Letter: Dome-shaped splashes generated by the impact of a small disk on a sessile water drop

2018 ◽  
Vol 30 (10) ◽  
pp. 101702 ◽  
Author(s):  
A. V. Bazilevsky ◽  
A. N. Rozhkov
Keyword(s):  
Water Drop ◽  
Small Disk ◽  
The Impact

scholarly journals Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 691
Author(s):  
Yugang Zhao ◽  
Zichao Zuo ◽  
Haibo Tang ◽  
Xin Zhang
Keyword(s):  
Vapor Pressure ◽  
Substrate Temperature ◽  
Water Drop ◽  
Industrial Processes ◽  
Aircraft Icing ◽  
Ice Coverage ◽  
Fundamental Understanding ◽  
Order Of Magnitude ◽  
The Impact ◽  
Kinetics Of

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

Splash formation by spherical drops

2001 ◽  
Vol 427 ◽  
pp. 73-105 ◽  
Author(s):  
LIOW JONG LENG
Keyword(s):  
High Resolution ◽  
Quantitative Data ◽  
Water Surface ◽  
High Speed ◽  
Scaling Laws ◽  
Capillary Wave ◽  
Water Drop ◽  
Qualitative And Quantitative ◽  
High Resolution Images ◽  
The Impact

The impact of a spherical water drop onto a water surface has been studied experimentally with the aid of a 35 mm drum camera giving high-resolution images that provided qualitative and quantitative data on the phenomena. Scaling laws for the time to reach maximum cavity sizes have been derived and provide a good fit to the experimental results. Transitions between the regimes for coalescence-only, the formation of a high-speed jet and bubble entrapment have been delineated. The high-speed jet was found to occur without bubble entrapment. This was caused by the rapid retraction of the trough formed by a capillary wave converging to the centre of the cavity base. The converging capillary wave has a profile similar to a Crapper wave. A plot showing the different regimes of cavity and impact drop behaviour in the Weber–Froude number-plane has been constructed for Fr and We less than 1000.

Collisions between liquid drops

1978 ◽  
Vol 287 (1349) ◽  
pp. 635-675 ◽  
Keyword(s):  
Simple Model ◽  
Impact Parameter ◽  
Water Drop ◽  
Free Fall ◽  
Electrostatic Energy ◽  
Good Effect ◽  
Frequency Distributions ◽  
Input Parameters ◽  
The Impact ◽  
Drop Charge

An experiment is described in which pairs of water drops of different size were caused to collide during free fall at a velocity equal to the difference of their terminal velocities in still air. The collision parameters of trajectory, drop size, and drop charge were controlled with precision, and impacts of a particular kind could be reproduced indefinitely. By using synchronized flash photography, well in excess of 30000 measurements were taken from more than 10000 frames of film of the resulting behaviour of the water-drop pairs. Data are discussed in terms of an impact parameter, X which defines the relative trajectory of the drops in the centre-of-mass frame, and three energy parameters e C , e R and e T which delineate the properties electrostatic energy, rotational energy, and total energy of the two-drop system before impact. Input parameters were confined to values appropriate to natural rainfall. After collision four basic types of rotation occurred, the particular kind of rotation depending upon X , e C , e R and e T . Measured rates of rotation were compared with that to be expected from a simple model of inelastic collision between solid spheres and showed a marked resemblance. Distributions of mass after collision were compared with a model based upon a bimodal Gaussian distribution to good effect. In addition, frequency distributions of the number of drop products resulting from a given collision were prepared showing the controlling influence of the impact parameter, X , and the effect of varying drop charge. Relations were also established between statistical values for the coalescence efficiency of a given drop pair and the input parameters; however, while all results were consistent and reproducible, the effect of drop charge could not be demonstrated by a simple model.

scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

Effect of secondary succession in abandoned fields on some properties of acidic sandy soils

2020 ◽  
Author(s):  
Peter Surda ◽  
Lubomir Lichner ◽  
Viliam Nagy
Keyword(s):  
Pore Size ◽  
Secondary Succession ◽  
Water Drop ◽  
Sandy Soils ◽  
Water Repellency ◽  
Organic Carbon Content ◽  
Abandoned Fields ◽  
Water Sorptivity ◽  
The Impact ◽  
Penetration Time

<p>Abandonment of agricultural lands in recent decades is occurring mainly in Europe, North America and Oceania, and changing the fate of landscapes as the ecosystem recovers during fallow stage. The objective of this study was to find the impact of secondary succession in abandoned fields on some parameters of acidic sandy soils in the Borská nížina lowland (southwestern Slovakia). We investigated soil chemical (pH and soil organic carbon content), hydrophysical (water sorptivity, and hydraulic conductivity), and water repellency (water drop penetration time, water repellency cessation time, repellency index, and modified repellency index) parameters, as well as the ethanol sorptivity of the studied soils. Both the hydrophysical and chemical parameters decreased significantly during abandonment of the three investigated agricultural fields. On the other hand, the water repellency parameters increased significantly, but the ethanol sorptivity did not change during abandonment. As the ethanol sorptivity depends mainly on soil pore size, the last finding could mean that the pore size of acidic sandy soils did not change during succession.</p>

