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A 3D computational fluid dynamics model based on a volume of fluid (VOF) approach is presented to simulate air-water interactions and transient pressures in T-junction pipes of urban stormwater dra...

The current research focuses on the analysis of different dynamic effects of an air pocket located at mid-pipe length on transient pressures based on experimental data. Different flow rates and air...

Sufficient air concentration on aerated spillway flows can mitigate the hazard of cavitation damages on concrete surfaces of spillways. In this study, a three-dimensional two-phase flow is modelled...

A series of N-alkyl-N,N-dimethyl-N-(2,3-epoxy propyl) ammonium chloride (CnEAC, n = 10, 12, 14, 16) with alkyl of decyl, dodecyl, tetradecyl, and hexadecyl were synthesized. The adsorption properties of CnEAC under the different temperatures, concentrations, interfacial oscillation frequencies as well as the inorganic salts (NaCl and Na2CO3) at air/water interface were investigated by interfacial dilatational rheology. The dilatational properties of CnEAC solutions including complex moduli, elastic moduli and viscosity moduli increased with oscillation frequency. The elastic moduli were higher than those of viscosity ones. With different hydrogen carbon length, the complex moduli of CnEAC showed different changing role with their concentration and temperature. Inorganic salts compressed the oppositely charges on CnEAC micelle surface and induced the decrease of both complex and viscosity moduli.

In this research, the overall system performance of the solar air heater integrated with air–water heat exchanger (SAH-IAWHE) was investigated experimentally in Iraq-Samarra. V-corrugated absorber ...

Hydraulic jumps are characterized by three-dimensional motions, air entrainment and energy dissipation. While extensive air–water flow research has been conducted for classical hydraulic jumps, the...

The rewetting front propagation may occur when the fuel rod is cooled by the liquid film flow after it is dried out under accident conditions for boiling water reactor cores. Our previous study has...

Oil–air–water three-phase flow patterns in small-diameter vertical measurement channels are complex, making it difficult to establish techniques for interpretation of logging information. I...

The characterization of high-velocity air–water flows is crucial for the design of hydraulic structures including stepped spillways. Recent experimental advances have shown that LIDAR technology ca...

Air–water mixing flows are commonly formed in pressurized water supply pipes due to dissolved air from the water under low pressure conditions, and air injected through system controls and associated valves and pumps. This paper investigates transient behaviours of air–water mixing flows in viscoelastic pipes through laboratory experimental tests, numerical modelling and theoretical analysis. Two numerical schemes – the discrete vaporous cavity model (DVCM) and the discrete gas cavity model (DGCM), which are firstly calibrated and validated by the experimental data gained in this study, are adopted for comparative study for their validity and accuracy for modelling transient air–water mixing flows in viscoelastic pipes. With the validated model, the results of systematic analysis show that the effect of pipe-wall viscoelasticity on transient amplitude damping decreases with the increase of air content, and the frequency shifting rate of viscoelastic effect is negligible in comparison with that of ...

The paper describes a new eddy-currents separation technique, based on a complementary air-water method, designed for the recovery of nonferrous particles, smaller than 5 mm, from heterogeneous mix...

This study numerically investigated eight configurations of stepped spillways with 45° slopes. The rounded and sharped configurations exhibited the highest and second highest air concentrations, respectively. The baffled-shifted rounded configuration had the lowest air concentration and the highest turbulent dissipation rate and water head dissipation rate. The largest interfacial velocities and the smallest frictional drag were observed for the rounded configuration. The turbulent dissipation rate of the rounded configuration was higher than that of the sharped configuration. The silled-shifted sharped configuration had the lowest turbulent dissipation rate. Intense turbulent dissipation rates occurred in the mixing layer and the interfacial region with air concentrations of 90%. The residual energy of the baffled-shifted rounded configuration was approximately 8% and 13% lower than that of the rounded and sharped configurations, respectively. The highest residual energy under the baffled-shifted...

Countercurrent flow limitation (CCFL) may occur under certain flow conditions in the surge line, restricting the draining of water from the pressurizer and thus affecting the coolant inventory and ...

The single word that epitomises this collection is ‘rhapsodic’; rhapsodic not just in the contributors’ evident delight in their own chosen element, but in the way the essays, individually and as a...

Understanding the effects of spacer grids on the coolant flow through a nuclear reactor core is required for best-estimate design and analysis of the plant. The impact of a spacer grid on two-phase...

