Formation Of Water Film Research Articles

Acclimation of interacting leaf surface traits affects foliar water uptake.

Absorption of water across the surfaces of leaves is an ecologically important aspect of tree physiology. Variation in foliar water uptake capacity depends on environmental conditions when traits associated with the uptake pathway respond to climatic signals. Using a series of experiments, we verify that water enters Sequoia sempervirens (D. Don) Endl. leaves by crossing the cuticle, and show that surface-trait acclimation alters the kinetic parameters of foliar water uptake. Under our experimental conditions, the cuticle was the primary pathway for water entry into the leaf. Exposure to climatic variation may induce surface acclimations, such as increased waxiness, that reduce water-film formation over stomata at the expense of dry-season foliar uptake rates. We found that water uptake is negatively associated with the interaction of leaf-surface wax coverage and stomatal density, and provide an accessible protocol to measure these key traits in Sequoia. Linking absorptive pathways and trait acclimation to physiological performance can provide a foundation for range-wide or genomic investigations of forest interactions with water and a mechanism-centered means to monitor canopy hydraulic parameters over time.

Investigation on combined effect of humidity–temperature on partial discharge through dielectric performance evaluation

The humidity role in the partial discharge (PD) inception mechanism is quite challenging, especially when considering the environmental temperature. Indeed, there is no general rule to explain the humidity effect on the PD phenomenon. In this paper, the PD activity in inter-turn insulation is experimentally investigated for different relative humidity (RH) conditions at three different ambient temperatures, that is, 30°C, 60°C, and 90°C. Partial discharge inception voltage (PDIV) is directly measured through a photomultiplier tube (PMT), whereas the tip-up tests are performed aiming at monitoring both dissipation factor (tanδ) and insulation capacitance (IC). These extra measurements (diagnostic dielectric markers) allow better assessing the insulation status. The adoption of the tip-up test enables the insulation properties measurement. Based on the tip-up tests’ findings, the interfacial polarization process starts at 75% RH under 60°C, while the high conductivity area is already formed at 75% RH when the ambient temperature is 90°C. The water film formation deduced from the tip-up test is then used to explain the trend of PDIV, and the validity is further proved by finite element analysis (FEA).

Unsteady convective flow of a preheated water-in-oil emulsion droplet impinging on a heated wall

This work proposes a mechanism of deformation of an emulsion droplet upon collision with a wall, considering the vortex motion of a liquid inside the droplet. This motion leads to an increase in dissipative energy losses, affects spreading, corona splashing, and droplet relaxation at different liquid and wall temperatures, ranging from 20 °C to 80 °C, and influences the equilibrium shape of the drop during the liquid relaxation. For We = 100–900 and Re = 100–4000, a physical model is presented for the maximum spreading diameter of the emulsion droplet; it takes into account the heating of the boundary viscous layer and the development of temperature gradients along the droplet height, convective mixing of the liquid layers, and translational and vortex flow motion along the radius and height of the droplet. The process of corona splashing of the emulsion droplet has been studied, and the influence of the viscosity gradient due to the intermittent near-wall water film formation on the dynamics of the “corona” has been revealed. These differences led to the formation of an air gap, which in the case of an emulsion drop caused the development of a corona at lower We compared to homogeneous liquids. The duration of the liquid relaxation before capillary wetting was affected by the potential barrier of the contact line of the droplet, which depended on the vortex component of the velocity field as well as on the temperatures of the interacting media. Altering the initial thermal boundary conditions changed the relaxation time up to 60%.

Water accumulation and anti-sliding decay characteristics of freeway pavement at superelevation transitions

To evaluate the water accumulation status at superelevation transitions of the freeway and establish a correlation with wet friction, laboratory tests and theoretical calculation approaches were carried out during water-film formation and sheet flow stages. The influencing factors on water depth and the water depth dependency of friction were analyzed using the self-developed multi-directional adjustment tester. The results indicate that the ponding is severe at flat road sections, adjusting alignment and improving drainage capacity are the key remedies. There is a good correlation between decay characteristics of dynamic friction and the water depth. The wet grip can be explained by the tribology principle and lubrication regimes, which is decomposed into the distinct contributions of tire, pavement, and water. Besides, the water depth threshold was determined. Finally, a prediction model of water depth at superelevation transitions was established based on the hydromechanics analysis. It shows significant correlations with the Gallaway model.

