High Effective Viscosity Research Articles

At Least 10-fold Higher Lubricity of Molecularly Thin D2O vs H2O Films at Single-Layer Graphene-Mica Interfaces.

Interfacial water is a widespread lubricant down to the nanometer scale. We investigate the lubricities of molecularly thin H2O and D2O films confined between mica and graphene, via the relaxation of initially applied strain in graphene employing Raman spectroscopy. Surprisingly, the D2O films are at least 1 order of magnitude more lubricant than H2O films, despite the similar bulk viscosities of the two liquids. We propose a mechanism based on the known selective permeation of protons vs deuterons through graphene. Permeated protons and left behind hydroxides may form ion pairs clamping across the graphene sheet and thereby hindering the graphene from sliding on the water layer. This explains the lower lubricity but also the hindering diffusivity of the water layer, which yields a high effective viscosity in accordance with findings in dewetting experiments. Our work elucidates an unexpected effect and provides clues to the behavior of graphene on hydrous surfaces.

Ferro‐elastohydrodynamic lubrication of inclined slider‐bearing

AbstractIn practice, due to bearing load there is a generation of pressure in the lubricant film, which leads elastic deformation on the bounding surfaces and causes variation in the film thickness. As film thickness plays an important role in performance of the slider‐bearing designs; an attempt has been made to study numerical simulation of elastic deformation effect in one‐dimensional inclined slider‐bearing with ferrofluid (FF) lubricant. The modified Reynolds equation is derived using ferrohydrodynamic theory by Shliomis with transverse uniformly strong magnetic field, and continuity equation. Using this equation dimensionless load‐carrying capacity () is studied for different parameters. The results show the better performance of for lower convergence ratio and higher effective viscosity. However, elastic deformation has no effect on . Some comparisons are also made with the previous literature.

Phononic crystal as a homogeneous viscous metamaterial

At low frequencies, a phononic crystal behaves like a homogeneous medium. Different variants of homogenization technique have been recently proposed to calculate the effective elastic parameters of periodic medium. Here, we develop a homogenization theory for a phononic crystal of solid rods in a viscous fluid. Using the plane wave expansion method, we derive analytical formula for the decay coefficient of low frequency sound propagating in a 2D Bravais lattice with arbitrary unit cell. It is shown that due to the formation of a viscous boundary layer around each cylinder, the losses are enhanced by two to four orders of magnitude as compared to the losses in the free fluid. This enhancement depends on the filling fraction of solid rod and it becomes very strong for almost touching scatterers when sound propagates through narrow slits between the neighbouring rods. Also, the decay coefficient in a phononic crystal scales with frequency as ω2, unlike scaling √ω known for free viscous fluid. The enhanced viscous losses are associated with high effective viscosity of phononic crystal. Like other effective parameters the effective viscosity exhibits strong anisotropy, if the unit cell is asymmetric. The proposed theory can be used for evaluation of efficiency of acoustic devices based on phononic crystals. [This study is supported by NSF Grant No. 1741677.]

Development of methods for evaluation of lubrication properties of hydraulic aviation oils

A method for evaluation of the lubricating and rheological properties of hydraulic oils in tribological contacts has been developed, which consists in online studying samples of commercial batches of oils on a software and hardware complex with visual evaluation of the kinetics of changes in the main tribological indicators of friction contact. Using a roller analogy, the operation of gears in the conditions of rolling with 30% sliding is simulated. Samples of AMG-10 oil from two producers are analyzed. It is established that with increasing temperature of lubricant for Sample 2 (“Kvalitet-Avia” AMG-10), a long-term restoration of protective boundary films of oil is observed and the period of their formation increases by 2.5 times, causing the implementation of a semidry mode of lubrication at start-up. The total thickness of the lubricating layer is 1.27 times less as compared with Sample 1 ("Bora B" AMG-10 oil), regardless of the lubricant temperature. Also, the rheological properties of the oils have been determined. Sample 1 exhibits low shear stresses at the level of 9.4 MPa and high effective viscosity, 4249 and 5039 Pa·s, at a volumetric oil temperature of 20 and 100 ºС, respectively. For Sample 2, with increasing oil temperature to 100 ºC shear stress increases by 1.15 times and the effective viscosity in contact decreases by 1.53 times. Additives present in Sample 1 are characterized by more effective antiwear properties and thus increase the wear resistance of contact surfaces in the conditions of rolling with sliding thanks to strengthening of the surface metal layers during operation, while Sample 2 undergoes strengthening-softening processes which reduce the wear resistance of friction pairs