Pressure Gage Measurements in a Dry to Wet Environment

2009 ◽  
Author(s):  
Anne M. Fullerton ◽  
Thomas C. Fu
Keyword(s):  
Gate Valve ◽  
Water Drop ◽  
Water Pressure ◽  
Pressure Sensors ◽  
Pressure Rise ◽  
Thermal Drift ◽  
Wave Impact ◽  
Unique Problem ◽  
Pressure Gage ◽  
The Impact

Pressure gages are used in many fluid measurements applications. One such application is the measurement of wave impact pressures on structures. This application poses a unique problem of measuring pressures in a “wet to dry” environment. Often there is a thermal drift component in the pressure readings that makes it difficult to extract the actual pressure rise due to wave loading. These types of measurements also require high response rates to measure the detail of the short duration impacts, usually on the order of one to twenty kilohertz. Several bench tests were carried out in at the Naval Surface Warfare Center, Carderock Division, in 2008 to investigate various types of gages to find a robust gage that could withstand this type of application. Three different gages were used in this investigation. The first sensor (gage 1) is a dynamics general purpose ICP (integrated circuit piezoelectric) pressure sensor, capable of making very high frequency dynamic pressure measurements, rated to 200 psi. The second sensor (gage 2) is a voltage compensated, media isolated piezoresistive sensor, rated to 15 psi. This gage had a pressure port which was filled with water during testing to eliminate air compression effects. The third sensor (gage 3) is a semiconductor pressure gage rated to 25 psi (172.4 kPa). A water “drop” test setup was constructed of 2 inch (5.1 cm) PVC pipe. The pressure gages were mounted to the bottom of the setup facing up, and the pipe was filled from the top, with a quick acting gate valve located 2 feet (0.61 m) from the pressure sensors. Once the pipe was filled with the desired amount of water, the gate valve was opened as quickly as possible, and the impact force was measured. Vent pipes were mounted to a “cross” fitting in the vertical pipe which allowed for the air to escape. Several water “drop” tests were performed with this setup. From these tests, the thermal drift of gage 1 is evident. Gage 3 exhibits similar behavior. Gage 2 captures the water pressure impact, and then returns to a small positive static pressure as a result of the water that is sitting above it. Of the three sensors, gage 2 appears to be the most temperature stable.

An experimental investigation of fluid flow resulting from the impact of a water drop with an unyielding dry surface

1981 ◽  
Vol 373 (1755) ◽  
pp. 419-441 ◽  
Keyword(s):  
Water Drop ◽  
Roughness Parameter ◽  
Fluid Velocities ◽  
Spatial Dimensions ◽  
Water Drops ◽  
The Moment ◽  
High Degree ◽  
First Contact ◽  
The Impact

The flow of fluid associated with the impact of water drops of radius R at a speed V onto unyielding dry metal surfaces of known roughness R a is described. Spatial dimensions of the deforming drop are normalized by transformations of the kind x ' — x/R , and time scales are normalized according to t ' = tV/R , to permit comparison of events where or differ. It is shown that the primary influence of the surface roughness parameter R a is the determination of the condition for the ejection of secondary droplets by the excitation of an instability in the developing watersheet; provided R a ≪ R , it is possible to evaluate the condition to a high degree of accuracy, and for R a = 0.84 μm it is found to be α4/3 RV 1.69 > 7.4, where α is the eccentricity of the drop at the moment of impact. Deceleration of the drop apex does not commence until > 0.6, contrary to the prediction of Engel (1955) but in good agreement with that of Savic & Boult (1957). Close examination of the very early stages of impact suggests strongly that the so-called watersheet originates at a moment t ' — 0.01 after first contact, regardless of the absolute values of R, V or R a ; the initial normalized watersheet velocity is of order 5. Where there is ejected material, its normalized velocity at the moment of ejection is of the order of 20 % greater than that of the watersheet substrate. Simple calculations also suggest that initial fluid velocities greater than 10 are required immediately before the initiation of the watersheet ( t '< 0.01). Impacts at speeds considerably greater than the appropriate terminal fall speed in air show no deviations in character from those investigated at much lower speeds. A simple subsidiary experiment also suggests that greater impact velocities are required to produce splashing on inclined targets.