Partial Discharge Investigation Under Humidity Conditions via Dissipation Factor and Insulation Capacitance Tip-Up Test

The humidity role in the partial discharge (PD) inception mechanism is quite complex, and there is no widely accepted theory that can describe the humidity effect on PD. In this article, the PD activity of interturn insulation of electric motor winding is experimentally investigated for different relative humidity (RH) conditions at 30 °C ambient temperature. Since the inception of PD leads to a boost in the dissipation factor (i.e., tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta$ </tex-math></inline-formula> ) and insulation capacitance (IC), tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> and IC tip-up test can be adopted as an indirect measurement of PD. The test campaign is carried out employing twisted pairs as samples, and both tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> and IC are measured under a sinusoidal voltage regime. Apart from being indirectly detected, PD activities are also directly measured through a photomultiplier, while the tip-up test is performed. The adoption of direct PD measurement is to discriminate the PD from other ionization processes (e.g., water film ionization), which cannot be distinguished by indirect measurement. The experimental findings allow stating that the change of PD inception voltage (PDIV) at higher RH is due to the different places of water film formation on the insulation surface, and Paschen’s law combined with finite element analysis is used to interpret the effect of water film on PDIV. In addition, it is verified that the tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> and IC tip-up test is not suitable for indirect measurement of PD in high humidity conditions. In fact, the higher leakage current, due to the water condensation on the insulation surface, influences the tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> and IC measurements causing an increment in their values regardless of the PD inception.

Disentangling factors controlling earthquake-triggered soft-sediment deformation in lakes

In-situ soft sediment deformation structures (SSDS) are commonly used as paleoseismic indicators in marine and lacustrine sedimentary records. Earthquake-related shear can deform sediment in the shallow subsurface through Kelvin-Helmholtz instability. The SSDS related to Kelvin-Helmholtz instability have been used to quantify shaking strength of past earthquakes. However, the relative importance of i) lithology and physical properties, ii) potential basal shear surfaces (e.g. clastic deposits), iii) slope angle, and iv) seismic shaking strength (e.g. peak ground acceleration) for deformation related to Kelvin-Helmholtz instability remains poorly studied. Lake Riñihue (south-central Chile) is chosen as a natural laboratory for disentangling the effect of the aforementioned factors because i) the sediment composition of background sediment varies downcore and ii) volcanogenic clastic deposits are abundant within the sedimentary sequence. A previous study at lake Riñihue identified 25 SSDS intervals induced by historical earthquakes of varying rupture extent in 17 sediment cores taken at slope angles ranging from ~0.2° to ~4.9° (i.e. 16 slope sites and 1 basin site). Our study shows that deformation mostly occurs directly above volcanogenic deposits (i.e. 72 % of SSDS intervals), suggesting that volcanogenic deposits promote earthquake-induced deformation by strain softening, liquefaction or water film formation. Deformation thickness of SSDS increases with higher slope angles (i.e. strong positive correlation). Additionally, deformation thickness commonly corresponds to the stratigraphic depth of the youngest preceding volcanogenic deposit, but for steeper slope angles stratigraphically older volcanogenic deposits can function as basal shear surface. Therefore, we suggest that deformation thickness is primarily regulated by gravitational stress (i.e. slope angle) and secondarily by the stratigraphic depth of volcanogenic deposits. The earthquakes related to strongest shaking caused almost exclusively SSDS with highest deformation degrees (i.e. folds and intraclast breccia) as well as largest spatial extent of SSDS, resulting in highest numbers of related SSDS in the investigated cores. Thinner SSDS have higher deformation degrees at a given shaking strength, as seismically-induced shear energy acts more effectively on thinner deforming sequences. Therefore, we suggest that deformation degree is primarily controlled by shaking strength and secondarily modulated by the thickness of the deforming sequences. We infer that deformation thickness is not a reliable indicator of paleoseismic shaking strength as this relies on many preconditioning factors independent of shaking strength. On the other hand, deformation degree can be a good proxy for shaking strength also in settings with varying lithotypes and intercalated clastic event deposits, provided multiple cores are studied to avoid under- or overestimation of paleoseismic shaking strength.

Aerodynamic performance investigation of an axial flow compressor under water ingestion

This paper presents numerical simulations of the effects of water ingestion in the axial flow compressor. A self-compiled droplet-wall interaction model is used to study the impingement of the droplets and the film fragmenting process on the surfaces of the compressor blades, which also included the splashing effects. The blade profile has been divided into small regions to effectively apply the rough wall model to capture the film-related flow losses, which has shown flow characteristics with better accuracy. The formation of water film, its shedding, the size, and the movement of droplets after film peeling have been investigated using unsteady simulations at different time intervals. The increased loss of characteristics, shortening of the operating range, and change of flow velocity angle were observed with increasing water content. Moreover, the current research work shown that an increase in the amount of water has severe aerodynamic effects that caused the shock waves to move an upstream location with an increase in intensity. A higher blockage is generated in the tip section flow as the amount of the water increased. Tip losses were very dominant as water injection rate increased, resulting an additional energy loss and performance degradation.