Composition of the Sub‐Cratonic Mantle of the Guiana Shield Inferred From Diamond‐Hosted Inclusions

AbstractThe composition of diamond‐hosted inclusions provides insight into the character of the sub‐cratonic lithosphere of the Guiana Shield. Guyana's Paleoproterozoic diamonds preserve an inclusion suite comprised of forsterite (Fo ∼89.3–91.8), enstatite, chromite, and Cr‐pyrope. Raman thermobarometry of entrapped olivine and pyrope inclusions indicate entrapment pressures of ∼5.3–7.0 GPa. Unpolarized Fourier transform infrared spectroscopic measurements of forsterite and enstatite inclusions produce low absorbances from OH. Using established calibrations, those absorbances indicate forsterite and enstatite contain median values of 26 ± 14 and 14 ± 18 ppm H2O, respectively, and suggest a high effective viscosity of 1023.7 ± 2.1 Pa∙s for the lithospheric mantle. When combined with inclusion thermobarometry, diamond residence temperatures suggest paleo‐geotherms ranging from 35 to 40 mW m−2. Low‐to‐moderate Fe2O3 content (1.9 ± 0.8 wt.%) and low oxygen fugacity (log ƒO2 (ΔFMQ) −1.6 ± 1.1) determined from chromite inclusions indicate crystallization in reducing conditions. Forsterite and chromite inclusions retain evidence for metasomatic alteration, including Mn‐enrichment in forsterite and chromite rich in Zn. These characteristics indicate that the sub‐cratonic lithosphere of the Guiana Shield experienced episodes of partial melting and fluid‐driven metasomatism of dry, strongly viscous, and moderately depleted garnet‐spinel harzburgite. The Guiana Shield has been relatively stable since the Paleoproterozoic, meaning diamond inclusions may also provide the best means for understanding current conditions in the region's lithospheric mantle.

Evaluation of operational properties of aviation oils by tribological parameters

The quality of aviation oils was evaluated online on the basis of their lubricating, antifriction, rheological and antiwear properties in the friction contact. The use of the software and hardware complex for evaluation of operational characteristics of triboelements is offered. Approbation of the proposed methodology was performed on aviation oils SM-9. The increase in antifriction properties of the “Bora B” SM-9 oil was established to be due to the formation of limiting adsorption layers of lubricant on friction-activated contact surfaces, which are characterized by low shear stresses of the lubricant, and their structuring provides high effective viscosity in the contact at a level of 5142 Pa.s. It was revealed that at start-up the lubricant temperature is 20 0С and the mixed lubrication mode prevails, but with increasing the lubricant temperature to 100 0С the elastic-hydrodynamic (contact-hydrodynamic) lubrication mode dominates, then at maximum rotation speed of friction pairs the hydrodynamic lubrication mode dominates, regardless of oil temperature, which indicates the effective separation of the contact surfaces due to the formation of a lubricating layer between them. Analysis of the specific work of friction in the friction contact showed that the instability of this parameter evidences to intensification of destructive processes in the near-surface layers of metal and reduction in its wear resistance. The decrease in wear resistance of the lagging surface in the conditions of rolling with sliding for all types of investigated oils is due to the different directions of the friction force vector in the contact. In the course of operation of friction pairs in nonstationary conditions, the softening of the surface metal layers occurs, which has a positive effect on the tribological processes in the contact. The practical significance of the work consists in developing a methodology of analysis of lubricants, which makes it possible to more accurately evaluate their performance and provide recommendations for the choice of lubricant for specific friction units.

Characterisation and optimisation of foams for varicose vein sclerotherapy.

