Dynamics of water drop detachment from a superhydrophobic surface induced by an ultrasonic field

2018 ◽  
Vol 124 (16) ◽  
pp. 164905
Author(s):  
D. L. Geng ◽  
L. Hu ◽  
Z. Y. Hong ◽  
W. J. Xie ◽  
B. Wei
Keyword(s):  
Superhydrophobic Surface ◽  
Water Drop ◽  
Ultrasonic Field ◽  
Drop Detachment

scholarly journals Research of freezing kinetics of water drop on superhydrophobic coating surfaces

Vestnik MGSU ◽  
2019 ◽  
pp. 435-441
Author(s):  
About the author: Valentina I. Loganina
Keyword(s):  
Temperature Distribution ◽  
Superhydrophobic Surface ◽  
Water Drop ◽  
Initial Period ◽  
Technical Problem ◽  
Superhydrophobic Surfaces ◽  
Silicone Resin ◽  
Thermal Imager ◽  
Upward Movement ◽  
Kinetics Of

Introduction. Anti-icing coatings are used to prevent icing of the building roofs and power transmission line poles. One of the characteristics of anti-icing properties of superhydrophobic surfaces is the delay in the crystallization of drops on such surfaces. A significant delay in the crystallization of water drops on superhydrophobic substrates is noted in the scientific and technical literature. However, it is recorded in a number of papers that the delay time of crystallization on hydrophilic substrates is longer than the corresponding values on superhydrophobic surfaces. In connection with the foregoing, the study of the freezing kinetics of a water drop on a superhydrophobic surface in order to assess its efficiency is a relevant scientific and technical problem. Materials and methods. To evaluate the kinetics of freezing a of water drop on a superhydrophobic surface, the following experiment is conducted. A drop of water is placed on the superhydrophobic surface of the mortar substrate, which is placed in a freezer at a temperature of –18 °C. Studies of the drop freezing dynamics on the surface are performed using a Testo 875-1 thermal imager. To create a superhydrophobic surface, an aerosil R 972 with density ρ = 2360 kg/m3, particle size of 16 nm and specific surface area Ssp = 12 000 m2/kg is used as a filler. A silicone resin SILRES® MSE 100 of 10 % concentration is used as a binder. The obtained solutions are deposited on the mortar substrates. The degree of hydrophobicity is assessed by the magnitude of the wetting angle (θ°). Results. Results of the studies of temperature distribution on the water drop surface indicate that the distribution is uneven. The process of drop freezing is multistage. In the initial period, there is a transfer of heat from the surface into the water drop. This stage is followed by the process of drop freezing which is manifested in the upward movement of the freezing front from the substrate. Conclusions. It is revealed that the temperature distribution on the surface of a water drop is uneven. When freezing, a water drop has a pointed top.

scholarly journals Trapping a Hot Drop on a Superhydrophobic Surface with Rapid Condensation or Microtexture Melting

Micromachines ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 566 ◽  
Author(s):  
Samira Shiri ◽  
Armela Murrizi ◽  
James Bird
Keyword(s):  
Critical Temperature ◽  
Superhydrophobic Surface ◽  
Water Drop ◽  
Superhydrophobic Surfaces ◽  
Temperature Threshold ◽  
New Class ◽  
Condensation Growth ◽  
Thermal Fuse ◽  
Impact Experiments ◽  
Insight Into

A water drop can bounce upon impacting a superhydrophobic surface. However, on certain superhydrophobic surfaces, a water drop will stick rather than bounce if it is sufficiently hot. Here, we aim to better understand the mechanisms that can lead to this bouncing-sticking transition. Specifically, we model two potential mechanisms in which a superhydrophobic surface could trap a sufficiently hot drop within milliseconds: melting of microtextured wax and condensation of the vapor within the superhydrophobic texture. We then test these mechanisms through systematic drop impact experiments in which we independently vary the substrate and drop temperatures on a waxy superhydrophobic Nasturtium leaf. We find that, whenever the surface or the drop is above a microtexture-melting temperature, the drop sticks. Below this temperature, a critical temperature threshold for bouncing can be predicted and controlled by considering the relative timescales between condensation growth and drop residence time. We envision that these results can provide insight into the design of a new class of superhydrophobic surfaces to act as a rapid thermal fuse to prevent drops that exceed a critical temperature from bouncing onto a thermally sensitive target.