The Effective Thermal Conductivity of Unsaturated Porous Media Deduced by Pore-Scale SPH Simulation

The smoothed particle hydrodynamics (SPH) method was employed to simulate the heat transfer process in porous media at the pore scale. The effective thermal conductivity of a porous medium can be predicted through a simulation experiment of SPH. The accuracy of the SPH simulation experiment was verified by comparing the predicted values with reference values for ideal homogeneous media and multiphase layered media. 3D simulation experiments were implemented in granular media generated by the PFC method. Based on the SPH framework, a concise method was proposed to produce unsaturated media by simulating the wetting process in dry media. This approach approximates the formation of liquid bridges and water films on granules. Through simulation experiments, the empirical formula of the variation in thermal conductivity with the degree of saturation was tested. The results showed that the reciprocal of the normalized thermal conductivity and the reciprocal of the saturation are linearly related, which is in line with the empirical formula proposed by Cote and Konrad.

Water/InP(001) from Density Functional Theory.

The interface between water and the In-rich InP(001) surface is studied by density functional theory with water coverage ranging from single molecules to multiple overlayers. Single molecules attach preferably to three-fold coordinated surface In atoms. Water dissociation is energetically favorable but hindered by an energy barrier that decreases with increasing water coverage. There is an attractive interaction between InP adsorbed water molecules that leads to the formation of molecular clusters and complete water films for water-rich preparation conditions. Water films on InP are stabilized by anchoring to surface-bonded hydroxyl groups. With increasing thickness, the water films resemble the structural properties of ice Ih. The oxygen and hydrogen evolution reactions on InP are characterized by overpotentials of the order of 1.7–1.8 and 0.2–0.3 eV, respectively. While the calculated bulk positions of the InP band edges are outside the range of the redox potentials for oxygen and hydrogen evolution within local DFT, the situation is different at the actual interface: Here, the interface dipole lifts the InP valence band maximum above the redox potential for oxygen evolution and favors hydrogen evolution.

Effect of surface topography and wettability on friction properties of CFRPEEK

The good physical and chemical properties of CFRPEEK make it advantageous as a friction pair for water hydraulic components. This paper investigated the effects of surface topography and wettability on the tribological properties of CFRPEEK and 316 L under water lubrication, with emphasis on four topographies of hemispherical pit, conical pit, ellipsoidal pit and wedge-shaped pit. From the experimental results, the ellipsoidal pit CFRPEEK samples exhibited the best tribological properties and better wettability. An interesting phenomenon was found that when the contact angle of the CFRPEEK sample is small, the friction coefficient and the wear scar depth are also small. In conclusion, taking the ellipsoidal pit as the surface topography of the CFRPEEK sample is conducive to improving its wettability, and promote the formation of stable water film, thereby improving its performance, reducing wear and increasing its service life.

Maintaining the PM Removal Efficiency of a Two-Stage ESP With External Ion-Injection Discharge via a Water Film on the Collection Plate and Cleaning of the Ionizer

A two-stage electrostatic precipitator (ESP) with a reduced footprint, external ion-injection discharge, and water film on the collection plate was developed for long-term operation. For optimal particulate matter (PM) removal efficiency, the ionizer of the external ion injection system was fixed at a distance of 5 mm from the bias plate. Under these operating conditions, the 0.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m PM (PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> ) removal efficiency was reduced to approximately 70% due to low migration velocity. The application of an additional collection plate extended the residence time of the charged particles in the electric field, which resulted in a removal efficiency exceeding 95%. However, long-term operation (675 min) of the two-stage ESP with external ion-injected discharge resulted in spark generation due to contamination of the ionizer, and the PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies decreased linearly from 80.4% to 62.2% and 87.7% to 68.2%, respectively. Changing the ionizer to a pin shape with electrical specifications similar to those of carbon fibers resulted in water film formation on the collection plate. The PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies remained at their initial levels for 120 min. The two-stage ESP with external ion-injected discharge operating with a water film is likely suitable for long-term operation in an industrial setting.

Study of hydration of kaolinite and montmorillonite mixture by IR spectroscopy

KGa-1b kaolinite and STx-1b montmorillonite, as well as their mechanical mixture in 1:1 mass ratio, have been experimentally investigated by total reflection IR spectroscopy (IR-ATR) at different moisture modes. The aim of this research was to investigate the spectral features during the formation of water films on the surface of individual minerals, and in mixtures. The analysis of mineral composition of the wetted samples has been carried out by decomposing the experimental spectra into the linear combination of basic spectra of H2O and the minerals used. The obtained dependences of the decomposition coefficients on moisture allow studying the peculiarities of the formation of a water layer on mineral particles, studying the dynamics of moisture redistribution between mineral particles in mixtures, and evaluating the plastic characteristics of clays.