Foam sclerotherapy is the process of using an aqueous foam to deliver surfactant to a varicose vein to damage vein wall endothelial cells, causing the vein to spasm, collapse and ultimately be re-absorbed into the body. Aqueous foams are complex fluids that can exhibit a significant yield stress and high effective viscosity which depend on their composition, particularly the bubble size and liquid fraction. To characterise the properties of foams used for varicose vein sclerotherapy and determine their effectiveness in the displacement of blood during sclerotherapy. Foams are modelled as yield stress fluids and their flow profiles in a model vein are predicted. Values of the yield stress are determined from experimental data for three different foams using the Sauter mean of the bubble size distribution. Along with the measured liquid fraction of the foams, this information is collected into a Bingham number which entirely characterises the process of sclerotherapy. Polydispersity in bubble size has a strong effect on the yield stress of a foam and the Sauter mean of the size distribution better captures the effects of a few large bubbles. Reducing the polydispersity increases the yield stress, and a higher yield stress results in a larger plug region moving along the vein, which is more effective in displacing blood. The width of the plug region is proportional to the Bingham number, which also has a quadratic dependence on the liquid fraction of the foam. Assuming typical values for the rate of injection of a foam, we predict that for a vein of diameter 5mm, the most effective foams have low liquid fraction, a narrow size distribution, and a Bingham number B ≈4.5. The Sauter mean radius provides the most appropriate measure of the bubble size for sclerotherapy and the Bingham number then provides a simple measure of the efficacy of foam sclerotherapy in a vein of a given size, and explains the ability of different foams to remove varicose veins. Foams containing small bubbles, with a narrow size distribution, and a low liquid fraction are beneficial for sclerotherapy.

Effect of water on the rheology of the lithospheric mantle in young extensional basin systems as shown by xenoliths from the Carpathian-Pannonian region

Incorporation of hydrogen as structural hydroxyl (commonly referred to as water) in nominally anhydrous mantle minerals is known for the ‘hydrolytic weakening’ effect, which decreases the strength and electrical resistivity of the rock. Recent models have provided means of calculating rheological properties from geochemical data of upper mantle xenoliths. In the Carpathian-Pannonian region, upper mantle xenoliths can be found on the surface at five locations, both at marginal and central regions of the basin system. In this study we present a comprehensive overview of water contents in these xenoliths, including previously lacking data from two outcrops (Füzes-tó and Tihany) from the Bakony-Balaton Highland Volcanic Field for the first time. The Tihany xenoliths have significantly higher water contents (< 1–5, 116–353 and 327–1394 ppm in olivine, orthopyroxene and clinopyroxene, respectively) than the Füzes-tó xenoliths (0–2.7, 6.2–114 and 3.1–213 ppm in olivine, orthopyroxene and clinopyroxene, respectively). This can be explained with the older eruption age of their host basalt and greater depth of origin, as they likely represent an asthenospheric layer that became part of the lower lithosphere during thermal relaxation. In contrast, the Füzes-tó xenoliths represent a lot dryer mantle portion and are assumed to have been more affected by decompression-induced water loss resulting from decreased water activity during the extension. In general, the marginal xenolith locations of the Carpathian-Pannonian region, associated to prior supra-subduction environment, contain more water than xenoliths from central locations (with the exception of Tihany locality) which were significantly affected by extension-related lithospheric thinning. To reveal the differences in rheology inferred from the different water contents, we calculated effective viscosities and electrical resistivities for the xenoliths of the Bakony-Balaton Highland and other locationss in the Carpathian-Pannonian region using previously published data for input. Based on the results, the central locations have higher effective viscosities (1.4∙10 20 –2.2∙10 21 Pa s) and electrical resistivities (48–913 Ωm) compared to the marginal locations (9.3∙10 19 –6.8∙10 20 Pa s and 36–182 Ωm, respectively), suggesting that the lithospheric mantle is more rigid in the former than in the latter areas. This may be a common feature for extensional basins, as the extension leads to the ‘drying’ of the upper mantle, whereas subduction zones keep hydrating their overlying mantle wedge. However, for more accurate estimations, other factors such as regional differences in strain rate or the potential presence of melts or fluids in the mantle need to be considered as well. • Water lowers effective viscosity and electrical resistivity in mantle xenoliths • Water contents of xenoliths from different tectonic environments were compared • Central regions of the back-arc basin are drier compared to marginal areas • Rheological differences are present in distinct parts of extension-subduction systems • Decompression related water loss results in strengthening of the lithosphere

Sudden contraction effects in nanochannel cross section on the rarefied gas flow characteristics: LBM analysis

This mesoscopic investigation aims to study the rarefied gas flow inside a contracting nanochannel in the slip and transitional regimes by two relaxation time lattice Boltzmann method. Bosanquet-type effective viscosity and distribution functions correction at the corner points are used to enhance the precision of slippage velocity on the walls. The boundary conditions at the entrance and exit sections of the nanochannel are assumed nonequilibrium-equilibrium distribution functions. The bounce back-specular reflection boundary conditions are considered for the wall exteriors. It is found that both momentum and rarefaction play essential roles concerning the separation phenomena in nanochannel flow. The higher outlet Knudsen number possesses the higher effective viscosity and shear stress, while the vortices become smaller and tend to disappear at higher Knudsen numbers. The results of the direct simulation Monte Carlo method have been utilized to validate the present numerical prediction, and an outstanding agreement between the results is shown.

