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The coexistence of density stratification and surface tension alters the dynamic behaviors of two-phase immiscible wake and jet flows in complex interfacial instability modes. Building on the framework established by Schmidt et al. ["Global stability and nonlinear dynamics of wake flows with a two-fluid interface," J. Fluid Mech. 915, A96 (2021)], we conduct a global stability analysis to investigate the effects of surface tension and density ratio on the interfacial instabilities of two-phase planar wake and jet flows. Surface tension, acting counterintuitively as either a stabilizer or destabilizer, enhances the self-sustainability of varicose and sinuous disturbances at low levels, while high surface tension ultimately leads to the stabilization of interfacial disturbances. Additionally, sinuous disturbances, characterized by higher oscillation amplitudes, predominate in dense wakes or wakes with strong shear strengths, where surface tension serves exclusively as a stabilizing factor. In contrast, the varicose pattern in jets prevails over a wider range of Weber numbers, exhibiting relatively higher linear growth rates compared to their sinuous counterparts, especially in lighter jets. The temporal-spatial analysis further provides a theoretical demonstration of these findings by offering views into the complex interplay of these factors. [ABSTRACT FROM AUTHOR]

This work is devoted to a theoretical and numerical study of the dynamics of a two-phase system vapour bubble in equilibrium with its liquid phase under translational vibrations in the absence of gravity. The bubble is initially located in the container centre. The liquid and vapour phases are considered as viscous and incompressible. Analysis focuses on the vibrational conditions used in experiments with the two-phase system SF $_6$ in the MIR space station and with the two-phase system para-Hydrogen (p-H $_2$) under magnetic compensation of Earth's gravity. These conditions correspond to small-amplitude high-frequency vibrations. Under vibrations, additionally to the forced oscillations, an average displacement of the bubble to the wall is observed due to an average vibrational attraction force related to the Bernoulli effect. Vibrational conditions for SF $_6$ correspond to much smaller average vibrational force (weak vibrations) than for p-H $_2$ (strong vibrations). For weak vibrations, the role of the initial vibration phase is crucial. The difference in the behaviour at different initial phases is explained using a simple mechanical model. For strong vibrations, the average displacement to the wall stops when the bubble reaches a quasi-equilibrium position where the resulting average force is zero. At large vibration velocity amplitudes this position is near the wall where the bubble performs only forced oscillations. At moderate vibration velocity amplitudes the bubble average displacement stops at a finite distance from the wall, then large-scale damped oscillations around this position accompanied by forced oscillations are observed. Bubble shape oscillations and the parametric resonance of forced oscillations are also studied. [ABSTRACT FROM AUTHOR]

Aerobreakup of drops is a fundamental two-phase flow problem that is essential to many spray applications. A parametric numerical study was performed by varying the gas stream velocity, focusing on the regime of moderate Weber numbers, in which the drop deforms to a forward bag. When the bag is unstable, it inflates and disintegrates into small droplets. Detailed numerical simulations were conducted using the volume-of-fluid method on an adaptive octree mesh to investigate the aerobreakup dynamics. Grid-refinement studies show that converged three-dimensional simulation results for drop deformation and bag formation are achieved by the refinement level equivalent to 512 cells across the initial drop diameter. To resolve the thin liquid sheet when the bag inflates, the mesh is refined further to 2048 cells across the initial drop diameter. The simulation results for the drop length and radius were validated against previous experiments, and good agreement was achieved. The high-resolution results of drop morphological evolution were used to identify the different phases in the aerobreakup process, and to characterize the distinct flow features and dominant mechanisms in each phase. In the early time, the drop deformation and velocity are independent of the Weber number, and a new internal-flow deformation model, which respects this asymptotic limit, has been developed. The pressure and velocity fields around the drop were shown to better understand the internal flow and interfacial instability that dictate the drop deformation. Finally, the impact of drop deformation on the drop dynamics was discussed. [ABSTRACT FROM AUTHOR]

The effect of the instability of the interface morphology due to mechanical disturbances and acceleration changes (or gravity flutter) on Marangoni convective stability has been confirmed via space experiments. However, compared with the research on Marangoni convection with an axisymmetric liquid bridge, research on the transition and interface flow behavior of Marangoni convection with a non-axisymmetric liquid bridge is not sufficiently deep. Based on the thermal-buoyant capillary convection (TBCC) experiment of the conventional liquid bridge, in this study, the influence of the interfacial energy instability triggered by the gravitational tilt angle (GTA) on the spatiotemporal evolution of the flow pattern and velocity distribution of the thermal-buoyant capillary convection is examined by applying the GTA to form the non-axisymmetric liquid bridge model. The results show that the non-equilibrium change in the interface curvature due to GTA leads to a non-axisymmetric liquid bridge morphology. With increasing GTA, the cell-flow morphology during the development process is restricted, transverse/longitudinal velocity component is suppressed, and velocity peak value position gradually approaches the interface. In the oscillating TBCC stage, the deviation of cell flow vortex cores from the intermediate height intensifies with the increasing GTA, resulting in the expansion of the alternating flow zone in the center. Furthermore, the longitudinal velocity component distribution is transformed into the "two peaks and one valley" morphology ("M"-type) from the original multi-peak morphology. The interfacial energy instability due to the GTA can increase the critical temperature difference of the oscillating TBCC, maintain its stability, and delay the onset of the oscillating flow. Simultaneously, the oscillation frequency of the oscillating TBCC is reduced and the development of the oscillating TBCC is suppressed. [ABSTRACT FROM AUTHOR]

• The phase averaged velocity profiles of the core phase were measured in a viscoelastic displacement flow during interfacial instability. • Measurement of velocity fluctuations and turbulence strengths showed significant value when the elastic Mach number is above 0.5, confirming the presence of elastic turbulence. • Large circulation vortices are observed in the core phase below the interfacial deformation. The velocity profiles in the core of a pure viscoelastic liquid displacing a Newtonian oil in a 500 µm microchannel were measured with micro-particle image velocimetry (µPIV) to investigate the onset of elastic turbulence. During displacement, a film of the displaced phase remains on the channel wall while interfacial instabilities develop upstream of the displacing core. Two displacing phase flow rates were investigated at 0.1 ml/min and 0.2 ml/min, corresponding to elastic Mach numbers, M a , of 0.43 and 0.86 respectively. It was found that the velocity profiles in the streamwise and wall-normal directions are almost symmetric with respect to the centre of the core phase, apart from the case at high M a and at the position of maximum interface deformation. Velocity fluctuations are present for the 0.2 ml/min while they are almost zero for the 0.1 ml/min, indicating the presence of elastic turbulence at large flow rate. Similarly, the calculated turbulence strengths at different directions (which make up the turbulent kinetic energy) and the Reynolds stresses have significant values at 0.2 ml/min but are almost zero at the low flow rate. In both flow rates, a circulation pattern is formed below the interfacial instability. [Display omitted] [ABSTRACT FROM AUTHOR]