Recently, due to an increase in production demand in nuclear and oil and gas industries, the requirement to migrate toward larger pipe sizes for future developments has become essential. However, it is interesting to note that almost all the research on two-phase gas–liquid flow in vertical pipe upflow is based on small-diameter pipes (D ≤ 100 mm), and the experimental work on the two-phase gas–liquid flow in large-diameter (D > 100 mm) vertical pipes is scarce. Under the above circumstances, the application of modeling tools/correlations based on small-diameter pipes in predicting flow behavior (flow pattern, void fraction, and pressure gradient) poses severe challenges in terms of accuracy. The results presented in this article are motivated by the need to introduce the research work done to the industries where the data pertaining to large-diameter vertical pipes are scarce and there is a lack of understanding of two-phase gas-liquid flow behavior in large-diameter (D > 100 mm) vertical pipes.The uniqu...

Liquid-assisted laser ablation technique has become an alternative method to reduce the thermal damage of work material induced by a laser. In this study, water and ethanol were employed as the liquid to aid the laser grooving of polymethyl methacrylate (PMMA) sheet. The whole workpiece was submerged in the liquid and ablated under the different laser powers. A clean and deep groove can be fabricated when the PMMA was machined in the ethanol, while the ablation in water can introduce the smallest heat-affected zone compared to the air and ethanol environments. To realize the laser grooving performance, the ablation models were also developed for the first time in this study.

Volatile organic compounds in water and wastewater can be removed using air stripping. The effects of temperature and air-water ratios on the air stripping of benzene, toluene and xylene (BTX) from wastewater have been examined at a temperature range of 30–50°C and air-water ratios of 20–100. Removal efficiencies of >99%, >93% and 93% for BTX, respectively, were obtained at 50°C and air-water ratios of 100. The removal efficiencies increase non-linearly with temperature and air-water flow ratio. The effects of increasing temperature on the removal efficiency were found to be more significant at temperatures between 30 and 35°C than at 45 and 50°C. The effects of increasing water-air ratios on the removal efficiency were more significant at air-water ratios of 20–60 than at 80–100. The results indicate that a high removal of BTX can be achieved by operating the air stripper at high temperature conditions even at relatively low air-water ratios and vice versa.

A monolayer of a ferroelectric liquid crystal (FLC) at an air–water interface has been deposited onto solid substrates using the Langmuir–Blodgett technique. On compression, molecules on the water ...

This experimental study examines the two phase flow structures of airflow pressures for annular flow through a 900 bend, with and without, a vortex fin for drainage applications. The superficial li...

This article presents the results of experiential investigations of frictional pressure drop in horizontal minichannels. An air–water mixture was used as the working fluid. The test section was made from stainless-steel pipes with internal diameters of 1.05, 1.35, 1.68, and 2.30 mm. Investigations were carried out at mass flux of 170–7350 kg/m2-s and gas quality from 0.001 to 0.22. Superficial velocity ranges of water and air were 0.2–7.4 m/s and 1.7–41.8 m/s, respectively. The results of experimental investigations were compared with theoretical values obtained from a homogeneous equilibrium model. The dynamic viscosity coefficient was calculated using dependences proposed by Owens, McAdams, Ackers, Cicchitti, Dukler, Beattie and Whalley, and Lin. It is found that none of the tested correlations can predict the two-phase pressure drop gradient satisfactorily. The homogeneous model with a correction factor proposed by Chen to use in minichannels was also used. In this case, the results of calculations wer...

For centuries, hydraulic engineers were at the forefront of science. The last forty years marked a change of perception in our society with a focus on environmental sustainability and management, particularly in developed countries. Herein, the writer illustrates his strong belief that the future of hydraulic engineering lies upon a combination of innovative engineering, research excellence and higher education of

Socioeconomics introduced risk acceptance criteria in order to assess the affordability of health related measures some decades ago. Later, engineering risk criteria were derived partly on this basis with the aim of determining an admissible and affordable safety level for facilities involving loss of human life in case of failure. The present paper shows how to apply the latter type of criterion to toxic long-term effects, while including aspects such as demography and discounting.

Isolation and Characterization of Naphthenic Acids from Metal Naphthenate Deposit : Molecular Properties at Oil-Water and Air-Water Interfaces

Calibrating and testing forensic breath test instruments using wet-bath simulators heated to 34°C is fundamentally dependent on the assumed air/water partition coefficient for ethanol employed. Models developed from the early experimental work of Harger et al. (1950), defining the partition coefficient as a function of temperature, have formed the basis for many calibration and testing protocols. However, it appears these models may have been developed from the inappropriate fitting of log-transformed data by linear least squares. Fitting the data appropriately by nonlinear regression yields a model that, if employed, would calibrate an instrument lower by 2.5% relative to the naive model. Moreover, the more appropriate model is in better agreement with the more recently published models of Dubowski (1979) and Jones (1983). Forensically, the effect on instrument calibration is insignificant with a maximum difference of only 2.5%.

