Water Drop Diameter Research Articles

Experimental Study of Frost Crystals Dendrite Growth on Two Neighboring Separate Frozen Water Drops on a Cryogenic Cold Surface under Natural Convection Conditions

The effects of cold surface temperature, wet air state (temperature and humidity) and original drop size on frost dendrites growth of two neighboring separate frozen water drops of same size under natural convection conditions were investigated by quantitative measurement. It was determined that for different cold plate surface temperature conditions, i.e., the ordinary-low temperature and the cryogenic temperature range, the frost formation mechanism is different. Under the conditions that the air temperature is not too high and absolute humidity is not too excessive, the influence of frozen water drop size on the longest dendrite of frost crystals becomes more and more obvious with the decrease in cold plate temperature. The changes in air temperature and relative humidity both change air absolute humidity, so they have similar effects on the growth of dendrites. However, the effect of wet air state on the growth of frost dendrites is not monotonous, which needs to be considered comprehensively in combination with heat and mass transfer and the existence of heavy phase layer. The thickness of ‘the initial continuous frost layer’ was measured and it was disclosed that the initial frost layer thickness is 1.7–3.0 times that of the height of the frozen water drop diameter. This value may be possibly used as initial frost layer thickness in heat and mass transfer-based frost layer growth prediction models, at least for ordinary-low temperature conditions.

Differentiating Freezing Drizzle and Freezing Rain in HRRR Model Forecasts

AbstractSupercooled large drop (SLD) icing poses a unique hazard for aircraft and has resulted in new regulations regarding aircraft certification to fly in regions of known or forecast SLD icing conditions. The new regulations define two SLD icing categories based upon the maximum supercooled liquid water drop diameter (Dmax): freezing drizzle (100–500 μm) and freezing rain (>500 μm). Recent upgrades to U.S. operational numerical weather prediction models lay a foundation to provide more relevant aircraft icing guidance including the potential to predict explicit drop size. The primary focus of this paper is to evaluate a proposed method for estimating the maximum drop size from model forecast data to differentiate freezing drizzle from freezing rain conditions. Using in situ cloud microphysical measurements collected in icing conditions during two field campaigns between January and March 2017, this study shows that the High-Resolution Rapid Refresh model is capable of distinguishing SLD icing categories of freezing drizzle and freezing rain using a Dmax extracted from the rain category of the microphysics output. It is shown that the extracted Dmax from the model correctly predicted the observed SLD icing category as much as 99% of the time when the HRRR accurately forecast SLD conditions; however, performance varied by the method to define Dmax and by the field campaign dataset used for verification.

Formation of Gold Nanoparticles in Water-in-Oil Microemulsions: Experiment, Mechanism, and Simulation

Self-assembled water-in-oil (W/O) microemulsions have been reported as a suitable route for synthesis of size-controlled nanoparticles. However, the mechanism of formation of nanoparticles in microemulsions is still not completely understood. In this work, gold nanoparticles (GNPs) were synthesized via the W/O microemulsion route. As the molar ratio of water and dioctyl sodium sulphosuccinate (AOT) (R) increased from 2.5 to 5.0 to 7.5, the corresponding water drop diameter increased from 2.7 to 5.0 to 7.3 nm. In parallel, the mean hydrodynamic diameter of GNPs increased from 6.5 to 11.3 to 15.6 nm for corresponding R values of 2.5, 5.0, and 7.5. Therefore, although there is a monotonically increasing trend of the mean diameter of GNPs with the initial drop diameter, for all values of R, the mean diameter of GNPs was significantly higher than the initial drop diameter. Consequently, previously known simulation vastly underpredicts the experimental GNP diameter. However, only on redefining the particle-particle coagulation event (during coalescence of microemulsion drops containing particles) does the current kinetic Monte Carlo (kMC) simulation agree well with the experimental results. In addition, we also find that the coagulation efficiency of solid nanoparticles (βp) increases with R, and βp is lesser than the coalescence efficiency of liquid drops (βd) over the range of R values concerned. Hence, a combined simulation and experimental study enumerates the dynamics of size evolution of nanoparticles and the events involved in their formation in a W/O microemulsion system.