The review covers the research on thermocapillary convection caused by the thermal action of laser radiation in single-layer and bilayer liquid systems of capillary thickness. The advantages of using optical radiation are the instantaneous delivery of thermal energy to a place on demand (a bulk phase, interfaces); low radiation power required; concentrating heat flux on a spot of a few micrometers; the production of arbitrary spatial distributions of radiation intensity; and, as a result, corresponding thermal fields at a liquid interface and their fast reconfiguration. Thermocapillary stresses at the liquid interfaces lead to the transfer of the liquid and a change in the shape of the interface, in accordance with the distribution of the light-induced thermal field. Studies concerned with the methods of non-destructive testing of liquid media and solids, which are based on a photothermocapillary signal emitted by a laser-induced concave deformation of a thin layer, are considered. Features of thermocapillary deformation of a liquid–air interface caused by local heating of thin and thick (exceeding the capillary length) layers are demonstrated. A part of the review addresses the results of the study of thermocapillary rupture of films in the heating zone and the application of this effect in semiconductor electronics and high-resolution lithography. The works on the light-induced thermocapillary effect in bilayer (multilayer) liquid systems are analyzed, including early works on image recording liquid layer systems, liquid IR transducers, and nonlinear optical media. [ABSTRACT FROM AUTHOR]

The effect of atomic layer deposition (ALD) growth temperature on the interfacial characteristics of p-GaAs MOS capacitors with ALD HfO2 high-k dielectric using tetrakis(ethylmethyl)amino halfnium precursor is investigated in this study. Using the combination of capacitance-voltage (C-V) and X-ray photoelectron spectroscopy (XPS) measurements, ALD growth temperature is found to play a large role in controlling the reaction between interfacial oxides and precursor and ultimately determining the interface properties. The reduction of surface oxides is observed to be insignificant for ALD at 200 °C, while markedly pronounced for growth at 300 °C. The corresponding C-V characteristics are also shown to be ALD temperature dependent and match well with the XPS results. Thus, proper ALD process is crucial in optimizing the interface quality. [ABSTRACT FROM AUTHOR]

This study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations (PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability (RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field. For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results. [ABSTRACT FROM AUTHOR]

From Lagrangian measurements using the Shake-the-Box technique (Schanz et al. in Exp Fluids 57(5):70, 2016) we investigate the velocity field about a single bubble rising in a thin-gap cell and we discuss it in an Eulerian framework of analysis. The gap thickness is equal to 2.85 mm and the bubble-induced perturbation extends over at least 10 cm in the plane of the cell, so that a very flat volume of observation is required. At first validation of the technique is provided during an emptying of the cell. It allows to fix all methodological parameters to ensure accurate measurements and, indirectly, to measure precisely the gap thickness. Then, the velocity field about a confined high-Reynolds number bubble is investigated. This velocity field is discussed in comparison with a previous description obtained by two-dimensional Particle Image Velocimetry (2D2C-PIV) with volume enlightening of the whole cell (Roig et al. in J Fluid Mech 707:444–466, 2012; Filella et al. in J Fluid Mech 778:60–88, 2015). Velocity is first averaged over the gap and compared to the 2D2C-PIV measurement obtained from tomo-reconstructed and projected frontal images. Then a 3D description of the velocity field is presented. It allows to discuss the quality and limitations of the 2D description of the wake with a velocity field integrated across the cell. In particular, the 3D description obtained from STB shows that the flow becomes mainly parallel to the cell plates at a distance of approximately one bubble diameter and that the wake is organised in slices parallel to the plates moving with their own dynamics that may vary their relative in-plane orientations, but all follow the general exponential viscous law of decay. [ABSTRACT FROM AUTHOR]

Complete energy balance evaluations for interfacial flow require simultaneous coupled estimations of the free surface topography and the flow velocity beneath the surface. We describe here an extension of the tomographic PIV and volumetric LPT technique for this coupled measurement. We applied this optical measurement technique to the study of three-dimensional (3D) flow at the air–water interface during the controlled fall of a droplet. Our original setup made it possible to monitor, in real time, the 3D position of fluorescent tracer particles, both on the surface and in the bulk flow. We overcame the shadow effect due to the presence of waves at the interface by illuminating the flow through the underside of a truncated squared pyramidal water tank. We chose to use a water tank of this shape to ensure that optical access could be established orthogonally through the walls of the tank. Four high-speed cameras were focused on the illuminated volume of the flow through the four lateral sides of the pyramidal water tank. The images of the four cameras were analyzed by 3D Lagrangian particle tracking velocimetry (Schanz et al. 2016). With this technique, we were able to track particles accurately at seeding densities compatible with the thresholds for tomographic PIV and to reduce considerably the number of ghost particles. We then obtained local 3D velocities by interpolating vector volumes from the discrete particles. The energy balance was determined by evaluating interface position and bulk flow velocity. Surface curvature and potential energy were determined from surface topography. The kinetic energy of the flow was derived from the bulk flow velocities. We then compared the energy balance thus obtained with that derived from direct visualization of the impact of the same drop. Our findings demonstrate the ability of this technique to characterize such complex interfacial flows in terms of their energetics. [ABSTRACT FROM AUTHOR]

• A microfluidic evaporator with a photothermal porous layer was designed for continuous sample concentration. • Concentration performance of the evaporator were tested under various operation conditions including light intensity, flow rate and different sample type. • By regulating operation parameters the designed evaporator could reach a maximum concentration factor of 2.9 under continuous working condition with minimum flow/thermal disturbance to the bulk solution. On microfluidic platform, sample concentration plays a crucial role in on-chip detection, analysis and synthesis, etc. Evaporation-induced solvent removal is frequently applied to various application scenarios due to its simplicity and compatibility. However, the enclosed microfluidic channels often hinder the solvent vapor discharge during the evaporation process due to the formation of two-phase flow and interfacial instability. Herein, we propose a novel microfluidic evaporator incorporated with a photothermal porous layer for continuous sample concentration. By absorbing the sample fluid into the porous structure, the evaporator is capable of achieving volumetric heating of the sample fluid thus enhancing the solvent evaporation while the porous network ensured efficient vapor venting. Moreover, the thermal resistance of porous layer shields the heat transfer towards the bulk fluid therefore prevented the sample solution from overheating during the operation process. The results demonstrate the designed microfluidic evaporator exhibits good sample concentration capability under continuous flow conditions. [ABSTRACT FROM AUTHOR]