Wildfire effects on soil carbon and water repellency under eucalyptus forest in Eastern Australia

Soil Research ◽  
2015 ◽  
Vol 53 (1) ◽  
pp. 13 ◽  
Author(s):  
Jessica T. Heath ◽  
Chris J. Chafer ◽  
Thomas F. A. Bishop ◽  
Floris F. Van Ogtrop
Keyword(s):  
Soil Properties ◽  
Soil Carbon ◽  
Water Drop ◽  
Water Repellency ◽  
Total Carbon ◽  
Burn Severity ◽  
Eucalyptus Forest ◽  
Eastern Australia ◽  
Study Sites ◽  
The Impact

Soil properties can be considerably modified as a result of wildfire. This study examined the impact of wildfire on total carbon and water repellency at two study sites, namely Cranebrook and Wentworth Falls, located 45 and 75 km west of Sydney, Australia, respectively. Within each study site, we measured soil properties at two depth intervals from five burn severity classes along 15 transects (10 sample points per transect). Samples were taken 6, 12 and 36 months after wildfire. Soil total carbon was measured using LECO combustion analysis and potential soil water repellency was determined using water drop penetration time. Two-way analysis of variance (ANOVA) was used to analyse the results, with burn severity and time as factors. Burn severity had a significant effect on both soil total carbon and water repellency at both study sites, whereas time was only significant for soil carbon at Wentworth Falls. Soil total carbon and water repellency were variable through time due to local environmental variables, such as rainfall and temperature. The relationship between soil total carbon and water repellency was strong for Cranebrook in the surface soil (r = 0.62) and lower in the subsurface soil (r = 0.41), but weaker at Wentworth Falls, with values of r = 0.22 and r = 0.15 in the surface and subsurface soils respectively.

scholarly journals Small-Scale Drop Size Variability: Impact on Estimation of Cloud Optical Properties

2005 ◽  
Vol 62 (7) ◽  
pp. 2555-2567 ◽  
Author(s):  
Y. Knyazikhin ◽  
R. B. Myneni ◽  
A. Marshak ◽  
W. J. Wiscombe ◽  
M. L. Larsen ◽  
...  
Keyword(s):  
Drop Size ◽  
Water Drop ◽  
Small Scale ◽  
Size Dependent ◽  
Radiative Impact ◽  
Size Variability ◽  
The Mean ◽  
Conventional Models ◽  
Processing Techniques ◽  
The Impact

Abstract Most cloud radiation models and conventional data processing techniques assume that the mean number of drops of a given radius is proportional to volume. The analysis of microphysical data on liquid water drop sizes shows that, for sufficiently small volumes, this proportionality breaks down; the number of cloud drops of a given radius is instead proportional to the volume raised to a drop size–dependent nonunit power. The coefficient of proportionality, a generalized drop concentration, is a function of the drop size. For abundant small drops the power is unity as assumed in the conventional approach. However, for rarer large drops, it falls increasingly below unity. This empirical fact leads to drop clustering, with the larger drops exhibiting a greater degree of clustering. The generalized drop concentration shows the mean number of drops per cluster, while the power characterizes the occurrence frequency of clusters. With a fixed total number of drops in a cloud, a decrease in frequency of clusters is accompanied by a corresponding increase in the generalized concentration. This initiates a competing process missed in the conventional models: an increase in the number of drops per cluster enhances the impact of rarer large drops on cloud radiation while a decrease in the frequency suppresses it. Because of the nonlinear relationship between the number of clustered drops and the volume, these two opposite tendencies do not necessarily compensate each other. The data analysis suggests that clustered drops likely have a stronger radiative impact compared to their unclustered counterpart; ignoring it results in underestimation of the contribution from large drops to cloud horizontal optical path.

scholarly journals Drop Impact on Textile Material: Effect of Fabric Properties

2014 ◽  
Vol 14 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Zouhaier Romdhani ◽  
Ayda Baffoun ◽  
Mohamed Hamdaoui ◽  
Sadok Roudesli
Keyword(s):  
Water Drop ◽  
Free Fall ◽  
Spreading Rate ◽  
Drop Impact ◽  
Drop Deformation ◽  
Coating Film ◽  
Drop Shape ◽  
Coated Fabric ◽  
Fabric Construction ◽  
The Impact

Abstract This paper presents an experimental study of impact of water drop on a surface in a spreading regime with no splashing. Three surfaces were studied: virgin glass, coating film and woven cotton fabric at different construction parameters. All experiments were carried out using water drop with the same free fall high. Digidrop with high-resolution camera is used to measure the different parameters characterising this phenomenon. Results show an important effect of the height of the free fall on the drop profile and the spreading behaviour. An important drop deformation at the surface impact was observed. Then, fabric construction as the weft count deeply affects the drop impact. For plain weave, an increase of weft count causes a decrease in penetration and increase in the spreading rate. The same result was obtained for coated fabric. Therefore, the impact energy was modified and the drop shape was affected, which directly influenced the spreading rate.

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