Infiltration of impacting droplets into porous substrates

The impact of water droplets on thin porous layers of glass beads held vertically between glass plates was photographed to observe simultaneous spreading and infiltrating of the liquid into the porous medium. Glass beads with diameters of either 100 µm or 500 µm were tested and micro-computed tomography was used to measure the porosities of the layers. The water drop diameter was kept constant at 2 mm while the impact velocity was varied from 0.06, to 1.9 m/s. High-speed videos of the advance of water into the porous structure were studied with image analysis software and the volume flow rate of liquid calculated. Increasing droplet impact velocity decreases droplet infiltration time because higher droplet inertia drives more liquid into the porous material and a larger droplet spreading diameter increases the area in contact with the substrate. Too high of an impact velocity results in droplet cleaving where a portion of the drop remains on the upper surface. A simple model is proposed to determine when inertia driven infiltration will be significant. Once droplet inertia is dissipated capillary forces draw liquid into the substrate and analytical models are compared to predict the rate of capillary driven flow.

マイクロバブルを利用した液滴の微粒化（気泡径とボイド率が液滴径に及ぼす影響）

The atomization technology of liquid is applied to a lot of fields like internal combustion engine, agriculture, chemistry, food, and medical supply, etc. now, and the important technology for solving the problems of environmental problems and energy conservation. In recent years, a micro bubble with diameter of tens of μm or less is paid to attention. As for this micro bubble, various characteristics that bubble with diameter of several mm doesn't have are possessed and, for instance, water purification, oil separating, growth promotion of creature, and reduction of frictional resistance are reported. In this study, it was examined whether making a further water drop minute was possible by mixing micro bubbles into water using a whirl type injection valve. Moreover, the influences of micro bubble diameter and void fraction on water drop diameter were examined. As a result, in low-pressure of atomizing pressure Ps=0.2MPaG, the maximum 32% effect of atomization was able to be achieved by mixing micro bubbles into water. Moreover, it was clarified that the effects of atomization were almost the same in 0.1% or more of void fraction.

Experimental study of a drop “evolution” under conditions of its free fall on a heated surface

Time dependences of distilled water drop diameter were obtained experimentally after its falling on a heated copper substrate from a height of 0.09 m. The temperature of the solid surface ( Tw ) varied from 333 to 413 K in steps of 20 K. The effect on the drop dynamics after falling and the maximum ratio of the spreading diameter to the drop diameter in flight ( βmax ) were determined.

Experimental study on latent heat storage characteristics of W/O emulsion -Supercooling rate of dispersed water drops by direct contact heat exchange-

Recently, much attention has been paid to investigate the latent heat storage system. Using of ice heat storage system brings an equalization of electric power demand, because it will solved the electric -power-demand-concentration on day-time of summer by the air conditioning. The flowable latent heat storage material, Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enable to transport the latent heat in a pipe. The flowable latent heat storage material can realize the pipe size reduction and system efficiency improvement. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase brings the obstruction of latent heat storage. The latent heat storage rates of dispersed water drops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The water drops in emulsion has the diameter within 3 ~ 25μm, the averaged water drop diameter is 7.3μm and the standard deviation is 2.9μm. The direct contact heat exchange method is chosen as the phase change rate evaluation of water drops in W/O emulsion. The supercooled temperature and the cooling rate are set as parameters of this study. The evaluation is performed by comparison between the results of this study and the past research. The obtained experimental result is shown that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It was clarified that the supercooling rate of dispersed water particles in emulsion shows the larger value than that of the bulk water.

분수에서 생성되는 물입자의 확산과 냉각효과의 범위 예측

This research was done to clarify the cooling effect of water particles generated from a fountain. This effect is a one way to control the heat island effect of big cities. The result of this research was drawn by setting the jets of water in a certain height, and then studying the diffusion of water particles, which is affected by the size of the particles and the wind speed, and the cooling effect caused by the diffusion. 1) When a diameter of a water drop was 500 <TEX>${\mu}m$</TEX> and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 75 to 190m, and the water vapor spread over 175 to 440 m. As a result, there was more than <TEX>$0.5^{\circ}C$</TEX> of cooling effect on the temperature in the atmosphere 130 to 330m around the water fountain. 2) When a diameter of a water drop was 750 <TEX>${\mu}m$</TEX> and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 65 to 150 m, and the water vapor spread over 160 to 405 m. Moreover, there was more than <TEX>$0.5^{\circ}C$</TEX> of cooling effect on the temperature in the atmosphere 110 to 275 m around the water fountain. 3) After studying on the relationship between the diameter of water drop and the wind speed, and the diffusion of water particles and the range of the atmosphere that was cooled, a result could be drawn from the research that the smaller the diameter of the water vapor gets and the faster the wind speed becomes, the wider the water particles diffuse and the cooler the atmosphere around the fountain becomes. 4) This research further extrapolates that when the ordinary water(tap water, water from river and stream) is used in a fountain, the cooling effect of the air near the fountain can be approached similarly. If the seawater is used in a fountain, there is to be more to concern not only on cooling effect on the air, but also on other effects on surrounding environment generated by the salt in seawater.