Effects of surface roughness on the kinetic interface-sensitive tracer transport during drainage processes

Porous media surface roughness strongly influences the transport of solutes during drainage due to the formation of thick water films (capillary condensation) on the surface of the porous medium. For interfacially-reacted, water-based solutes, these water films increase both the solute production at the fluid-fluid interface, due to the increased number of fluid-fluid interfaces, and the loss of the solute due to retention in the water films. This study applied a pore-scale, direct numerical simulation with the phase-field method-based continuous solute transport model to simulate the reactive transport of the kinetic interfacial sensitive tracer. The study is implemented during primary drainage in a 2D slit with rough solid walls, where the fractal geometries of the solid surfaces were generated numerically. The moving interfacial area is found to be changing non-monotonically with the root mean square of surface roughness. With increasing root mean square roughness, the average film thickness increases linearly, whereas the film-associated interfacial area per smooth surface area converges to a value slightly larger than one. The retention of the solute mass produced by the moving meniscus in the water film is observed, and this is described by a film-associated mobile mass retention term. An implicit relation between the mobile interfacial area and the solute mass in flowing zones is found. Finally, it is found that the film-associated mobile mass retention term is linearly related to the root mean square roughness.

Optimizing the dosing and trickling of nutrient media for thermophilic biomethanation in a biotrickling filter

Ex-situ biomethanation in a biotrickling filter is being developed as a robust technology for the conversion of CO2 to CH4 using H2 generated from renewable power. The technology uses hydrogenotrophic methanogens in a biofilm as the catalyst and the optimum supply of nutrients in the biofilm is imperative for stable and long-term operation. In this study, essential nutrients for the methanogens in the biotrickling filter were highlighted along with a systemic investigation of the nutrient supply methods. The results showed that ammonium and iron were the critical nutrients with a minimum required concentration of 0.3 g/L and 1.5 mg/L, respectively. Furthermore, thoroughly wetting the biofilm with nutrient media, either using flooding or flushing, was needed to maintain an active biofilm; although, these methods temporarily reduce the conversion for a duration of 18–24 h due to the interpreted formation of a thicker water film.

Synergetic effect of fly ash cenospheres and multi‐walled carbon nanotubes on mechanical and tribological properties of epoxy resin coatings

AbstractThe multiform wear of friction pair components is the main cause of marine equipment failure and epoxy resin (EP) coatings have been widely used in this field. Fly ash cenospheres (FACs) and multi‐walled carbon nanotubes (MWCNTs) were used to reinforce the tribological properties of EP coatings. The synergetic effects of FACs and MWCNTs on the mechanical and tribological properties of EP coatings were studied. Experimental results show that the tensile and flexural properties of FACs‐MWCNTs/EP composites are significantly reinforced. The tribological performance of EP composite coatings under seawater conditions is improved by the synergetic effect of FACs and MWCNTs, especially, the 10 wt.% FACs‐1 wt.% MWCNTs/EP coatings behave the most excellent tribological properties. It indicates that FACs can increase the hardness of EP coatings and provide a smoother surface for the water film formation, which decreases the friction coefficient and wear volume. MWCNTs can increase the elasticity modulus of EP, and act as a rope to prevent EP matrix and FACs from being desquamated.

Effects of flow parameters on thermal performance of an inner-liner anti-icing system with jets impingement heat transfer

The multiple jets impingement heat transfer is widely applied in the wing anti-icing system. It is challenging to apply the similarity criterion to carry out the anti-icing experiments due to the complex flow and heat transfer behavior. In the present study, the full-scale slat model is used to carry out anti-icing experimental researches in a 2 m × 3 m icing wind tunnel of China Aerodynamics Research and Development Center. The effects of icing parameters Liquid Water Content (LWC) and Median Volume Diameter (MVD) and hot air parameters (mass flow rate and temperature) on the thermal performance of an inner-liner anti-icing system with jets impingement heat transfer are studied. The effects of the experimental parameters are analyzed in detail by combining impingement and evaporation heat transfer mechanisms. The impingement hot air mass flow rate dramatically affects the heat transfer performance of the impingement stagnation region within the range of the experimental parameters. The temperature of impingement hot air and that of wing skin are approximately linear correlated. The experimental results show the effects of LWC and MVD on water film formation and runback ice accretion. The formation of water film is analyzed by an analytical method based on the wing skin temperature difference of dry and wet air conditions.

