Capillary Flow Of Water Research Articles

Analysis of Capillary Water Absorption within Unsaturated Concrete Based on the Principle of Stationary Action

Capillary water absorption plays a critical role in the ingress of corrosive elements during the construction of concrete structures in corrosive environments. This study presented a novel approach for analyzing capillary water flow within unsaturated concrete based on the principle of stationary action. The flow of water within the concrete capillary pores can be regarded as a variational problem, while the principle of stationary action provides a method for determining the path solution. The evolution and distribution characteristics of water content and wetting front were explicitly determined using the exponential and power hydraulic functions. A simplistic yet effective approach for determining these hydraulic parameters was put forward based on the relationship between the position of the wetting front and the diffusivity parameters. The proposed approach exhibited enhanced theoretical robustness and entailed fewer hypotheses compared to existing methodologies. Furthermore, the material hydraulic parameters in the proposed approach can be determined explicitly. The governing equations for capillary water flow were derived in accordance with the principle of stationary action. Numerical simulations were carried out to verify the effectiveness of the proposed approach. The results demonstrated that the proposed approach can accurately predict capillary water flow and diffusivity parameters within unsaturated concrete. The findings of this study contribute to developing more effective strategies to mitigate moisture-related damage in concrete structures.

Surface wettability and capillary flow of water in nanoslits of two-dimensional hexagonal-boron nitride

Surface wettability and capillary flow of water in nanoslits of two-dimensional hexagonal-boron nitride

Abnormal wicking dynamics of total wetting ethanol in graphene nanochannels

Although the unexpectedly fast capillary flow of water (partial wetting) in graphene nanoslits has been reported, the wicking dynamics of total wetting liquid in a nanocapillary have not been studied. In this work, the spreading behavior on graphene sheets and the imbibition process in graphene nanochannels are explored by molecular dynamics for ethanol (total wetting). For spreading dynamics, two regimes are identified: inertia-dominated initial spreading and viscous spreading with an exponent greater than Tanner's law. For imbibition dynamics, the total wetting liquid behaves quite differently from the partial wetting liquid. The advancing motions of both the precursor film and main flow are clearly seen, and their advancing lengths are proportional to the square root of time. However, the proportional constant of the former, which is independent of channel widths, is greater than that of the latter, which decreases with increasing channel widths. Both the thickness of the precursor film and the diameter of curvature of the menisci, which is less than the channel width, grow with increasing channel widths. For very narrow nanoslits, the precursor film cannot be distinguished from the main flow, and the surprisingly rapid imbibition behavior is observed.

Capillary flow of water in tubes partially prefilled with oil

When water meets sunflower oil in a horizontal capillary tube, a water droplet can spontaneously form. The position of the breakup event can be manipulated by simply adjusting the oil content that prefills the capillary. For short length scales, the system advances with a constant velocity making it a good predictive tool for engineering applications.

Estimation of the hydraulic conductivity of unsaturated soil incorporating the film flow

In the conventional method for the estimation of the hydraulic conductivity of unsaturated soil, only the capillary water is considered in the estimation. However, it is known that a water film can be formed around soil particles due to the adsorptive force. The water may migrate in the soil through the water film. As a result, both water flow in the capillary water and water film should be considered in the estimation. In this paper, a new equation was proposed for the estimation of the hydraulic conductivity of unsaturated soil by considering the film flow. The proposed method was verified with the experimental data from the literature. It is recommended that both capillary water flow and film flow should be considered in the estimation of the hydraulic conductivity of unsaturated soil.