Shear strength of compacted soil: effects on splash erosion by single water drops

AbstractThe persistence of soil compaction, caused by farmers' vehicles (tractors wheelings) during the dry season, can affect splash distribution and soil erosion so that surface flow starts at an earlier stage than between the wheelings. To investigate the effects of soil compaction on splash distribution, a dry clayey agricultural soil was compacted in steel cups with a hydraulic piston, and the shear strength was measured with a fall‐cone penetrometer. Two cups were compacted in the same manner, using one to measure the shear strength and the second for splash erosion measurements. A laboratory splash board of 1 m radius, divided into 13 concentric compartments, was used to collect the splashed particles. The water drop diameter used was 4·9 mm falling onto a soil splash cup of 50·2 cm2 area from 8 m height with a terminal velocity of 8·8 m s−1.The spatial distribution of the splashed particles, for different soil compactions, fitted the fundamental splash distribution function (FSDF) model better than the exponential function. The shapes of the curves of this function demonstrated the importance of the source area size; the smaller the cup diameter the better the spatial distribution is expressed by an exponential function. In addition, variability in soil surface conditions contributes to variation in splash characteristics. Detachment rates and average radial distance followed second degree relationships in terms of shear strength. Copyright © 2010 John Wiley &amp; Sons, Ltd.

High-Pressure Water Spray Research Based on Neural Network

The spray cleaning method is important and universal in many industrial processes and other occasion. Because the size of the waterdrop is one of key factors for cleaning, this paper not only studied the relationship between the size of waterdrop and other influencing factors, but also researched the forecasted method for the size of waterdrop. In lab, by measuring the size of the waterdrop, jetted by one kind of nozzle, data were acquired and were used to train the Back Propagation Neural Network ( BPNN ). Through comparing those diameters, between measured in lab and calculated by BPNN after trained. It was acquired that the maximum errors was smaller than 1.62%, between the computed results and the factual measured ones. The experimental results showed that BPNN is an effective tool to predict the variation of the non-linear waterdrop diameter.

W/Oエマルジョンの噴霧燃焼特性に及ぼす油中水滴径の影響(燃焼II,熱工学部門一般講演)

Light oil based oil-in-water emulsion fuels are applied to a direct-injection diesel engine. Fuel consumption and the emission of NOX, HC, CO are measured along with the variation of dispersed waterdrop diameter. As a result, fuel consumption rate decreases as the waterdrop diameter increases. NO_x emissions of the emulsion fuels are lower than of light oil, and are lowered as the waterdrop diameter decreases. HC emission for the emulsion fuel of the largest waterdrop diameter is lower than those for smaller waterdrop diameter emulsions. From the result of the observation of open spray flames, it is considered that those tendencies are the effect of the acceleration of the flame speed caused by microexplosions.

A111 W/O エマルジョン噴霧火炎の燃焼特性に及ぼす分散水滴径の影響

Emulsified fuel combustion is supposed to be effective for the reduction of thermal NO_x and particulate matter. In our previous study, concentration of CO and HC in the exhaust gas decreased as the diameter of the waterdrops in emulsion droplets increased, when we used W/O emulsified fuels for a single cylinder 4-cycle diesel engine. So we examined the effect of waterdrop diameter on exhaust emissions of the diesel engine and microexplosin occurrence. Consequently, concentration of HC and CO decreased for larger waterdrop diameter, and the waterdrop diameter did not influence on the frequency of microexplosion but the special scale of the microexplosions.

Deformation of Interface between a Falling Water Drop and Impacted Oil Surface. Influence of Water Drop Diameter.

The deformation of the interface between a water drop and silicone-oil surface impacted by it was examined in detail. Special attention was directed to the influences of the water-drop diameter dL on the deformation of oil surface and on that of the water drop itself after the impact with the oil surface. The drop diameter was varied from 1.9 mm to 4.1 mm. The influences of dL on the shape of oil cavity at its maximum depth and on the drop shape at its maximum spread were observed conspicuously in case of minimum oil viscosity of vT=5 mm2/s. It was also found that both the maximum cavity depth ratio DM/dL and the maximum diametral deformation ratio dM/dL became smaller as dL was increased. These deformation parameters DM/dL and dM/dL could be well correlated with the impact velocity of drop uL for each oil viscosity. Moreover, in Case B, C and D, DM/dL could be correlated by a dimensionless group ReTLWeTL, and dM/dL was correlated by Re2LOh for highly viscous silicone oil of vT ≥ 5 × 103 mm2/s.