Experiments are done with separated human blood decelerated at constant rates to determine the maximum deceleration rate while avoiding remixing of the layers, which have different densities and viscosities. The deceleration rate affects both the stability and separation of particles through sedimentation. The velocity at onset of instability for a constant deceleration rate is experimentally determined for a 12‐cm‐diameter disk. Parameters of cell pack thickness, plasma thickness, and total thickness are investigated experimentally, and the only statistically significant parameter to affect stability is rate of deceleration. The data describe a correlation separating regions of stability and instability. To understand stability in decelerating flow of separated blood plasma and cells, the equations of motion are solved for a two‐layer fluid flow with a moving boundary and free surface. Inclusion of non‐Newtonian rheology of blood predicts large discontinuities in the shear rate, which is proposed as the cause of the interfacial instabilities. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1376–1386, 2019 [ABSTRACT FROM AUTHOR]

Abstracts In this work, a wet powder spraying method has been investigated as a facile low cost route to deposit electrode layer on SOFC electrolyte support. A particular focus has been examining the interfacial stability of the deposited layers, and determining the influence of the thickness of the different layers, as well as the ball milling regime used to produce the electrode inks. The developed system consist of an yttria stabilized zirconia electrolyte support, a La 0.6 Sr 0.4 FeO 3 (LSF) cathode, a Sm 0.2 Ce 0.8 O 1.9 (SDC) barrier layer between the electrolyte and the cathode, and LaNi 0.6 Fe 0.4 O 3 (LNF) as a contact layer, for a future integration with the SOFC interconnector. The electrolyte supports (300 μm thickness and 9 mm diameter) supports were prepared by uniaxial pressing, while the deposition of thin barrier layers, cathode and contact layer were carried out by manual spray coating. Highlights • Cathode side symmetric cells have been produced by wet powder spraying. • The effect of the ball milling has been studied and process optimized. • The best EIS results were achieved with thicknesses of 10 μm of LSF and LNF. [ABSTRACT FROM AUTHOR]

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid–liquid contact angle; Duez et al. (Nat. Phys. , vol. 3 (3), 2007, pp. 180–183). Using a rough sphere with a contact angle of $120^{\circ }$ , Aristoff & Bush (J. Fluid Mech. , vol. 619, 2009, pp. 45–78) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasistatic, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: (1) cavity shape also depends on the contact angle; (2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we use alternate scales in defining the Bond, Weber and Froude numbers to predict the cavity shapes and scale pinch-off times for various impacting bodies (e.g., spheres, multidroplet streams and jets) on the same plots, merging the often separated studies of solid–liquid and liquid–liquid impact in the literature. [ABSTRACT FROM AUTHOR]

We discuss two distinct spatial structures of vortex streets. The 'conventional mushroom' structure is commonly discussed in many experimental studies, and the exotic 'separated rows' structure is characterized by a thin layer of irrotational fluid between two rows of vortices. In a two-dimensional soap film channel, we generate the exotic vortex arrangement by using triangular objects. This setting allows us to vary the thickness of boundary layers and their separation distance independently. We find that the separated rows structure appears only when the boundary layer is thinner than 40 % of the separation distance. We also discuss two physical mechanisms of the breakdown of vortex structures. The conventional mushroom structure decays due to the mixing, and the separated rows structure decays because its arrangement is hydrodynamically unstable. [ABSTRACT FROM AUTHOR]

This paper examines two-dimensional liquid curtains ejected at an angle to the horizontal and affected by gravity and surface tension. The flow in the curtain is, generally, sheared. The Froude number based on the injection velocity and the outlet's width is assumed large; as a result, the streamwise scale of the curtain exceeds its thickness. A set of asymptotic equations for such (slender) curtains is derived and its steady solutions are examined. It is shown that, if the surface tension exceeds a certain threshold, the curtain – quite paradoxically – bends upwards, i.e. against gravity. Once the flow reaches the height where its initial supply of kinetic energy can take it, the curtain presumably breaks up and splashes down. [ABSTRACT FROM AUTHOR]

Researches on nonlinear instability of power-law plane sheets have been conducted using the Carreau model as the constitutive model. Combined with asymptotic expansion and long-wave assumption, the governing equations and boundary conditions were manipulated using integral transform. The first-order dimensionless dispersion relation between unstable growth rate and wavenumber was obtained and the second-order interface disturbance amplitude was calculated. By comparison and analysis of components of the second-order interface disturbance amplitude, it was found that the power-law index n (n<1) only had an impact on instability of waves with the fundamental wavelength or one third the fundamental wavelength. The findings show that the Carreau-law rheological parameter Bp has little impact on the second-order disturbance amplitude at the interfaces in a practical situation, while the Reynolds number has a positive effect on the growth rate of the disturbance amplitude for the power-law liquid sheets. Finally, the growth rates obtained by numerical simulation and analytical solution have been compared, and the results showed good agreement in the initial phase of wave evolution. [ABSTRACT FROM AUTHOR]

Slow droplet motion on chemically heterogeneous substrates is considered analytically and numerically. We adopt the long-wave approximation which yields a single partial differential equation for the droplet height in time and space. A matched asymptotic analysis in the limit of nearly circular contact lines and vanishingly small slip lengths yields a reduced model consisting of a set of ordinary differential equations for the evolution of the Fourier harmonics of the contact line. The analytical predictions are found, within the domain of their validity, to be in good agreement with the solutions to the governing partial differential equation. The limitations of the reduced model when the contact line undergoes stronger deformations are partially lifted by proposing a hybrid scheme which couples the results of the asymptotic analysis with the boundary integral method. This approach improves the agreement with the governing partial differential equation, but at a computational cost which is significantly lower compared to that required for the full problem. [ABSTRACT FROM AUTHOR]

Abstract Nickel-rich layered transition metal oxides have been highlighted as advanced cathode materials; however, their poor cycling performance at elevated temperatures is a critical hurdle that limits the expansion of their applications. We propose a novel approach for the development of a chemically induced cathode–electrolyte interphase on cathodes using a lithium tetra(trimethylsilyl) borate as a functional precursor. This precursor contains a silyl-borate functional group that forms the cathode–electrolyte interphase layer via chemical reactions, which mitigates electrolyte decomposition and scavenges fluoride species. The precursor is prepared by a convenient one-step synthesis and it readily forms a nanoscale artificial cathode–electrolyte interphase layer through chemical reactions with cathode material during the mixing process used for the preparation of cathode slurries. Our first-principles calculations reveal a thermodynamically favorable reaction between lithium tetra(trimethylsilyl) borate and the fluoride species. We demonstrate that the artificial cathode–electrolyte interphase layer effectively mitigates electrolyte decomposition and the dissolution of transition metal components, thereby improving the interfacial stability of cathodes. As a result, a cell cycled with lithium tetra(trimethylsilyl) borate-modified cathode material shows comparable cycling retention at room temperature and much improved cycling performance at a high temperature after 100 cycles. Graphical abstract Image 1 Highlights • Artificial CEI layer was formed on Ni-rich NCM cathode by lithium salt, LTB. • CEI precursor, LTB, was synthesized by simple and convenient one-step process. • Chemical reactions of LTB with Ni-rich NCM cathode afforded nanoscale CEI layer. • Chemically-induced CEI layers improved surface stability of NCM cathode. • LTB-modified CEI layers allowed stable cycling performances at high temperature. [ABSTRACT FROM AUTHOR]