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Direct electricity generation from water flow/evaporation, coined hydrovoltaic effect, has recently attracted intense interest as a facile approach to harvest green energy from ubiquitous capillary water flow or evaporation. However, the current hydrovoltaic device is inferior in output power efficiency compared to other renewable energy devices. Slow water evaporation rate and inefficient charge collection at device electrodes are two fundamental drawbacks limiting energy output efficiency. Here, we report a bioinspired hierarchical porous fabric electrode that enables high water evaporation rate, efficient charge collection, and rapid charge transport in nanostructured silicon-based hydrovoltaic devices. Such an electrode can efficiently collect charges generated in nanostructured silicon as well as induce a prompt water evaporation rate. At room temperature, the device can generate an open-circuit voltage (Voc) of 550 mV and a short-current density (Jsc) of 22 μA·cm-2. It can output a power density over 10 μW·cm-2, which is 3 orders of magnitude larger than all those reported for analogous hydrovoltaic devices. Our results could supply an effective strategy for the development of high-performance hydrovoltaic devices through optimizing electrode structures.

Computational Simulation of Spontaneous Liquid Penetration and Depression Between Vertical Parallel Plates

Abstract A computational fluid dynamics model is developed to study the dynamics of meniscus formation and capillary flow between vertical parallel plates. An arbitrary Lagrangian–Eulerian approach is employed to predict and reconstruct the shape of the meniscus with no need to employ implicit interface tracking schemes. The developed model is validated by comparing the equilibrium capillary height and meniscus shape with those predicted by available theoretical models. The model was used to predict the capillary flow of water in hydrophilic (silver) and hydrophobic (Teflon) vertical channels with wall spacings ranging from 0.5 mm to 3 mm. It is shown that the computational model accurately predicts the capillary flow regardless of the channel width, whereas the theoretical models fail at relatively large wall spacings. The model captures several important hydrodynamic phenomena that cannot be accounted for in the theoretical models including the presence of developing flow in the entrance region, time-dependent formation of the meniscus, and the inertial effects of the liquid in the reservoir. The sharp interface tracking technique enables direct access to the flow variables and transport fluxes at the meniscus with no need to use averaging techniques.

Temperature Effect on Capillary Flow Dynamics in 1D Array of Open Nanotextured Microchannels Produced by Femtosecond Laser on Silicon.

Capillary flow of water in an array of open nanotextured microgrooves fabricated by femtosecond laser processing of silicon is studied as a function of temperature using high-speed video recording. In a temperature range of 23–80 °C, the produced wicking material provides extremely fast liquid flow with a maximum velocity of 37 cm/s in the initial spreading stage prior to visco-inertial regime. The capillary performance of the material enhances with increasing temperature in the inertial, visco-inertial, and partially in Washburn flow regimes. The classic universal Washburn’s regime is observed at all studied temperatures, giving the evidence of its universality at high temperatures as well. The obtained results are of great significance for creating capillary materials for applications in cooling of electronics, energy harvesting, enhancing the critical heat flux of industrial boilers, and Maisotsenko cycle technologies.

Transpiration Driven Electrokinetic Power Generator.

Transpiration is the process by which water is carried in plants from the roots to the leaves where evaporation takes place. Here, we report a transpiration driven electrokinetic power generator (TEPG) that exploits capillary flow of water in an asymmetrically wetted cotton fabric coated with carbon black. Accumulation of protons induced by the electrical double layer formed at the solid (carbon black)/liquid (water) interface gives rise to potential difference between the wet and dry sides. The conductive carbon black coating channels electrical current driven by the pseudostreaming mechanism. A TEPG of 90 mm × 30 mm × 0.12 mm yields a maximum voltage of 0.53 V, maximum current of 3.91 μA, and maximum energy density of 1.14 mWh cm-3, depending on the loading of the carbon black. Multiple TEPGs generate enough power to light up a light-emitting diode (20 mA × 2.2 V) or charge a 1 F supercapacitor.

