Impact of a small disk on a sessile water drop

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.

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Spreading and Drying Dynamics of Water Drop on Hot Surface of Superwicking Ti-6Al-4V Alloy Material Fabricated by Femtosecond Laser

Nanomaterials ◽

10.3390/nano11040899 ◽

2021 ◽

Vol 11 (4) ◽

pp. 899

Author(s):

Ranran Fang ◽

Zekai Li ◽

Xianhang Zhang ◽

Xiaohui Zhu ◽

Hanlin Zhang ◽

...

Keyword(s):

Femtosecond Laser ◽

Surface Structure ◽

Energy Savings ◽

Water Drop ◽

Capillary Surface ◽

Water Flow Velocity ◽

Capillary Action ◽

Practical Applications ◽

Alloy Material ◽

Hot Surface

A superwicking Ti-6Al-4V alloy material with a hierarchical capillary surface structure was fabricated using femtosecond laser. The basic capillary surface structure is an array of micropillars/microholes. For enhancing its capillary action, the surface of the micropillars/microholes is additionally structured by regular fine microgrooves using a technique of laser-induced periodic surface structures (LIPSS), providing an extremely strong capillary action in a temperature range between 23 °C and 80 °C. Due to strong capillary action, a water drop quickly spreads in the wicking surface structure and forms a thin film over a large surface area, resulting in fast evaporation. The maximum water flow velocity after the acceleration stage is found to be 225–250 mm/s. In contrast to other metallic materials with surface capillarity produced by laser processing, the wicking performance of which quickly degrades with time, the wicking functionality of the material created here is long-lasting. Strong and long-lasting wicking properties make the created material suitable for a large variety of practical applications based on liquid-vapor phase change. Potential significant energy savings in air-conditioning and cooling data centers due to application of the material created here can contribute to mitigation of global warming.

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Strain-dependent wicking behavior of cotton/lycra elastic woven fabric for sportswear

e-Polymers ◽

10.1515/epoly-2021-0030 ◽

2021 ◽

Vol 21 (1) ◽

pp. 263-271

Author(s):

Yong Wang ◽

Qifan Qiao ◽

Zuowei Ding ◽

Fengxin Sun

Keyword(s):

Tensile Strain ◽

Water Drop ◽

Woven Fabric ◽

Strengthening Effect ◽

Wetting Time ◽

Horizontal Wicking ◽

Different Strains ◽

Strain Dependent ◽

Different Levels ◽

Strain Strengthening

Abstract The strain-dependent vertical and horizontal wicking of as-prepared cotton/lycra elastic woven fabric was systematically studied. The experimental results revealed that the fabric exhibited a strain strengthening effect. A higher tensile strain results in a higher equilibrium wicking height, and vice versa. Moreover, the results indicated that the proposed Laughlin–Davies model is capable of tracking well the experimental data and replicating the wicking characteristics of fabric under different levels of stretch. In addition, the wetting time and wicking area of fabric under different strains and height regimes were examined during horizontal wicking. It was found that the wetting time decreased with an increase of strain and/or water drop height. The strain-enhanced and height-weakened effects of wicking area were revealed. The spreading mechanism of water drop in elastic fabric was also proposed. Such fundamental work provides a basic support for the in-depth investigation of wicking behavior of complex stretchable textile structures.

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A Water-Drop Method of Hardening of the Welded Joints of Drill Pipes

Metal Science and Heat Treatment ◽

10.1007/s11041-015-9878-2 ◽

2015 ◽

Vol 57 (5-6) ◽

pp. 295-299

Author(s):

M. V. Maisuradze ◽

Yu. V. Yudin ◽

Yu. G. Eismondt

Keyword(s):

Welded Joints ◽

Water Drop ◽

Drop Method ◽

Drill Pipes

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Soil water repellency persistence after recurrent forest fires on Mount Carmel, Israel

International Journal of Wildland Fire ◽

10.1071/wf12063 ◽

2013 ◽

Vol 22 (4) ◽

pp. 515 ◽

Cited By ~ 19

Author(s):

Naama Tessler ◽

Lea Wittenberg ◽

Noam Greenbaum

Keyword(s):

Organic Matter ◽

Soil Water ◽

Forest Fires ◽

Water Drop ◽

Chemical Properties ◽

Water Repellency ◽

Mediterranean Ecosystem ◽

Long Term Effects ◽

Soil Water Repellency ◽

Chemical Properties Of Soils

Variations in forest fires regime affect: (1) the natural patterns of community structure and vegetation; (2) the physico-chemical properties of soils and consequently (3) runoff, erosion and sediment yield. In recent decades the Mediterranean ecosystem of Mount Carmel, north-western Israel, is subjected to an increasing number of forest fires, thus, the objectives of the study were to evaluate the long-term effects of single and recurrent fires on soil water repellency (WR) and organic matter (OM) content. Water repellency was studied by applying water drop penetration time (WDPT) tests at sites burnt by single-fire, two fires, three fires and unburnt control sites. Water repellency in the burnt sites was significantly lower than in the unburnt control sites, and the soil maintained its wettability for more than 2 decades, whereas after recurrent fires, the rehabilitation was more complicated and protracted. The OM content was significantly lower after recurrent than after a single fire, causing a clear proportional decrease in WR. The rehabilitation of WR to natural values is highly dependent on restoration of organic matter and revegetation. Recurrent fires may cause a delay in recovery and reduced productivity of the soil for a long period.

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Observations on the Steady-State Solution of an Extremely Flexible Spinning Disk With a Transverse Load

Journal of Applied Mechanics ◽

10.1115/1.3167085 ◽

1983 ◽

Vol 50 (3) ◽

pp. 525-530 ◽

Cited By ~ 14

Author(s):

R. C. Benson

Keyword(s):

Steady State ◽

Hybrid System ◽

Fourth Order ◽

Steady State Solution ◽

Transverse Load ◽

System Of Differential Equations ◽

Membrane Theory ◽

Small Disk ◽

Spinning Disk ◽

Flexible Disk

The steady deflection of a transversely loaded, extremely flexible, spinning disk is studied. Membrane theory is used to predict the shapes and locations of waves that dominate the response. It is found that waves in disconnected regions are possible. Some results are presented to show how disk stiffness moderates the membrane waves, the most important result being an upper bound on the highest ordered wave of significant amplitude. A hybrid system of differential equations and boundary conditions is developed to replace the pure membrane formulation that is singular, and the full fourth-order plate formulation that is numerically sensitive. The hybrid formulation retains the salient features of the flexible disk response and facilitates calculations for very small disk stiffnesses.

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