Abstract A numerical code has been developed for the simulation of unsteady incompressible interfacial flows with large density ratios, based on discretizing the conservation equations on a rectangular adaptive grid with a graded octree data structure, in which the pressure and velocity components are stored at the cell vertices and edges, respectively. With this arrangement, which is novel for octree grids, node alignment simplifies the Poisson equation discretization at nodes common to cells with different refinement levels (irregular nodes), while the staggered storage of variables avoids the pressure–velocity coupling difficulties associated with collocated grids. Three different discretization approaches at irregular nodes are proposed: second- and first-order schemes, and an efficient scheme based on a linear interpolation from the surrounding nodes. A grid refinement test in two dimensions, and 3D deformation and static bubble tests were carried out to assess the accuracy and efficiency of the proposed discretization methods at irregular nodes, the performance of the different schemes used to solve the level set transport equation and the capability of the numerical code to reduce spurious currents. The results of the tests are discussed and compared with results available in the literature. Finally, the ability of the code to accurately simulate the complex phenomena involved in the impact of a water drop on a free surface is demonstrated by thoroughly comparing numerical and experimental results. Highlights • A numerical code to solve the Navier–Stokes equations for unsteady 3D two-phase flows with large density ratios is presented. • The conservation equations are discretized on an adaptive octree grid with a novel cell vertex-edge variable storage arrangement. • New discretization schemes at irregular nodes, with different degrees of accuracy, efficiency and complexity, are proposed. • The accuracy and efficiency of the results obtained with the proposed methods compare favorably with results of previous works. • The ability of the code to accurately simulate complex interfacial phenomena is demonstrated by comparing with experimental results. [ABSTRACT FROM AUTHOR]

Abstract Failure at the interface between a steel substrate and oxide scale was investigated by semi-analytical and finite element numerical simulations. Two major stress components along the interface, i.e., tensile normal stress at the peak and shear stress at the inflection point of the idealized undulated interface, were calculated and used for the failure analysis. The mechanical properties of the oxide scale and steel substrate were experimentally measured by the indentation and uniaxial tensile tests, respectively. Growth and thermal residual stresses accumulated at the oxide scale during cooling were calculated by a coupled numerical-analytical method, which was experimentally validated by measuring the residual stresses in the oxide scales with different thicknesses. The finite element simulation of a four-point bending test was conducted in order to reproduce uncoiling process during which spallation of oxide scale may occur. From the analysis of the simulation results, the two major stress components turned out to be amplified by the roughness of the interface and the residual stresses generated by the growth stress of oxide scale and the thermal mismatch between the oxide and steel substrate during cooling. In addition, the shear stress proved to be a significant factor for the spallation behavior. The effect of scale thickness on the spallation was discussed by using the concept of failure map based on interfacial fracture energy. [ABSTRACT FROM AUTHOR]

We study progressive gravity waves at the interface between two unbounded fluids of different densities. The main concern is to find almost limiting configurations for the so-called overhanging waves. The latter were first computed by Meiron & Saffman (J. Fluid Mech., vol. 129, 1983, pp. 213-218). By means of the Hopf lemma, we rigorously prove that, if ɵ is the angle between the tangent line to the interfacial curve and the horizontal direction, then -л<ɵ <л. This inequality allows us to put forward a criterion of proximity of the interface to the limiting configuration, namely, the angle лɵлmax must be close to p but may not exceed S. We develop a new numerical method of computing interfacial waves based on the representation of a piecewise-analytic function to be found in such a manner that only the shape of the interface is unknown. All other hydrodynamic quantities can be expressed analytically in terms of functions describing this shape. Using this method, we compute almost limiting configurations of interfacial waves with ∣ɵ∣max > 179:98°. Analysing the results of computations, we introduce two new concepts: an inner crest, and an inner solution near the inner crest. These concepts allow us to make a well-grounded prediction for the shapes of limiting interfacial configurations and confirm Saffman & Yuen's (J. Fluid Mech., vol. 123, 1982, pp. 459-476) conjecture that the waves are geometrically limited. [ABSTRACT FROM AUTHOR]

It is known that in steady-state potential flows, the separation of a gravity-driven free surface from a solid exhibits a number of peculiar characteristics. For example, it can be shown that the fluid must separate from the body so as to form one of three possible in-fluid angles: (i) 180°, (ii) 120° or (iii) an angle such that the surface is locally perpendicular to the direction of gravity. These necessary separation conditions were notably remarked upon by Dagan & Tulin (J. Fluid Mech., vol. 51 (3), 1972, pp. 529-543) in the context of ship hydrodynamics, but they are of crucial importance in many potential-flow applications. It is not particularly well understood why there is such a drastic change in the local separation behaviours when the global flow is altered. The question that motivates this work is the following: outside of a formal balance-of-terms argument, why must cases (i)-(iii) occur and furthermore, what are the connections between them? In this work, we seek to explain the transitions between the three cases in terms of the singularity structure of the associated solutions once they are extended into the complex plane. A numerical scheme is presented for the analytic continuation of a vertical jet (or alternatively a rising bubble). It will be shown that the transition between the three cases can be predicted by observing the coalescence of singularities as the speed of the jet is modified. A scaling law is derived for the coalescence rate of singularities. [ABSTRACT FROM AUTHOR]

The nonlinear evolution of an interface between a perfect conducting liquid and a perfect dielectric gas subject to periodic electrostatic forcing is studied under the long-wave approximation. It is shown that inertial thin films become unstable to finite-wavelength Faraday modes at the onset, prior to the long-wave pillaring instability reported in the lubrication limit. It is further shown that the pillaring-mode instability is subcritical in nature, with the interface approaching either the top or the bottom wall, depending on the liquid--gas holdup. On the other hand, the Faraday modes exhibit subharmonic or harmonic oscillations that nonlinearly saturate to standing waves at low forcing amplitudes. Unlike the pillaring mode, wherein the interface approaches the wall, Faraday modes may exhibit saturated standing waves when the instability is subcritical. At higher forcing amplitudes, the interface may approach either wall, again depending on the liquid--gas holdup. It is also shown that a gravitationally unstable configuration of such thin films, under the long-wave approximation, cannot be stabilized by periodic electrostatic forcing, unlike mechanical Faraday forcing. In this case, it is observed that the interface exhibits oscillatory sliding behaviour, approaching the wall in an 'earthworm-like' motion. [ABSTRACT FROM AUTHOR]