Fog deposition in tall tussock grassland, South Island, New Zealand

Hill cloud microphysics was examined with a forward scattering spectrometer probe over tall tussock grassland at Swampy Summit near Dunedin, New Zealand. In a 4-month period, cloud water drop diameter spectra were obtained for 17 cloud–ground intersection events that varied from 1 to 61 h in duration. Rain fell in most events. Easterly conditions made up 60% of the events and had a median cloud drop diameter of 13.9 μm and 0.14 g m−3 liquid water content. For southwest winds, median drop diameter and liquid water content were significantly smaller at 9.8 μm and 0.05 g m−3.Aerodynamic conductance for momentum transfer, measured with a three-dimensional sonic anemometer, varied linearly with wind speed (R2=0.7) between 50 and 70 mm s−1 for wind speeds from 4 to 9 m s−1. Combining this relation with the cloud liquid water content measurements, cloud water deposition rates were estimated onto the 0.8-m-tall tussock canopy of one-sided leaf area index=3. These estimates were in the range 0.02–0.26 mm h−1 with a median of 0.05 mm h−1 which is the same as the median rate derived from the water balance of a large weighing lysimeter containing eight tussock plants. However, the water balance included a number of small quantities with determination of evaporation and rainfall being particularly difficult. Consequently, the lowest cloud water deposition rates for the water balance were sometimes negative. Nevertheless, even the maximum estimated rates incorporated into an annual calculation suggest cloud water deposition is unlikely to be a significant component of the water balance of a tall tussock grassland catchment. In the uplands of southern New Zealand, changing land use from tall tussock to pastoral agriculture with short vegetation is unlikely to alter streamflows via the cloud water deposition process.

Mechanisms and processes of crust formation on artificial aggregates

Assuming that the degree of aggregate disintegration or stability is affected by the initial moisture conditions, and that the uppermost zone of the soil surface, where a crust is formed, is subjected to the fluctuations of the moisture content under field conditions, the relations among the initial soil moisture conditions, aggregate stability and crust formation should be analyzed in order to elucidate the mechanisms and processes of crusting. Since rainfall is the major factor involved in the disintegration of soil aggregates at the surface through the slaking and impact actions, we determined the degree of aggregate disintegration with slaking and of crusting formed by simulated rainfall treatment as follows; intensity, 4.48 mm min−1; water drop diameter, 2.17 mm; rainfall duration, 2 and 5 min, using artificially granulated aggregates, 1.0 to 2.0 mm in diameter, under moisture conditions preliminarily adjusted at definite levels of matric suction, 0.98 kPa to 9.81 MPa. The results are summarized as follows: 1) Degree of aggregate disintegration and crust development was affected by the initial moisture conditions. 2) Inflection point, where abrupt change of aggregate disintegration occurred, appeared at a certain level of initial matric suction and was designated as critical slaking point (CSP). Above the CSP, the degree of disintegration by slaking was considerable, e.g. the contribution of slaking to the disintegration to the fraction of <0.25 mm in diameter was estimated to be 80% or more for three soils studied. 3) Inflection point of initial matric suction, where the degree of crusting abruptly changed, was designated as critical crusting point (CCP), and it appeared in the wetter range relatively to the CSP. And, 4) initial moisture conditions were divided into three ranges based on the CCP and the CSP. In the wet range of the initial moisture conditions, corresponding to suctions lower than the CCP, no slaking and little crusting occurred, in the dry range, suctions greater than the CSP, slaking and crusting occurred conspicuously, and in the moist range between the CCP and the CSP, crust formation occurred but slaking was hardly observed.