Nonlinear dynamics of a shell encapsulated microbubble near solid boundary in an ultrasonic field

2020 ◽  
Vol 14 (3) ◽  
pp. 7235-7243
Author(s):  
N.M. Ali ◽  
F. Dzaharudin ◽  
E.A. Alias
Keyword(s):  
Oscillation Amplitude ◽  
Ultrasonic Field ◽  
Dynamical Behaviour ◽  
Ultrasound Contrast Agents ◽  
Chaotic Behaviour ◽  
Solid Boundary ◽  
Driving Frequency ◽  
Pressure Amplitude ◽  
Radial Expansion ◽  
Therapeutic Delivery

Microbubbles have the potential to be used for diagnostic imaging and therapeutic delivery. However, the transition from microbubbles currently being used as ultrasound contrast agents to achieve its’ potentials in the biomedical field requires more in depth understanding. Of particular importance is the influence of microbubble encapsulation of a microbubble near a vessel wall on the dynamical behaviour as it stabilizes the bubble. However, many bubble studies do not consider shell encapsulation in their studies. In this work, the dynamics of an encapsulated microbubble near a boundary was studied by numerically solving the governing equations for microbubble oscillation. In order to elucidate the effects of a boundary to the non-linear microbubble oscillation the separation distances between microbubble will be varied along with the acoustic driving. The complex nonlinear vibration response was studied in terms of bifurcation diagrams and the maximum radial expansion. It was found that the increase in distance between the boundary and the encapsulated bubble will increase the oscillation amplitude. When the value of pressure amplitude increased the single bubble is more likely to exhibit the chaotic behaviour and maximum radius also increase as the inter wall-bubble distance is gradually increased. While, with higher driving frequency the maximum radial expansion decreases and suppress the chaotic behaviour.

Воздействиеультразвуковогополянадинамическуювязкостьводы

2019 ◽  
pp. 27-29
Author(s):  
P. Vikulin ◽  
K. Khlopov ◽  
M. Cherkashin
Keyword(s):  
Dynamic Viscosity ◽  
Experimental Studies ◽  
Ultrasonic Field ◽  
Maximum Effect ◽  
Ultrasonic Frequency ◽  
Ultrasonic Vibrations ◽  
Wastewater Disposal ◽  
Laboratory Setup ◽  
Sonic Treatment ◽  
The Impact

Enhancing water purification processes is provided by various methods including physical ones, in particular, exposure to ultrasonic vibrations. The change in the dynamic viscosity of water affects the rate of deposition of particles in the aquatic environment which can be used in natural and wastewater treatment. At the Department Water Supply and Wastewater Disposal of the National Research Moscow State University of Civil Engineering experimental studies were conducted under laboratory conditions to study the effect of ultrasound on the change in the dynamic viscosity of water. A laboratory setup has been designed consisting of an ultrasonic frequency generator of the relative intensity, a transducer (concentrator) that transmits ultrasonic vibrations to the source water, and sonic treatment tanks. Experimental studies on the impact of the ultrasonic field in the cavitation mode on the dynamic viscosity of the aqueous medium were carried out the exposure time was obtained to achieve the maximum effect.Интенсификация процессов очистки воды осуществляется с помощью различных методов, в том числе и физических, в частности воздействием ультразвуковых колебаний. Изменение динамической вязкости воды влияет на скорость осаждения частиц в водной среде, что может быть использовано в процессах очистки природных и сточных вод. На кафедре Водоснабжение и водоотведение Национального исследовательского Московского государственного строительного университета в лабораторных условиях проведены экспериментальные исследования по изучению влияния ультразвука на изменение динамической вязкости воды. Разработана схема лабораторной установки, состоящая из генератора ультразвуковых частот с соответствующей интенсивностью, преобразователя (концентратора), передающего ультразвуковые колебания в исходную воду, и емкости для озвучивания. Выполнены экспериментальные исследования по влиянию ультразвукового поля в режиме кавитации на динамическую вязкость водной среды, получено время экспозиции для достижения максимального эффекта.