Although evasion of elemental mercury from aquatic systems can significantly deplete net mercury accumulation resulting from atmospheric deposition, the current ability to model elemental mercury air/water exchange is limited by uncertainties in our understanding of all gaseous air/water exchange phenomena in addition to limitations unique to this element. A critical review of the technical literature is performed; a new estimate for the diffusivity of elemental mercury in water is obtained; a Setschenow coefficient for elemental mercury is published; and a normalized version of the Cole and Caraco (1998) low to intermediate windspeed air/water gaseous exchange model is developed. Findings from the study include: (1) some previously published estimates of elemental mercury diffusivity in water are likely too high by as much as a factor of four; (2) some published Schmidt number estimates are likely too low (by a similar factor); (3) some previously published elemental mercury air/water exchange es...

This fully revised and updated version of the Handbook covers all aspects of environmental analysis and examines a large number of substances and compounds of environmental concern. The book includ...

Heretofore unknown flow regimes of air-water counterflow through a pair of transparent, vertical, parallel cross corrugated plates were observed via high-speed video. Air flows upward driven by pressure gradient and water, downward driven by gravity. The crimp geometry of the corrugations was drawn after typical corrugated sheets used as filling material in modern structured packed towers. Four regimes were featured, namely, rivulet, bicontinuous, flooding-fronts, and flooding-waves. It is conceivable that the regimes observed might constitute the basis for understanding how gas and liquid phases contend for available space in the interstices of structured packings in packed towers. Flow regime transitions were expressed in terms of liquid load (liquid superficial velocity) and gas flow parameter of common use in pressure drop and capacity curves. We have carefully examined the range of parameters equivalent to the ill-understood high-liquid-flow operation in packed towers. More importantly, our findings ...

The effects of vessel size and vessel aspect ratio on the formation of the air-water hollow profile under microgravity were experimentally evaluated. We investigated these parameters at various rotating speeds of vessels and variable water/vessel volume ratios using the drop towers at the Japan Microgravity Center and the National Institute of Advanced Industrial Science and Technology Hokkaido Center. The discriminate of the formation of the air-water hollow profile could be determined by the aspect ratio of the vessel, the modified Weber number and the volume ratio of water/vessel.

New experimental data are obtained for pressure drop and entrainment for annular upflow in a vertical pipe. The 9.5-mm pipe has a hydraulic diameter similar to the subchannels in the fuel assemblies of water-cooled reactors. The test section has a length-to-diameter ratio of 440 to ensure fully developed annular flow. The pressure covers the range from 140 to 660 kPa. Therefore, the density ratio is varied by a factor of -4. This allows the investigation of the effect of pressure on the interfacial shear models. Gas superficial velocities between 25 and 126 m/s are tested, extending the range of previous data to higher gas velocities. The data are compared with well-known models for interfacial shear that represent the state of the art. Good results are obtained with the models by Wallis, and Henstock and Hanratty. When the model by Asali, Hanratty, and Andreussi is modified for the effect of pressure, the agreement is also good, and the data collapse with very little scatter. There is a close relationship between these models and mixing length theory such that the models may be viewed as correlations for the surface roughness. This points toward a more fundamental approach in terms of the interfacial structure.

A mathematical model was developed to predict the air concentration profiles in the deaeration zone below a spillway aerator by solving the conservation equations of mass and momentum. The turbulent diffusion coefficient was calculated by a k-∊ model and the air-water mixture was treated as a stratified flow. To test the mathematical model a series of experiments was conducted. Air was injected from the bed of a flow channel and air concentration profiles were measured at various downstream sections. From the comparison of the computer predictions with the experimental data it was concluded that the present analytical approach was satisfactory for practical purposes and showed promise for further development.

Proteins are very surface‐active substances, which means that they readily adsorb onto O/W and A/W interfaces, even if present in very low concentration. They do not yield a very low interfacial tension. Adsorption, conformation in the interface, and the various interfacial properties resulting from their adsorption are briefly reviewed, especially in relation to formation and stability of emulsions and foams. Displacement from the interface by small‐molecule surfactants is also discussed. It is concluded that most effects of adsorbed proteins on the various kinds of physical instability of emulsions and foams are semiquantitatively understood, but that the variation among proteins in the production of small droplets and bubbles during emulsification and foaming, respectively, still largely defies explanation. It makes little sense to classify proteins according to their suitability for emulsification or foaming, because each of the physical properties of these systems may depend in a different w...