Unsaturated permeability of Gaomiaozi bentonite under partially free-swelling conditions

In the deep geological disposal of high-level radioactive wastes (HLW), Na-bentonite produced from Gaomiaozi (GMZ) deposit has been selected as a possible buffer and backfill material for the Beishan repository in China. A sealing buffer is manufactured with bentonite at its hygroscopic water content (initially unsaturated). After taking water from the surrounding geological medium, bentonite under totally free condition is used to seal the technological voids, and then the outer surrounding bentonite (affected by the water mostly) compresses the innermost bentonite under partially free-swelling condition. However, permeability of GMZ bentonite under the partially free-swelling condition is still unknown. In this article, using the instantaneous profile method, we present a laboratory test of the GMZ bentonite unsaturated hydraulic conductivity under partially free-swelling condition. Changes in the cross-sectional area and motion of the sensors (to measure temperature and relative humidity) were considered in computing the unsaturated permeability. Our experimental results show that before the finial hydration stage, although permeability increases locally at some suctions (due to saturation degree increase and bentonite swelling to some extent), unsaturated permeabilities decrease and become constant in general for the reasons as follows. Initially, water is tightly adsorbed to the clay sheet surface and then water film is adsorbed to the tightly adsorbed water which leads to the initial highest permeability, and then diffuse double-layer forces lead to water uptake between the hydrated montmorillonite unit layers which is partially restricted by the confining stress, while capillary water flows on the water adsorbed on the internal surface of the bentonite large pores. For the capillary water flow due to surface tension, complex microstructure evolution (e.g., mesoscopic swelling compacts the inter-aggregate pores due to hydration under the confining stress from the rubber tube) before the finial hydration stage leads to flux decrease if under a certain hydraulic gradient (i.e., permeability decreases). Results show that in the final hydration stage, permeability increases rapidly with decreasing suction, because large pore compacting is complete while saturation degree increases and bentonite swells to some extent. Results show that at the same suctions, the unsaturated permeabilities located at the sensor closest to the water injection device are the largest among the four sensors, which could be explained with “critical gradient” concept for unsaturated expansive clay or effect of hydraulic gradient from boundary water pressure.

EFFECTS OF SURFACE PROPERTIES ON FLUID ENGINEERING GENERATED BY THE SURFACE-DRIVEN CAPILLARY FLOW OF WATER IN MICROFLUIDIC LAB-ON-A-CHIP SYSTEMS FOR BIOENGINEERING APPLICATIONS

In this research paper, in total 212 individual leakage-free Polymethylmethacrylate (PMMA) microfluidic devices are fabricated by maskless lithography, hot embossing lithography and direct bonding technique. The effect of channel aspect ratio on dyed water flow is investigated using these microfluidic devices. Experimental studies show that the dyed water flow is faster on the surface of higher wettability. The effect of capillary pressure on dyed water flow is studied in the fabricated PMMA microfluidic devices. According to the experimental observations, the centrifugal force has prominent effect on the dyed water flow. Also, the effect of bend angle is investigated on the surface-driven capillary flow of water. The polystyrene microparticles have been separated in the microfluidic lab-on-a-chip systems using the investigated flow features. A 100% separation efficiency is achieved in these lab-on-a-chip systems. These microfluidic lab-on-a-chip systems can be used to separate blood cells from human whole blood for further clinical tests. These experimental studies are important in bioengineering applications. The effect of bend angle as channel geometry to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems. Also, the effect of surface wettability as surface property to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems.

Fizikalne in mehanske lastnosti svežega in osušenega lesa v bukovih deblih, izruvanih med žledolomom

Physical and mechanical properties of beech wood (Fagus sylvatica L.) from trees fallen in ice storm were determined. The properties were studied in parallel green and dried beech-wood samples, systematically collected along the radius and at different height levels of the stem. The stiffness of the timber was comparatively tested with static 4-point bending and non-destructively by measuring the speed of ultrasound, and by determining the frequency response. The bending and shear strengths were additionally determined along the grain, as well as compression strength in all anatomical directions of wood. In blown down trees with still partly preserved root system, active crown and sufficient capillary water flow, we could not detect any reduction of mechanical properties due to deterioration. The density and mechanical properties, except transverse compression strength, increased with increasing height in the tree and radially from the pith to the cambium. They were always better in dried than in green wood. The reliability of non-destructive methods was greater in the evaluation of dried wood. We recommend visual wood characterisation in addition to the use of non-destructive methods for strength assessment of wood.