Studies on Plant Response to Rainfall

The present investigation was designed to examine the differences between the effects of rainfall and those of submergence. The growth response and injury of kidney bean plants were examined after the artificial rainfall (mist), root submerging and whole plant submerging treatments. Plants were exposed to mist (Precipitation: 5mm/h, Diameter of water drop: 0.24mm) or submerged in the growth chamber (20°C, 12hr light+12hr dark) for 5 days.(1) Growth response and injury immediately after the treatments:Considerable differences in growth response and injury were observed with the three treatments. In general, the inhibitory effects on growth and injury immediately after the treatments were marked on the shoot by mist, on the root by root submergence and on both the shoot and root by whole plant submergence.Mist treatment decreased the area, dry weight and chlorophyll content of the leaves, but it increased the fresh weight of the stem and elongation of the root (longest root). The greatest wilting response was observed one hour after the end of mist exposure.Root submergence decreased elongation, fresh weight and dry weight of root, but increased the dry weight of the stem. Wilting was not observed.Whole plant submergence decreased markedly elongation, fresh weight of the leaf and root, dry weight of the shoot and root, and chlorophyll content of the leaf. Wilting was observed, but its degree was weaker than that of mist.(2) Growth response and injury 12 days after the treatments:Mist treatment caused growth inhibition, but the degree of inhibition was weaker than that immediately after the treatments. The aftereffect of mist remained on fresh weight of leaf and dry weight of shoot and root to some extent. Foliage leaves that opened after mist treatment were injured strikingly.Root submergence decreased root length, leaf area, fresh weight (leaf, stem) and dry weight (shoot, root) to some extent, but foliage leaves were not injured.Whole plant submergence decreased elongation, fresh weight and dry weight of shoot and root to a great extent. Foliage leaves were injured, but less severely than by mist.These results suggest that the exposure to rainfall not only causes weak effects of submergence, but also has a different action on the plant.

Studies on Plant Response to Rainfall.

The present investigation was designed to examine the differences between the effects of rainfall and those of submergence. The growth response and injury of kidney bean plants were examined after the artificial rainfall (mist), root submerging and whole plant submerging treatments. Plants were exposed to mist (Precipitation: 5mm/h, Diameter of water drop: 0.24mm) or submerged in the growth chamber (20°C, 12hr light+12hr dark) for 5 days.(1) Growth response and injury immediately after the treatments:Considerable differences in growth response and injury were observed with the three treatments. In general, the inhibitory effects on growth and injury immediately after the treatments were marked on the shoot by mist, on the root by root submergence and on both the shoot and root by whole plant submergence.Mist treatment decreased the area, dry weight and chlorophyll content of the leaves, but it increased the fresh weight of the stem and elongation of the root (longest root). The greatest wilting response was observed one hour after the end of mist exposure.Root submergence decreased elongation, fresh weight and dry weight of root, but increased the dry weight of the stem. Wilting was not observed.Whole plant submergence decreased markedly elongation, fresh weight of the leaf and root, dry weight of the shoot and root, and chlorophyll content of the leaf. Wilting was observed, but its degree was weaker than that of mist.(2) Growth response and injury 12 days after the treatments:Mist treatment caused growth inhibition, but the degree of inhibition was weaker than that immediately after the treatments. The aftereffect of mist remained on fresh weight of leaf and dry weight of shoot and root to some extent. Foliage leaves that opened after mist treatment were injured strikingly.Root submergence decreased root length, leaf area, fresh weight (leaf, stem) and dry weight (shoot, root) to some extent, but foliage leaves were not injured.Whole plant submergence decreased elongation, fresh weight and dry weight of shoot and root to a great extent. Foliage leaves were injured, but less severely than by mist.These results suggest that the exposure to rainfall not only causes weak effects of submergence, but also has a different action on the plant.

Splash Droplet Production by Waterdrop Impact

Splash droplets produced by waterdrop impact were described by the normal distribution parameters derived on a volume basis. The major splash variables of surface water depth d and waterdrop diameter D were examined by using the distribution parameters: D50, the droplet diameter when 50% of the splash volume consists of larger droplets; σ, the standard deviation; and N, the number of droplets produced by one waterdrop impact. For a waterdrop diameter of 0.4 cm, D50 was about 0.04 cm near zero depth, reached a maximum size of 0.15 cm at d/D = 0.5, and then decreased to a constant size of less than 0.13 cm for d/D &gt; 3. Larger waterdrops produced larger splash droplets.

Splash Amounts from Waterdrop Impact on a Smooth Surface

The mechanics of raindrop splash erosion of soil were investigated by using waterdrops impacting at terminal velocity onto various depths of water over smooth glass. Splash weight produced by waterdrop impact varied with waterdrop diameter D and surface water depth d. For a smooth hard surface, predicted splash in terms of waterdrop weight was zero at d/D = 0 and increased to a maximum at d/D of 0.14 and 0.20 for D = 0.559 cm and 0.296 cm, respectively. The influence of greater depth became relatively insignificant at a depth of about three drop diameters.

Swept frequency measurement of water-drop diameter

Swept frequency measurement of water-drop diameter