We investigate the onset of three-dimensional hydrothermal waves in a low-capillarynumber liquid layer of arbitrary depth, bounded by a free liquid--gas interface from above and a partial slip, rigid surface from below. A selection of two- and threedimensional hydrothermal waves, longitudinal rolls and longitudinal travelling waves, form the preferred mode of instability, which depends intricately on the magnitude of the basal slip. Partial slip is destabilizing for all modes of instability. Specifically, the minimal Marangoni number required for the onset of instability follows Mm ~ a(β-1 + b)-c for each mode, where a; b; c > 0 and β-1 is the slip parameter. In the limit of free slip, longitudinal travelling waves disappear in favour of longitudinal rolls. With increasing slip, it is common for two-dimensional hydrothermal waves to exchange stability in favour of longitudinal rolls and oblique hydrothermal waves. Two types of oblique hydrothermal waves appear under partial slip, which exchange stability with increasing slip. The oblique mode that is preferred under no slip persists and remains near longitudinal for small slip parameters. [ABSTRACT FROM AUTHOR]

Summary: We present a simple and cost‐effective curvature calculation approach for simulations of interfacial flows on structured and unstructured grids. The interface is defined using volume fractions, and the interface curvature is obtained as a function of the gradients of volume fractions. The gradient computation is based on a recently proposed gradient recovery method that mimicks the least squares approach without the need to solve a system of equations and is quite easy to implement on arbitrary polygonal meshes. The resulting interface curvature is used in a continuum surface force formulation within the framework of a well‐balanced finite‐volume algorithm to simulate multiphase flows dominated by surface tension. We show that the proposed curvature calculation is at least as accurate as some of the existing approaches on unstructured meshes while being straightforward to implement on any mesh topology. Numerical investigations also show that spurious currents in stationary problems that are dependent on the curvature calculation methodology are also acceptably low using the proposed approach. Studies on capillary waves and rising bubbles in viscous flows lend credence to the ability of the proposed method as an inexpensive, robust, and reasonably accurate approach for curvature calculation and numerical simulation of multiphase flows. [ABSTRACT FROM AUTHOR]

We construct a model to investigate the interfacial stability of film boiling, and discover that instability of very thin vapour films and subsequent large interface superheating is only possible if thermocapillary instabilities are present. The model concerns horizontal saturated film boiling, and includes novel features such as non-equilibrium evaporation based on kinetic theory, thermocapillary and vapour thrust stresses and van der Waals interactions. From linear stability analysis applied to this model, we are led to suggest that vapour film collapse depends on a balance between thermocapillary instabilities and vapour thrust stabilization. This yields a purely theoretical prediction of the Leidenfrost temperature. Given that the evaporation coefficient is in the range 0.7-1.0, this model is consistent with the average Leidenfrost temperature of every fluid for which data could be found. With an evaporation coefficient of 0.85, the model can predict the Leidenfrost point within 10% error for every fluid, including cryogens and liquid metals where existing models and correlations fail. [ABSTRACT FROM AUTHOR]

The complexity associated with droplets spreading on surfaces has attracted significant interest for several decades. Sustained activity results from the many natural and manufactured systems that are reliant on droplet-substrate interactions and spreading. Interfacial shear rheology and its influence on the dynamics of droplet spreading has to date received little attention. In the current study, saponin β-aescin was used as an interfacial shear rheology modifier, partitioning at the air-water interface to form a strongly elastic interface (G’/G” ∼ 6) within 1 min aging. The droplet spreading dynamics of Newtonian (water, 5 wt% ethanol, 0.0015 wt% N-dodecyl β -D-glucopyranoside) and non-Newtonian (xanthan gum) fluids were shown to proceed with a time-dependent power-law dependence of ∼0.50 and ∼0.10 (Tanner’s law) in the inertial and viscous regimes of spreading, respectively. However, water droplets stabilized by saponin β-aescin were shown to accelerate droplet spreading in the inertial regime with a depreciating time-dependent power-law of 1.05 and 0.61, eventually exhibiting a power-law dependence of ∼ 0.10 in the viscous regime of spreading. The accelerated rate of spreading is attributed to the potential energy as the interfacial film yields as well as relaxation of the crumpled interfacial film during spreading. Even though the strongly elastic film ruptures to promote droplet spreading, interfacial elasticity is retained enhancing the dampening of droplet oscillations following detachment from the dispensing capillary. [ABSTRACT FROM AUTHOR]

Abstract This article reviewed the current state of knowledge of glass aqueous corrosion mechanism with a focus on the contribution of modern characterization tools. A general consensus on the interaction of glass and aqueous medium was discussed. Particularly, the comparison between diffusion controlled corrosion and the interfacial-dissolution-and-reprecipitation mechanism is presented in order to identify the key issues or unknowns in the glass corrosion community. Electron microscope based techniques, chemical depth profiling techniques, and measurement of metrological properties were reviewed from contemporary studies of glass corrosion. In addition, newly-developed characterization techniques that being used in glass corrosion studies were reviewed and discussed. [ABSTRACT FROM AUTHOR]

The conformal-mapping approach is used to formulate a minimal exactly solvable model for studying the lock-exchange gravity currents in an infinite horizontal channel. The distinctive feature of such flows is a pressure jump which arises at the interface between two incompressible fluids of different densities at once after removing a lock gate. Because of this, the process of intrusion does not fit into Benjamin's scenario but rather is like propagation of two shock waves. Being identical in shape and speed, they move in opposite directions along the upper and lower channel boundaries, reaching a steady state as t → ∞. [ABSTRACT FROM AUTHOR]

While the classical problem of a flat plate impact on a water surface at zero dead-rise angle has been studied for a long time both theoretically and experimentally, it still presents a number of challenges and unsolved questions. Hitherto, the details of the flow field – especially at early times and close to the plate edge, where the classical inviscid theory predicts a singularity in the velocity field and thus in the free surface deflection, so-called ejecta – have not been studied experimentally, which led to mutually contradicting suppositions in the literature. On one hand, it motivated Yakimov’s self-similar scaling near the plate edge. On the other hand, a removal of the singularity was previously suggested with the help of the Kutta–Joukowsky condition at the plate edge, i.e. enforcing the free surface to depart tangentially to the plate. In the present experimental study we were able to overcome challenges with optical access and investigate, for moderate Reynolds (0:5 < Re < 25 000) and Weber (1 < We < 800) numbers, both the flow fields and the free surface dynamics at the early stage of the water impact, when the penetration depth is small compared to the plate size, thus allowing us to compare to the classical water impact theory valid in the short time limit. This, in particular, enabled us to uncover the effects of viscosity and surface tension on the velocity field and ejecta evolution usually neglected in theoretical studies. While we were able to confirm the far-field inviscid and the near-edge Stokes theoretical scalings of the free surface profiles, Yakimov’s scaling of the velocity field proved to be inapplicable and the Kutta–Joukowsky condition not satisfied universally in the studied range of Reynolds and Weber numbers. Since the local near-edge phenomena cannot be considered independently of the complete water impact event, the experiments were also set up to study the entirety of the water impact phenomena under realistic conditions – presence of air phase and finite depth of penetration. This allowed us to obtain insights also into other key aspects of the water impact phenomena such as air entrapment and pocketing at the later stage when the impactor bottoms out. In our experiments the volume of trapped air proved not to decrease necessarily with the impact speed, an effect that has not been reported before. The observed fast initial retraction of the trapped air film along the plate bottom turned out to be a consequence of a negative pressure impulse generated upon the abrupt deceleration of the plate. This abrupt deceleration is also the cause of the subsequent air pocketing. Quantitative measurements are complemented with basic scaling models explaining the nature of both retraction of the trapped air and air pocket formation. [ABSTRACT FROM AUTHOR]