In Situ Synthesis of Graphene Nitride Nanolayers on Glycerol-Lubricated Si3N4 for Superlubricity Applications

The increasing demand for sustainable tribology has accelerated the development of environmentally friendly lubrication solutions such as water or water-related lubricants. Earlier works have reported on water-lubricated sliding of silicon nitride (Si3N4) at high speeds, which can result in a superlow friction (μ < 0.01) owing to the formation of hydrodynamic water films on hydrophilic surface layers. Here, combined boundary-lubrication experiments at low sliding speeds and atomistic simulations reveal an alternative superlubricity mechanism for glycerol-lubricated Si3N4. X-ray photoelectron and time-of-flight secondary ion mass spectrometry performed inside and outside the wear track as well as high-resolution mass spectroscopy of the used lubricant strongly suggest that sub-nanometer-thick graphene nitride layers form at the very top of Si3N4. In the accompanying atomistic simulations, glycerol molecules undergo tribochemical decomposition and react with surface-bound nitrogen atoms to form carbon nitrides. Further shearing promotes the formation of 2D graphene nitrides that passivate the ceramic surfaces and induce a superlow friction under boundary lubrication. Thus, glycerol-lubricated Si3N4 has a high potential for use in green superlubricity enabled by in situ synthesis of disordered graphene nitride species.

Study of the Features of the Formation of Water Films on the Surfaces of Montmorillonite and Kaolinite by Infrared Spectroscopy

Reference samples of kaolinite KGa-1b and montmorillonite STx-1b have been studied by infrared spectroscopy at different humidity. The spectral features reflecting the formation of water layers on the basal surfaces of individual minerals have been studied. The experimental studies have been performed using infrared spectroscopy of disturbed total internal reflection. The composition of wet samples has been analyzed by decomposing the experimental spectra into the spectrum of H2O and used minerals in the air-dry state. The obtained dependences of the coefficients of participation of the basic spectra on humidity have been compared with the results of the measurements in the ultrahigh frequency range and they allow us to study the integral features of the formation of a water layer on mineral particles and to evaluate the plastic characteristics of clays. The anomalous position of the maximum and the half-width of the band of valence vibrations of water at low humidity have been found.

Water evaporation model of a catalyst converter in the context of hybrid electric vehicles energy and pollutants management

The energy and pollutants management of Hybrid Electric Vehicles (HEV) consists in determining at each instant the optimal torque split between the Internal Combustion Engine (ICE) and the Electric Motor (EM). This torque choice aims to minimize both fuel consumption and pollutants emissions. A critical piece of information in this context is the value of the Three-Way Catalyst Converter (3WCC) conversion efficiency. This value is highly dependent on the 3WCC temperature; it is hence of major importance to have an accurate estimation of it. Although the literature is abundant about simple 0D thermal models of 3WCC, it is tempting to implement a more accurate and consequently complex model. In particular, both moisture from the exhaust gases during engine start and from ambient air during cooling phases lead to the formation of a liquid water film on the monolith’s exchange surface, causing a strong temperature plateau during the warm-up phase. The water evaporation causing a delay in the 3WCC temperature increase, it could lead to a serious degradation of the pollutants emissions if not taken into account. This paper proposes hence a 1D thermal model including water phase changing that allows a 72% decrease in the 3WCC temperature estimation error during the warm up phase. This accuracy gain, occurring in a phase where the converter temperature has not reached its full efficiency, provides a 1-2% reduction in CO, HC and NO x emissions.

Numerical investigation on the thermal-flow performance of humid air-water in the interspace outside staggered tube bundles

A new model was established to investigate the thermal-flow performance of humid air-water in the interspace outside staggered tube bundles. The formation of spray water film, heat and mass transfer process between humid air and spray water including spray water droplets and film were considered in this model. The influence of structure parameters was analyzed for thermal-flow performance of humid air-water in the interspace outside staggered tube bundles. It can be found that to increase the longitudinal and transverse distance between tube bundles can improve the heat transfer performance between spray water and wall of tube bundles, and decrease the pressure drop of humid air-water. But the mass transfer between spray water and humid air will only decrease with the transverse distance between tube bundles. Meanwhile, the relative humidity of humid air is not fully utilized at the top of staggered tube bundles when the transverse distance is more than 20 mm. Otherwise, the spray water will be lost heavily at the 19–24th rows of staggered tube bundles. The row number of staggered tube bundles should be reasonably designed in term of the transverse distance. The new correlations of heat transfer and pressure drop are also obtained in term of the simulation results. The Parker's correlation will be also recommended to design the mass transfer performance of that.