Flow systems of the Earth’s viscous subsurface: A complement to groundwater flow systems

Assessment of the long term possibilities and risks related to geological storage requires insight in the deep groundwater flow systems. The objective of this paper is to show the relevance of the deep creep flow of the earth’s viscous upper mantle and crust as a complement to the groundwater flow. The paper presents an approach based on Fourier decomposition of the topography. The creep flow equations are solved analytically, which results in simple indices like penetration depth and relaxation time characterizing the gravity-driven creep flow. Thanks to the very high effective viscosity of the Earth’s subsurface a Darcy-like equation is obtained in which the ‘creep conductivity’ is Fourier mode dependent, which allows for simple comparison with the hydraulic conductivity for groundwater flow. Order of magnitude calculations indicate that for horizontal length scales of 100–1000 km the subsurface creep velocities are 0.3–30 mm/year, respectively, which shows that creep velocities in the deep subsurface are significant with respect to deep groundwater velocities.

Interfacial Interactions During InSitu Polymer Imbibition in Nanopores.

Using insitu nanodielectric spectroscopy we demonstrate that the imbibition kinetics of cis-1,4-polyisoprene in native alumina nanopores proceeds in two time regimes both with higher effective viscosity than bulk. This finding is discussed by a microscopic picture that considers the competition from an increasing number of chains entering the pores and a decreasing number of fluctuating chain ends. The latter is a direct manifestation of increasing adsorption sites during flow. At the same time, the longest normal mode is somewhat longer than in bulk. This could reflect an increasing density of topological constraints of chains entering the pores with the longer loops formed by other chains.

Viscous deformation as a measure of heat work during coal ash fusibility testing

Coal ash fusibility is important in evaluating coal quality and managing coal ash in boilers and gasifiers. Ash fusibility test (AFT) data constitute the basis for many ash and slag management models. Coal ash is a mixture of inorganic compounds derived from sedimentary minerals. As is the case for the bending of pyrometric cones used to control the firing of traditional ceramics, the deformation of coal ash cones is a measure of heat work and not temperature. Heat work, the combined effect of time and temperature, is measured by cone deformation that results from the integration of viscous strain over time. The effective viscosity of 4726 coal ash samples from the U.S. Geological Survey Coal Quality (COALQUAL) database were evaluated at their AFT critical temperatures and found to be lower than the working range of glass, which is consistent with the heat work interpretation of AFT critical temperatures. Thermophysical model data also showed strong positive linear correlations between AFT critical temperatures and the liquidus temperature, as was also the case for pyrometric cones, but not with their solidus temperatures. The finding provides a thermophysical basis for AFT models based on composition while also explaining the spurious correlation between the critical viscosity temperature (TCV) in coal ash slags and AFT critical temperatures. Silicate liquid immiscibility and phase inversion between iron-rich and iron-poor phases results in a sharp change in the effective viscosity of the slag emulsion. High effective viscosities magnify the effect of heating rate variability on AFT critical temperature measurements.

Effects of ROP on Selected Foam Rheological Properties in Vertical Wells

Foam drilling is one of the different techniques of underbalanced drilling which is to intentionally design the proper compressible fluid as drilling mud. The main characteristics of the foam fluids are its wide range of low densities which are generally from 1 to 5 ppg; and its high effective viscosities which are superior to those of both constituents; liquid and gas. Literature reported case stories of foam drilling in most challenging formations with excessive and complete losses due to reservoir depletion, fractured strata, unconsolidated beds etc. For good cuttings removal and desired hole cleaning, the technique of foam drilling relies upon foam high effective viscosity and annular mixture velocity. To guarantee adequate hole cleaning in foam drilling, factors affecting these two parameters must be carefully monitored and controlled during the entire hole sections. As foam rheological properties are among the most affecting parameters for hole cleaning, their detailed studies are not considered exaggerated. Carrying out foam drilling in producing formations results in annular foam rheological properties much different than those in the string due to the intrusion of formation cuttings and fluids into the annular mud stream. Therefore, detailed analysis of different parameters affecting on the annular foam rheology is crucial for optimum foam drilling. Rate of penetration (ROP) is a determinant parameter for drilling economy, but might also be one of the main causes for the changes of the annular rheology of foam. In this paper, we developed a recent program using VISUAL BASIC for a hydraulic model of foam drilling in vertical wells to investigate the influence of ROP on selected foam rheological properties. For the particular conditions in the Appendix Table of this paper, foam annular velocity, quality, density, power index, Reynolds number and cuttings concentration all increase proportionally with the increase of ROP, whereas, annular surface pressure, effective viscosity, consistency index and friction factor all decrease inversely with the ROP increase.