During water entry, a projectile can entrain an air cavity that trails behind it. Most previous studies focus on the formation and pinch-off dynamics of the air cavity, but only a few have investigated the long-term cavity dynamics after pinch-off. In this study, we examine the ripple formation following the pinch-off of an air cavity generated by a cone, with different cone angles and impact velocities. The amplitude and wavelength of these ripples are measured, and the force on the cone is experimentally determined. It was observed that the ripple amplitude and wavelength increase linearly with the cone impact velocity, which is predicted by our acoustic model of the compressible air cavity. In addition, the measured force exhibits distinct amplitudes and wavelengths. By measuring the length of the cavity, the resulting pressure variation was averaged inside the air cavity leading to a theoretical force amplitude, which matched our observations. We noted that the force wavelength also follows the same acoustic model, which agrees very well with the wavelength of the ripples. [ABSTRACT FROM AUTHOR]

A uniform nanometric thin liquid film on a solid substrate can become unstable due to the action of van der Waals (vdW) forces. The instability leads to dewetting of the uniform film and the formation of drops. To minimize the total free energy of the system, these drops coarsen over time until one single drop remains. Here, using a thermodynamically consistent framework, we derive a new model for thin films in partial wetting with a free energy that resembles the Cahn–Hilliard form with a height-dependent surface tension that leads to a generalized disjoining pressure, and revisit the dewetting problem. Using both linear stability analysis and nonlinear simulations we show that the new model predicts a slightly smaller critical instability wavelength and a significantly (up to six-fold) faster growth rate than the classical model in the spinodal regime; this faster growth rate brings the theoretical predictions closer to published experimental observations. During coarsening at intermediate times, the dynamics become self-similar and model-independent; we therefore observe the same scalings in both the classical (with and without thermal noise) and new models. Both models also lead to a mean-field Lifshitz–Slyozov–Wagner (LSW)-type droplet-size distribution at intermediate times for small drop sizes. We, however, observe a skewed drop-size distribution for larger drops in the new model; while the tail of the distribution follows a Smoluchowski equation, it is not associated with a coalescence-dominated coarsening, calling into question the association made in some earlier experiments. Our observations point to the importance of the height dependence of surface tension in the early and late stages of dewetting of nanometric films and motivate new high-resolution experimental observations to guide the development of improved models of interfacial flows at the nanoscale. [ABSTRACT FROM AUTHOR]

In the present work, the effect of W coatings prepared by the magnetron sputtering method on the mechanical performance of the Al matrix composites reinforced with diamond particles (Diamond/Al) has been explored. Since no debonding was observed between the diamond and the Al matrix in the composites with 45 nm and thicker W coatings while serious debonding was found in the composite without W coating, the interfacial bonding between the diamond particles (all the {100} and {111} facets) and the Al matrix has been improved. Further TEM observation indicated that the W coating has been well bonded with the diamond particle and the Al matrix, and no interfacial reaction product has been found. Furthermore, the fracture behaviors of the Diamond/Al composites were also affected by the W coatings. Compared to that of the Diamond/Al composite without W coating, the bending strength and the displacement of the bending failure of the Diamond/Al composites with 45 nm W coating have been improved 24% (from 245 to 304 MPa) and 120% (from 0.28 to 0.62 mm), respectively. Moreover, the summative results from the literatures and the present work indicate that the Diamond/Al composites have higher strength usually demonstrates higher thermal conductivity, which might be related to the interfacial performance of the composites. [ABSTRACT FROM AUTHOR]

We study convergence of a boundary integral method for 3D interfacial flow with surface tension when the fluid velocity is given by Darcy's Law. The method is closely related to a previous method developed and implemented by Ambrose, Siegel, and Tlupova, in which one of the main ideas is the use of an isothermal parameterization of the free surface. We prove convergence by proving consistency and stability, and the main challenge is to demonstrate energy estimates for the growth of errors. These estimates follow the general lines of estimates for continuous problems made by Ambrose and Masmoudi, in which there are good estimates available for the curvature of the free surface. To use this framework, we consider the curvature and the position of the free surface each to be evolving, rather than attempting to determine one of these from the other. We introduce a novel substitution which allows the needed estimates to close. [ABSTRACT FROM AUTHOR]

The microstructure and growth behaviors of interfacial IMCs between the Sn-0.7Cu-xIn (x = 0-5.0 wt%) solder and Cu substrate under solid aging were investigated. Bending test was conducted to evaluate the mechanical properties of Cu/Sn-0.7Cu-xIn/Cu solder joints. The needle-like Cu(Sn,In) IMCs formed at interface instead of CuSn in as-soldered In-containing solder joints. During solid aging, indium addition had little influence on the growth of CuSn IMCs, but strongly suppressed the growth of CuSn IMCs. In Sn-0.7Cu-5.0In/Cu couple, the maximum solubility of indium in CuSn and CuSn was about 4.9 and 3.1 at.% respectively which was independent of aging temperature. The average composition of Cu(Sn,In) and Cu(Sn,In) were given as Cu(Sn,In) and Cu(Sn,In). After indium addition, the diffusion coefficients were found to be lower than that of Sn-0.7Cu/Cu couple and the activation energy for the growth of CuSn increased with the increase of indium content. Doping indium into Sn-0.7Cu solder improved the bending properties of solder joints. Interfacial cracks were suppressed effectively after long time aging with indium addition. [ABSTRACT FROM AUTHOR]

The stability of an accelerating cylindrical blob of a time-varying radius is considered with the goals of understanding the effects of time dependence of the underlying base state on a Rayleigh-Plateau instability as well as of evaluating a contribution due to a lateral acceleration of the blob, treated as a perturbation here. All of the key processes contributing to instability development are dissected, with analytical analyses of the exact incompressible inviscid potential flow formulation. Herein, without invoking the 'frozen' base state assumption, the entire time interval of the evolution of a perturbation is explored, discerning physical mechanisms at each stage of development. It transpires that the stability picture proves to be cardinally different from Rayleigh's standard analysis. [ABSTRACT FROM AUTHOR]