SummaryDuring drought, stomata allow the regulation of CO2 and water vapor exchanges of the plant. The relationships between stomatal conductance and leaf water potential and the stomatal responses to air water vapor deficit are studied and their mechanisms analysed. The partial control of photosynthesis by stomata is reexamined taking into account the new results showing a stomatal aperture patchiness on the leaf during drought. In a last part, interest and limitations of the use of stomatal responses in plant breeding for more drought resistant cultivars are discussed in relation to the overall mechanisms of drought resistance in the plant kingdom.

Air-water flows in urban drainage systems are among the most interesting and complex research topics. The phenomena are present everywhere in roof drainage systems, gully pots, sewers, pressurised ...

The interaction of the amphoteric surfactant Empi-gen BB (Em) with lecithin at the air/water and xylene/ water interfaces was studied at the isoelectric point of lecithin (pH≃3). Surface and interfacial tension, surface elasticity and viscosity measurements and elec-trophoretie mobility data showed that the interaction between lecithin and Em leads to the formation of a mixed film with no elasticity and very low interfacial viscosity. The coalescence rate K of xylene/water emulBion was measured by droplet counting as a function of time. The results showed that the emulsions stabilised with the mixed surfactant and lecithin films were less stable than those stabilised with lecithin alone. This showed the importance of the Theological property of the film in reducing coalescence.

An investigation is reported in which nylon 6.6 fibres were fatigued while they were immersed in different liquid environments and the effect of the environment was studied. Hydrochloric acid was found to reduce the fatigue lives of nylon fibres considerably. A comparison of the effects of corrosive environments on tensile and fatigue properties shows that the effect on fatigue is much the more significant.

Friction and wear of hot-pressed Si3N4 sliding on itself at low velocity (1 mm/s) were measured at room temperature in humid air, water, pure hexadecane and in hexadecane with 0.5 percent stearic acid. The friction coefficients in air and water are 0.75 and 0.65, respectively. In hexadecane with stearic acid, the friction coefficient is 0.1, somewhat higher than for metals. In pure hexadecane, the friction coefficient is 0.12, much lower than for metals, suggesting strong adsorption of the hydrocarbon. The wear rate is approximately constant k = 5 × 10−11 kg/Nm in humid air and water. It is much lower in hydrocarbon lubricants and varies with (sliding distance)2/3 in dexadecane and with (sliding distance)1/3 with stearic acid. A tribochemical reaction occurs between silicon nitride and water in all four environments; in the hydrocarbons the reaction is with water dissolved in the fluids. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Tribology Conference in Pittsburgh, Pe...

Two series of 60Co irradiations have been performed on air/water mixtures, one with both gas and liquid phases present and the other with only air-saturated liquid phase. A third series of irradiations was conducted with two-phase nitrogen/water mixtures. The data confirm that direct interaction of radiation with the gas, presumably the N2 molecule, is required to generate nitric acid. An additional requirement for the production of nitric acid is the presence of both N2 and O2 in the gas phase. Data from previous studies show that the reaction mechanism is modified somewhat when neutron or alpha irradiation is involved.

By presenting the saturation humidity as a quadratic function of temperature, an analytical equation was obtained which is capable of calculating the change of water temperature in an adiabatic air-water contact tower. Also, analytical equations were obtained to predict changes of water and air temperatures and the air-water interface temperature in the lower by approximating the saturation humidity as a linear function of temperature. Solution to practical problem is given to demonstrate the use of the analytical equations in the design of an adiabatic air-water contact tower.

(1969). Earth, Air, Water. Environment: Science and Policy for Sustainable Development: Vol. 11, No. 6, pp. 14-33.

Concentrations of 210Pb and 210Po in air, drinking water, foodstuffs, and human tissues are reported. The main route of 210Pb and 210Po intake in the human body is ingestion with foodstuffs. The absorption coefficient of 210Po into the blood from the digestive tract was estimated to be 35%. The highest concentration of 210Pb and 210Po in the body was observed in the skeleton and hair. The body burden of humans was 773 pCi of 210Pb and 513 pCi of 210Po. Excretion of these radionuclides from the body in urine was 14 to 15 times less than in feces. The calculated annual radiation doses of 710Po in the bone, liver, and kidneys were 2.1 to 5.0 millirad/yr, and in other soft tissues, 0.3 to 0.9 millirad/yr.

(1986). Air-Water Two-Phase Cross Flow Resistance in Rod Bundle. Journal of Nuclear Science and Technology: Vol. 23, No. 7, pp. 658-660.