Dynamical Gaseous Rings in Global Simulations of Protoplanetary Disk Formation

Abstract Global numerical simulations of protoplanetary disk formation and evolution were conducted in the thin-disk limit, where the model included a magnetically layered disk structure, a self-consistent treatment for the infall from cloud core, and the smallest possible inner computational boundary. We compared the evolution of a layered disk with a fully magnetically active disk. We also studied how the evolution depends on the parameters of the layered disk model—the MRI triggering temperature and active layer thickness—as well as the mass of the prestellar cloud core. With the canonical values of parameters a dead zone formed within the inner ≈15 au region of the magnetically layered disk. The dead zone was not a uniform structure, and long-lived, axisymmetric, gaseous rings ubiquitously formed within this region owing to the action of viscous torques. The rings showed a remarkable contrast in the disk environment as compared to a fully magnetically active disk and were characterized by high surface density and low effective viscosity. Multiple gaseous rings could form simultaneously in the dead zone region, which were highly dynamical and showed complex, time-dependent behavior such as inward migration, vortices, gravitational instability, and large-scale spiral waves. An increase in MRI triggering temperature had only marginal effects, while changes in active layer thickness and the initial cloud core mass had significant effects on the structure and evolution of the inner disk. Dust with large fragmentation barrier could be trapped in the rings, which may play a key role in planet formation.

Deformation in the mantle wedge associated with Laramide flat‐slab subduction

AbstractLaramide crustal deformation in the Rocky Mountains of the west‐central United States is often considered to relate to a narrow segment of shallow subduction of the Farallon slab, but there is no consensus as to how deformation along the slab‐mantle lithosphere interface was accommodated. Here we investigate deformation in mantle rocks associated with hydration and shear above the flat‐slab at its contact with the base of the North American plate. The rocks we focus on are deformed, hydrated, ultramafic inclusions hosted within diatremes of the Navajo Volcanic Field in the central Colorado Plateau that erupted during the waning stages of the Laramide orogeny. We document a range of deformation textures, including granular peridotites, porphyroclastic peridotites, mylonites, and cataclasites, which we interpret to reflect different proximities to a slab‐mantle‐interface shear zone. Mineral assemblages and chemistries constrain deformation to hydrous conditions in the temperature range ∼550–750°C. Despite the presence of hydrous phyllosilicates in modal percentages of up to 30%, deformation was dominated by dislocation creep in olivine. The mylonites exhibit an uncommon lattice preferred orientation (LPO) in olivine, known as B‐type LPO in which the a‐axes are aligned perpendicular to the flow direction. The low temperature, hydrated setting in which these fabrics formed is consistent with laboratory experiments that indicate B‐type LPOs form under conditions of high stress and high water contents; furthermore, the mantle wedge context of these LPOs is consistent with observations of trench‐parallel anisotropy in the mantle wedge above many modern subduction zones. Differential stress magnitudes in the mylonitic rocks estimated using paleopiezometry range from 290 to 444 MPa, and calculated effective viscosities using a wet olivine flow law are on the order of 1019−1023 Pa s. The high stress magnitudes, high effective viscosities, and high strains recorded in these rocks are consistent with models that invoke significant basal shear tractions as contributing to Laramide uplift and contraction in the continental interior.