Faltinsen et al. (J. Fluid Mech., vol. 487, 2003, pp. 1-42) (henceforth, Part 1) examined an undamped nonlinear resonant steady-state sloshing in a square-base tank by developing an approximate (asymptotic) Narimanov-Moiseev-type multimodal theory. The focus was on longitudinal and diagonal harmonic tank excitations. Neglecting the linear viscous boundary-layer damping was justified for model tanks with breadths of the order of metres. However, nonlinear sloshing in clean tanks of smaller size (count in centimetres) may be affected by damping in finite depth conditions. Qualitative and quantitative properties of the damped resonant steady-state sloshing in a square-base tank are now studied by using the modal theory from Part 1 equipped with the linear damping terms. The tank harmonically oscillates along an arbitrary horizontal (oblique) direction. An analytical asymptotic steady-state undamped solution is derived and the corresponding response curves are analysed versus the forcing direction. When the tank width = breadth = L ~ 10 cm, the surface tension effect on the free-surface dynamics can be neglected but the linear viscous damping should be included into the Narimanov-Moiseev nonlinear asymptotic modal theory. We analytically show that the steady-state damped sloshing possesses a series of distinguishing features so that, e.g. the square-like standing wave regime fully disappears and becomes replaced by swirling. Typical response curves of the damped steady-state resonant sloshing are studied for the liquid depth-to-width ratio exceeding 0.5. The computational results of the steady-state resonant response amplitudes are in a satisfactory agreement with observations and measurements by Ikeda et al. (J. Fluid Mech., vol. 700, 2012, pp. 304-328), which were conducted with a relatively small laboratory container. [ABSTRACT FROM AUTHOR]

A method is presented for deriving reduced models for fluid flows over highly curved substrates with wider applicability and accuracy than existing models in the literature. This is done by reducing the Navier-Stokes equations to a novel system of boundary layer like equations in a general geometric setting. This is accomplished using a new, relaxed set of scalings that assert only that streamwise variations are "slow". These equations are then solved using the method of weighted residuals, which is demonstrated to be applicable regardless of the geometry selected. A large number of results in the literature can be derived as special cases of our general formulation. A few of the more interesting cases are demonstrated. Finally, the formulation is applied to two thick annular flow systems as well as a conical system in both linear and nonlinear regimes, which traditionally has been considered inaccessible to such reduced models. Comparisons are made with direct numerical simulations of the Stokes equations. The results indicate that reduced models can now be used to model systems involving thick liquid layers. [ABSTRACT FROM AUTHOR]

The study of vortex-ring-induced stratified mixing has long played a key role in understanding externally forced stratified turbulent mixing. While several studies have investigated the dynamical evolution of such a system, this study presents an experimental investigation of the mechanical evolution of these vortex rings, including the stratification-modified three-dimensional instability. The aim of this paper is to understand how vortex rings induce mixing of the density field. We begin with a discussion of the Reynolds and Richardson number dependence of the vortex-ring interaction using two-dimensional particle image velocimetry measurements. Then, through the use of modern imaging techniques, we reconstruct from an experiment the full three-dimensional time-resolved velocity field of a vortex ring interacting with a stratified interface. This work agrees with many of the previous two-dimensional experimental studies, while providing insight into the three-dimensional instabilities of the system. Observations indicate that the three-dimensional instability has a similar wavenumber to that found for the unstratified vortex-ring instability at later times. We determine that the time scale associated with this instability growth has an inverse Richardson number dependence. Thus, the time scale associated with the instability is different from the time scale of interface recovery, possibly explaining the significant drop in mixing efficiency at low Richardson numbers. The structure of the underlying instability is a simple displacement mode of the vorticity field. [ABSTRACT FROM AUTHOR]

Interfacial mass transfer is known to be enhanced for confined bubbles due to the efficiency of the transfer in the thin liquid films between them and the wall. In the present experimental investigation, the mechanisms of gas-liquid mass transfer are studied for isolated bubbles rising at high Reynolds number in a thin gap. A planar laser induced fluorescence (PLIF) technique is applied with a dye the fluorescence of which is quenched by dissolved oxygen. The aim is to measure the interfacial mass fluxes for pure oxygen bubbles of various shapes and paths rising in water at rest. In the wakes of the bubbles, patterns due to the presence of dissolved oxygen are observed on PLIF images. They reveal the contrasted contributions to mass transfer of two different regions of the interface. The flow around a bubble consists of both two thin liquid films between the bubble and the walls of the cell and an external high-Reynolds-number in-plane flow surrounding the bubble. Mass transfer mechanisms associated to both regions are discussed. Measurement of the concentration of dissolved oxygen is a difficult task due to the nonlinear relation between the fluorescence intensity and the concentration in the gap. It is however possible to accurately measure the global mass flux transferred through the bubble interface. It is determined from the fluorescence intensity recorded in the wakes when the oxygen distribution has been made homogeneous through the gap by diffusion. Assuming a reasonable distribution of oxygen concentration through the gap at short time also allows a measurement of the mass fluxes due to the liquid films. A discussion of the results points out the specific physics of mass transfer for bubbles confined between two plates as compared to bubbles free to move in unconfined flows. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2394-2408, 2017 [ABSTRACT FROM AUTHOR]

The dynamics of a jet of an inviscid incompressible liquid spiralling out under the action of centrifugal forces is considered with both gravity and the surface tension taken into account. This problem is of direct relevance to a number of industrial applications, ranging from the spinning disc atomization process to nanofibre formation. The mathematical description of the flow by necessity requires the use of a local curvilinear non-orthogonal coordinate system centred around the jet's baseline, and we present the general formulation of the problem without assuming that the jet is slender. To circumvent the inconvenience inherent in the non-orthogonality of the local coordinate system, the orthonormal Frenet basis is used in parallel with the local non-orthogonal basis, and the equation of motion, with the velocity considered with respect to the local coordinate system, is projected onto the Frenet basis. The variation of the latter along the baseline is then described by the Frenet equations which naturally brings the baseline's curvature and torsion into the equations of motion. This technique allows one to handle different line-based non-orthogonal curvilinear coordinate systems in a straightforward and mathematically transparent way. An analysis of the slender-jet approximation that follows the general formulation shows how a set of ordinary differential equations describing the jet's trajectory can be derived in two cases: We=O(1) and ϵWe=O(1) as ϵ→0, where ϵ is the ratio of characteristic length scales across and along the jet and We is the Weber number. A one-dimensional model for the propagation of nonlinear peristaltic disturbances along the jet is derived in each of these cases. A critical review of the work published on this topic is presented showing where errors typically occur and how to identify and avoid them. [ABSTRACT FROM AUTHOR]

