as modulated by the conjugate transport of heat. We consider power law model to represent the constitutive behavior of the non-Newtonian fluid. In this analysis, we analytically solve the transport equations employing the thermal boundary condition of the third kind at the exterior wall surface accounting for the effect of conjugate heat transfer. We demonstrate that the slip flow–driven alteration in convective transport of heat and its nonlinear interaction with viscous dissipation, as modulated by fluid rheology and conjugate transport of heat, gives rise to a minimum entropy generation rate of the system. We determine the optimum value of the geometrical parameter—that is, the channel wall thickness and the thermophysical parameters, such as the Biot number and Peclet number—leading to a minimum entropy generation rate in the system. The results of this analysis could be of helpful in designing microsystems/devices typically used for electronic cooling, micro-heat pipes, and micro-heat exchangers.

Investigation of the effect of fluid slip on heat transfer in the thin-film region in a micro-channel

A theoretical study was undertaken to check the influence of interfacial slip on evaporation of a thin liquid film in a microfluidic channel. The disjoining pressure and the capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted. The evaporating thin film region is an extended meniscus beyond the apparent contact line at a liquid/solid interface. Thin film evaporation plays a key role in a highly efficient heat pipe. Slip length was found to affect the heat transfer in the microchannel by altering the thin film geometry.

Influence of Interfacial Slip on Mechanical Adhesion of Immiscible Polymers

The impact of shear flow instability of two-layer incompatible viscous fluids on mechanical adhesion is studied in this work by numerical modeling. The interface shape evolution is tracked with the level set method using the alternating distance function vanishing at the interface between the layers. It is found that the unstable simple shear flow leads to formation of viscous fingers producing mechanical anchoring after solidification of the system. The shape and length of the viscous fingers are shown to strongly depend on layer viscosity and thickness ratio as well as on interface boundary conditions. The apparent interfacial slip is modeled by the thin intermediate layer of low viscosity. This is found to result in an acceleration of extension of viscous fingers in comparison to that revealed at stick boundary conditions. These structures should lead to strengthening of anchoring between layers and thus promote mechanical adhesion between immiscible polymers.

Detecting solid–liquid interface properties with mechanical slip modelling for quartz crystal microbalance operating in liquid

Quartz crystal microbalances (QCMs) provide sensitive probes for changes at solid–solid or solid–liquid interfaces. It is essential to obtain a physical insight into the details of the interface loading mechanism to interpret the observed behaviour leading to fresh applications of AT-cut quartz resonators. In this work, a mechanical slip model of the interface between a quartz plate and a viscoelastic liquid is presented to replace the continuous displacement assumption. The electrical impedance of a compounded quartz crystal resonator is expressed as a function of the properties of liquid, and the quartz and the strength of contact attraction between the solid and liquid. The interfacial slip parameter between the solid and liquid, which is defined as the displacement transmission from solid particles to liquid bottom particles, is explicitly calculated from the complex attraction strength between the liquid and solid. Comparisons of the physical slip model with other interfacial modes used in the QCM are presented, including the continuous mode and the transmission mode based on the friction force interface. The explicit expression of the slip parameter is presented, and the influence of interfacial slip on QCM measurements is discussed with numerical results. A detailed physical description of the solid–liquid interfacial is useful for exploring fresh ideas for the use of the QCM in biological industry. A new approach by using the slip parameter measured with QCM is proposed to determine the attraction strength between the particles of a viscous liquid and solid particles. The experimental data in the literatures for a hydrophilic-coated sensor and a hydrophobic-coated sensor are used for the numerical examples. It is found that the imaginary part of the interactive strength of these two types of sensor is almost the same. The real part of the interactive strength contributes significantly to distinguish the different interface conditions for these two types of sensor.

On the Influence of Interfacial Slip on Melt Flow Properties of Polymer Blends

Abstract Absolute minima in delineations of viscosity against composition is studied. The hypothesis that this anomaly may be caused by low friction interfaces is scrutinized. Selected polymethylmethacrylates (copolymers) and polystyrenes are used as model materials. An interfacial (slip) viscosity is formally defined by considering the interfaces as separate layers in a multilayer sample consisting of alternating thin layers of polymer 1 and polymer 2. For such a multilayer the steady state shear viscosity of the blend at constant shear stress may be written: 1/η = Φ1/η1 + Φi/ηi + Φ2/η2, where ηi, ηi, and η2 are the viscosities of polymer 1, the interface and polymer 2, respectively. Φ1, Φi and Φ2 are the corresponding volume fractions. Using this equation ηi, is found from measurements on multilayer samples. ηi is found to be lower by a factor of 10 than the lowest viscosity of the homopolymers. Domain stability of the model system are investigated. The minima in viscosity-composition plots of well disp...