Corrosion Resistance of Ni-CeO2 Nanocomposite Coatings Prepared by Pulse Electrodeposition in an Ultrasonic Field

2010 ◽  
Vol 25 (5) ◽  
pp. 522-526
Author(s):  
Yu-Jun XUE ◽  
Hong-Bin LIU ◽  
Ming-Ming LAN ◽  
Hong-Biao HAN ◽  
Ji-Shun LI
Keyword(s):  
Corrosion Resistance ◽  
Ultrasonic Field ◽  
Pulse Electrodeposition ◽  
Nanocomposite Coatings

Antimicrobial Activity of Silver Nanoparticles Prepared Under an Ultrasonic Field

2011 ◽  
Vol 4 (3) ◽  
pp. 1491-1496
Author(s):  
Umadevi M ◽  
Rani T ◽  
Balakrishnan T ◽  
Ramanibai R
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Silver Nanoparticles ◽  
Reduction Method ◽  
Therapeutic Potential ◽  
Chemical Reduction ◽  
Ultrasonic Field ◽  
Great Promise ◽  
Chemical Reduction Method ◽  
E Coli

Nanotechnology has great promise for improving the therapeutic potential of medicinal molecules and related agents. In this study, silver nanoparticles of different sizes were synthesized in an ultrasonic field using the chemical reduction method with sodium borohydride as a reducing agent. The size effect of silver nanoparticles on antimicrobial activity were tested against the microorganisms Staphylococcus aureus (MTCC No. 96), Bacillus subtilis (MTCC No. 441), Streptococcus mutans (MTCC No. 497), Escherichia coli (MTCC No. 739) and Pseudomonas aeruginosa (MTCC No. 1934). The results shows that B. subtilis, and E. coli were more sensitive to silver nanoparticles and its size, indicating the superior antimicrobial efficacy of silver nanoparticles. 

Reply to “Comments on ‘Energy Dissipation During Water Drop Impact In Shallow Pools’”

1986 ◽  
Vol 50 (6) ◽  
pp. 1644-1645
Author(s):  
Alfredo G. Ferreira ◽  
Bruce E. Larock ◽  
Michael J. Singer
Keyword(s):  
Energy Dissipation ◽  
Water Drop ◽  
Drop Impact

Changes of some sewage sludge parameters prepared with an ultrasonic field

1997 ◽  
Vol 36 (11) ◽  
pp. 101-106 ◽  
Author(s):  
January Bien ◽  
Lidia Wolny
Keyword(s):  
Sewage Sludge ◽  
Microscopic Analysis ◽  
Chemical Compounds ◽  
Ultrasonic Field ◽  
Water Removal ◽  
Vacuum Filter ◽  
Additional Criterion ◽  
New Methods ◽  
Sludge Conditioning

Studies of sewage sludge conditioning by ultrasonic field concentrate on determination of the increase of water removal effect, which depends on kind of sludge and chemical compounds used in the dewatering process. An attempt was made to find new methods of sludge preparation before dewatering. Tests presented here focused on digested and difficult dewatered sludge. The sludge was dewatered on a vacuum filter after conditioning with polyelectrolytes and the ultrasonic field. The microscopic analysis was an additional criterion to evaluate changes in the sludge structure after preparation. The polyelectrolyte dose of 3 mg/g d.m. sonicated within 15 sec. resulted in the 50% decrease of sludge volume. Results presented confirmed our previous experiences, concerning the relation between conglomerates of sludge and the effect of dewatering.

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