Role of morphological structure and layering ofSphagnumandTomenthypnummosses on moss productivity and evaporation rates

Goetz, J. D. and Price, J. S. 2015. Role of morphological structure and layering of Sphagnum and Tomenthypnum mosses on moss productivity and evaporation rates. Can. J. Soil Sci. 95: 109–124. Morphological structures of peatland mosses control moss water relations and the rate of water loss by drainage and evaporation, thus influencing their physiological functions. While many of these mechanisms are understood for Sphagnum mosses, there is a limited understanding of how these processes operate in Tomenthypnum nitens, a dominant brown moss species in northern rich fens. This study contrasts how different hydrophysical characteristics of Tomenthypnum and Sphagnum species affect capillary water flow that supports evaporation and productivity. Laboratory investigations indicate that volumetric water content (θ), gross ecosystem productivity, and evaporation decreased with water table depth for both mosses, with Sphagnum capitula retaining 10–20% more water (θ range of 0.18–0.32 cm3cm−3) than Tomenthypnum (0.07−0.16 cm3cm−3). Despite lower θ and a smaller fraction of pores between 66 and 661 µm to retain water within the Tomenthypnum structure (10%) compared with Sphagnum (27%), both mosses had similar fractions of water conducting pore spaces and were able to maintain capillary rise throughout the experiment. While there was a larger difference in the bulk density and porosity of the Tomenthypnum moss compared with its underlying peat than there was in the Sphagnum profile, a layer of partially decomposed moss of intermediate properties was sufficient to provide a connection between the moss and peat under low water table conditions. In trying to characterize the soil-water pressure (ψ) in near-surface mosses of Tomenthypnum based on measurements of vapour pressure, we found disequilibrium conditions that severely underestimated ψ (i.e., very large negative pressures). It is this disequilibrium that drives evaporation and draws up capillary water to the moss surface for peatland–atmosphere carbon and water transfers.

A new thermocouple technique for the precise measurement of in-plane capillary water flow within fabrics

A new method was proposed for the measurement of in-plane capillary water flow within fabrics automatically. The method was based on the use of thermocouples to measure temperature changes as the fabric absorbed water. The wicking length of three different woven fabrics and two knitted fabrics in the warp, weft and 45° bias directions was measured using this technique. The wicking length was found to have a linear relationship with the square root of time, in agreement with the Washburn equation. Comparing the results with the data acquired using the horizontal Byreck method, the thermocouple technique was found to be suitable for the precise measurement of in-plane capillary water flow through fabrics automatically. Moreover, based on this method, the feasibility of estimating the water contents of fabrics from temperature differences generated during the flow process was also investigated. We found that it was possible to estimate the water content of a fabric, provided the moisture level is below the critical water content at equilibrium. This can be used to estimate the water content of fabric when it is worn.

Unsaturated hydraulic properties of xerophilous mosses: towards implementation of moss covered soils in hydrological models

Evaporation from mosses and lichens can form a major component of the water balance, especially in ecosystems where mosses and lichens often grow abundantly, such as tundra, deserts and bogs. To facilitate moss representation in hydrological models, we parameterized the unsaturated hydraulic properties of mosses and lichens such that the capillary water flow through moss and lichen material during evaporation could be assessed. We derived the Mualem-van Genuchten parameters of the drying retention and the hydraulic conductivity functions of four xerophilous moss species and one lichen species. The shape parameters of the retention functions (2.17?

TCH-006 Development and Validation of 3 Methods – UV Spectrophotometry, Flow Injection Analysis and Liquid Chromatography – For the Control of Nystatin Capsules.

BackgroundAs an alternative to amphotericin B used for selective digestive decontamination, physicians asked the Hospital Pharmacy for the preparation of nystatin capsules, 500,000 IU.PurposeThree methods were considered for routine checking:...