An efficient non‐newtonian fluid‐flow simulator for variable aperture fractures

AbstractMany natural and industrial applications involve non‐Newtonian fluids w­ith high effective viscosity ratios flowing between surfaces with spatial variations in aperture. In particular, hydraulic fracturing operations often require pumping sequences of non‐Newtonian fluids with yield‐stress into a variable‐aperture fracture that initially contains water. Numerical methods for this class of problem must deal robustly with the high aspect ratio of the flow domain and large contrasts in effective viscosity while maintaining interfaces between immiscible phases. We avoid the computational burden of a fully three‐dimensional approach by introducing an aperture‐averaged analytic solution for flow of a Hershel‐Bulkley fluid between two plates. We discuss the incorporation of this analytic solution within a simulator of flow within a fracture with spatial variations in aperture. We minimize numerical diffusion through use of a hybrid Lagrangian‐Eulerian approach that naturally tracks the multiple fluid phases. We demonstrate effectiveness of the numerical method through comparison with analytic results and one‐dimensional finite difference numerical solutions. Benchmarking of the 2‐D model against a 3‐D model reveals both advantages and shortcomings of a through‐aperture averaged method. The two simulations agree on the bulk behaviour of the phases while the 2‐D model is two orders of magnitude more efficient. Comparison between predictions of the models after water injection behind the pad reveals that the 3‐D model predicts non‐uniformity across the fracture aperture. This suggests that while bulk behaviour may be well captured by the 2‐D model, improved accuracy could be obtained by introducing multiple fluid layers within each cell of the model.

Theoretical analysis of cermet splats formation under porous quasi-liquid particle ‘melted binder – suspended ultrafine refractory inclusions’ impacting with substrate

The use of composite powders with particles formed by very hard ultrafine inclusions suspended in a metal/metal alloy binder (WC–Co, Cr3C2–NiCr, TiC–NiCr, etc.) in thermal spray process presents a promising strategy in formation of wear-, abrasive- and corrosion resistant coatings. The high volume content of carbide phase inclusions in the cermet powder particles (50–80%) provides high effective viscosity of the binder melt with high-melting solid inclusions suspended in it. That is why takes place a low value of deformation of quasi-liquid particles “melted binder – suspended solid ultrafine inclusions” impinging onto the substrate or onto previously deposited coating layer. All these explain why plasma-sprayed cermet coatings have a comparatively high porosity at the interfaces between individual splats and at the coating–substrate interface. Theoretical analysis of splat formation from porous cermet particle upon its impingement onto substrate was carried out taking into consideration the key physical parameters (KPPs) of particle–substrate interaction: temperature, velocity and size of cermet particle, substrate temperature, volume concentration of ultrafine solid refractory inclusions uniformly distributed in a liquid metal binder.

Extension of a Suspended Soap Film: A Homogeneous Dilatation Followed by New Film Extraction

Liquid foams are widely used in industry for their high effective viscosity, whose local origin is still unclear. This Letter presents new results on the extension of a suspended soap film, in a configuration mimicking the elementary deformation occurring during foam shearing. We evidence a surprising two-step evolution: the film first extends homogeneously, then its extension stops, and a new thicker film is extracted from the meniscus. The second step is independent of the nature of the surfactant solution, whereas the initial extension is only observed for surfactant solutions with negligible dilatational moduli. We predict this complex behavior using a model based on Frankel's theory and on interface rigidification induced by confinement.

Simulation of Slag Freeze Layer Formation: Part II: Numerical Model

The experiments from Part I with CaCl2-H2O solidification in a differentially heated, square cavity were simulated in two dimensions using a control volume technique in a fixed grid. The test conditions and physical properties of the fluid resulted in Prandtl and Rayleigh numbers in the range of 50 and 2.1 × 108, respectively, and the solidification was observed to be planar with dispersed solid particles. In the mathematical model, temperature-dependent viscosity and density functions were employed. To suppress velocities in the solid phase, various models were tested, and a high effective viscosity was found most appropriate. The results compare well with the experiments in terms of solid layer growth, horizontal and vertical velocities, heat transfer coefficients, and temperature distributions. Hydrodynamic boundary layers on the solidified front and on the hot vertical wall tend to be nonsymmetric, as well on the top and bottom adiabatic walls. The high viscosity value imposed on the two-phase zone affects the velocity profile close to the solid front and modifies the heat transfer rate.

Bouncing behaviors of suspension liquid drops on a superhydrophobic surface

This paper reveals three patterns of bouncing behaviors of suspension drops containing calcium carbonate (CaCO3) powder on a superhydrophobic surface with the aid of a high-speed camera. In transmission electron microscopy (TEM) observation, the particles of CaCO3 are shaped like sticks whose equivalent diameters are about 700 nm. Unlike a pure water drop, dense suspension drops cannot be pinched off at the bounce on the superhydrophobic surface due to a high effective viscosity, whereas the equilibrium contact angle appears to be almost identical in all kinds of droplets.