Motivated by the reopening mechanics of strongly collapsed airways, we study the steady propagation of an air finger through a collapsed oil-filled channel with a single compliant wall. In a previous study using fully compliant elastic tubes, a 'pointed' air finger was found to propagate at high speed and low pressure, which, if clinically accessible, offers the potential for rapid reopening of highly collapsed airways with minimal tissue damage (Heap & Juel Phys. Fluids, vol. 20 (8), 2008, 081702). The mechanism underlying the selection of that pointed finger, however, remained unexplained. In this paper, we identify the required selection mechanism by conducting an experimental study in a simpler geometry: a rigid rectangular Hele-Shaw channel with an elastic top boundary. The constitutive behaviour of this elasto-rigid channel is nonlinear and broadly similar to that of an elastic tube, but unlike the tube, the channel's cross-section adopts self-similar shapes from the undeformed state to the point of first near wall contact. The ensuing simplification of the vessel geometry enables the systematic investigation of the reopening dynamics in terms of increasing initial collapse. We find that for low levels of initial collapse, a single centred symmetric finger propagates in the channel and its shape is set by the tip curvature. As the level of collapse increases, the channel cross-section develops a central region of near opposite wall contact, and the finger shape evolves smoothly towards a 'flat-tipped' finger whose geometry is set by the strong depth gradient near the channel walls. We show that the flat-tipped mode of reopening is analogous to the pointed finger observed in tubes. Its propagation is sustained by the vessel's extreme cross-sectional profile at high collapse, while vessel compliance is necessary to stabilise it. A simple scaling argument based on the dissipated power reveals that this reopening mode is preferred at higher propagation speeds when it becomes favourable to displace the elastic channel wall rather than the viscous fluid. [ABSTRACT FROM AUTHOR]

The effect of processing conditions of the 75Li 2 S-25P 2 S 5 (LPS) on the Li/LPS DC electrochemical stability was investigated. LPS was densified by compacting at room temperature, and hot pressed between 130–300 °C, 47 MPa. The relative density (80% for all samples) was not affected by the hot pressing temperature, which was likely due to insufficient bulk diffusion (at the pressure used within the temperature range selected) to promote densification. The highly conductive meta-stable crystalline phase (thio-LiSICON III analog) precipitated from the mother glass when hot pressing between 170 − 250 °C and the low conductivity Li 3 PS 4 phase formed when hot pressing at 300 °C. The Li/LPS DC electrochemical stability was characterized as a function of current density between 0.01–1.0 mA cm −2 . Two phenomena were observed; first, as the current density increased, deviation from Ohmic behavior was observed, manifested in an increase in output potential difference. Second, as the current density was further increased, a drop in cell potential was observed followed by an output potential difference instability; likely consistent with short-circuiting caused by Li metal propagation. The highest critical current density, at which short circuit occurs, resulted when hot pressing at 170 °C, reaching 1.0 mA cm −2 . In general, obtaining LPS glass-ceramic through hot pressing increased the rate at which current can be passed through the cell. It is believed that further atomic/microstructure optimization can improve the critical current density of LPS. [ABSTRACT FROM AUTHOR]

In this paper, the stability of two co-axial immiscible fluids flowing in an annular duct is investigated. The inner layer consists of a shear-thinning fluid, which is surrounded by a Newtonian liquid annulus in the outer layer. A constant pressure gradient is applied to drive the flow in the annular channel. Linear stability analysis is employed to investigate the shear-thinning effect on the Rayleigh-Plateau instability and the interface wave instability. Results show that the Rayleigh-Plateau mode can be enhanced and the topological structures of the marginal stability curve of the Rayleigh-Plateau mode can be significantly changed by the shear-thinning effect. When the shear-thinning effect is strong, a case study shows that the Rayleigh-Plateau instability can be slightly suppressed by the viscosity stratification in the inner layer. The shear-thinning effect has a dual influence on the interface wave instability. It can either enhance or suppress the interface wave instability, depending on the thickness ratio and viscosity ratio between the outer layer and the inner layer. [ABSTRACT FROM AUTHOR]

This study investigated the effectiveness of heat-treated wood particles for improving the physico-mechanical properties and creep performance of wood/recycled-HDPE composites. The results reveal that the composites with heat-treated wood particles had significantly decreased moisture content, water absorption, and thickness swelling, while no improvements of the flexural properties or the wood screw holding strength were observed, except for the internal bond strength. Additionally, creep tests were conducted at a series of elevated temperatures using the time-temperature superposition principle (TTSP), and the TTSP-predicted creep compliance curves fit well with the experimental data. The creep resistance values of composites with heat-treated wood particles were greater than those having untreated wood particles due to the hydrophobic character of the treated wood particles and improved interfacial compatibility between the wood particles and polymer matrix. At a reference temperature of 20 °C, the improvement of creep resistance (ICR) of composites with heat-treated wood particles reached approximately 30% over a 30-year period, and it increased significantly with increasing reference temperature. [ABSTRACT FROM AUTHOR]

In this work, the band gap, interfacial properties and electrical properties of Gd doped ZrO 2 high-k gate dielectric films deposited by solution method have been systematically investigated. Results have shown that Gd doping can increase band gap energy from 5.65 to 5.92 eV and effectively restrain the formation of low-k SiO x interfacial layer between dielectric and Si substrate. Moreover, the conduction band offset is increased from 2.57 to 3.06 eV by Gd doping, which effectively reduces the leakage current density to 1.8 × 10 −6 A/cm 2 . [ABSTRACT FROM AUTHOR]

Two-phase flows are present in various industrial processes in engineering fields ranging from light water reactor engineering to petrochemical engineering. In this paper, we conduct the interfacial force study on a single bubble under both laminar and turbulent flow scenarios. Advanced finite-element based flow solver (PHASTA) with level-set interface tracking method is used to perform the studies. The interface tracking approach is verified and validated by analyzing the interfacial forces, i.e., drag and lift forces, and comparing the results with the experiment-based data and correlations. The sign change of transverse migration direction is observed at Eo = 3.4 which is close to the experimental observations. A set of parametric studies, including relative velocity, bubble deformability and turbulent intensity, are performed to analyze the impact of homogeneous turbulent flow on the drag force. A new drag coefficient closure model is proposed which agrees well with the DNS data considering both laminar and turbulent flow. Those studies can complement the experimental database to obtain improved closure laws for interfacial forces and are important contribution to the multiphase computational fluid dynamics (M-CFD) closure model development. [ABSTRACT FROM AUTHOR]

This work is dedicated to the modeling of gas-liquid flows in pipes. As a first step, a new two-layer model is proposed to deal with the stratified regime. The starting point is the isentropic Euler set of equations for each phase where the classical hydrostatic assumption is made for the liquid. The main difference with the models issued from the classical literature is that the liquid as well as the gas is assumed compressible. In that framework, an averaging process results in a five-equation system where the hydrostatic constraint has been used to define the interfacial pressure. Closure laws for the interfacial velocity and source terms such as mass and momentum transfer are provided following an entropy inequality. The resulting model is hyperbolic with non-conservative terms. Therefore, regarding the homogeneous part of the system, the definition and uniqueness of jump conditions is studied carefully and acquired. The nature of characteristic fields and the corresponding Riemann invariants are also detailed. Thus, one may build analytical solutions for the Riemann problem. In addition, positivity is obtained for heights and densities. The overall derivation deals with gas-liquid flows through rectangular channels, circular pipes with variable cross section and includes vapor-liquid flows. [ABSTRACT FROM AUTHOR]