Effects of compaction during drilling on yield of sugar beet (Beta vulgaris L.)

Excessive soil compaction can reduce crop growth, but compaction can also have positive effects, e.g. increasing soil unsaturated hydraulic conductivity and thereby the capillary flow of water and nutrients to seeds and plants. There may thus be an optimum state of compactness for plant growth.This study examined the effect of different levels of compaction on sugar beet growth and sugar yield in a total of 10 field experiments performed during 2006–2008, mainly on sandy loams (Eutric Cambisols). In most cases, the soil had been mouldboard-ploughed in autumn. A newly constructed sugar beet seed drill with press wheels was used to create different levels of compaction directly around the seed. Greater compaction was achieved by 1 or 3 passes by tractor wheels over the soil. The actual degree of soil compaction was determined by measuring bulk density at 5–10cm depth and penetration resistance to 30 or 35cm depth. Crop growth was determined by measuring root and plant biomass in mid-June and final sugar beet yield. The concentration of plant nutrients in sugar beet foliage was also determined. Two additional experiments in 2009 examined different levels of traffic in combination with mouldboard ploughing or chisel ploughing to 10 or 20cm depth.On average, one pass with a tractor wheel increased yield compared with uncompacted soil, but increasing the compaction by press wheels on the seed drill had little effect on yield. In most cases, even three passes with tractor wheels had no harmful effect on sugar yield. The effect of traffic on nutrient concentrations in the plant was also very small. In one experiment, shallow tillage with a chisel plough lowered yield compared with mouldboard ploughing. There was also an interaction between the effects of primary tillage and compaction in the spring, with more negative effects after shallow tillage.Overall, the sugar beet crop was relatively insensitive to different levels of traffic applied at the time of sowing. The results indicate that the risk of yield losses due to compaction caused by normal traffic after autumn ploughing is low. However with ploughless tillage, soil bulk density may be too high for optimal growth regardless of traffic during seedbed preparation.

Nanoscale surface modifications to control capillary flow characteristics in PMMA microfluidic devices

Polymethylmethacrylate (PMMA) microfluidic devices have been fabricated using a hot embossing technique to incorporate micro-pillar features on the bottom wall of the device which when combined with either a plasma treatment or the coating of a diamond-like carbon (DLC) film presents a range of surface modification profiles. Experimental results presented in detail the surface modifications in the form of distinct changes in the static water contact angle across a range from 44.3 to 81.2 when compared to pristine PMMA surfaces. Additionally, capillary flow of water (dyed to aid visualization) through the microfluidic devices was recorded and analyzed to provide comparison data between filling time of a microfluidic chamber and surface modification characteristics, including the effects of surface energy and surface roughness on the microfluidic flow. We have experimentally demonstrated that fluid flow and thus filling time for the microfluidic device was significantly faster for the device with surface modifications that resulted in a lower static contact angle, and also that the incorporation of micro-pillars into a fluidic device increases the filling time when compared to comparative devices.

On the regularity of capillary water waves with vorticity

We study the regularity of the streamlines and of the free-surface in a capillary water flow with underlying currents.

Modeling the Rehydration Process of Dried Tomato

Rehydration of air-dried tomatoes was investigated at four temperatures (25, 40, 60, and 80°C). To describe the rehydration kinetics, two empirical models, Peleg and Weibull, were considered. The empirical models described the rehydration process properly. The equilibrium moisture content decreased as rehydration temperature increased, whereas the kinetic constants of the Peleg and Weibull models, k 1 and β, respectively, increased with increasing temperature. This influence was described in terms of an Arrhenius relationship. The Peleg constant k 2 was also found to be a function of temperature, increasing as temperature increased, whereas the Weibull shape parameter α decreased with increasing temperature. In addition, a mathematical model based on one-dimensional, steady-state, fully developed capillary flow of water with negligible inertia effects within the air-dried tomato was developed. This model was found to adequately describe the rehydration behavior of dried tomatoes.