scholarly journals Spreading dynamics of liquid droplet on gradient micro-structured surfaces

2015 ◽  
Vol 64 (15) ◽  
pp. 154705
Author(s):  
Lin Lin ◽  
Yuan Ru-Qiang ◽  
Zhang Xin-Xin ◽  
Wang Xiao-Dong
Keyword(s):  
Liquid Droplet ◽  
Structured Surfaces ◽  
Spreading Dynamics

Numerical Investigation of a Liquid Droplet Impinging on a Heated Surface

2009 ◽  
Author(s):  
Andres Diaz ◽  
Alfonso Ortega ◽  
Ryan Anderson
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Fundamental Problem ◽  
Water Drop ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Heat Removal ◽  
Droplet Spreading ◽  
Droplet Shape ◽  
Spreading Dynamics

Previous studies, most of them experimental, reveal that the cooling effectiveness of a water drop impinging on a heated surface depends on the wall temperature, droplet shape and velocity. All previous studies focus on the behavior of a droplet falling in a quiescent environment, such as still air. Evidence in the literature also shows that gas assisted droplet sprays, in which a gas phase propels the droplets, are more efficient in heat removal than sprays consisting of droplets alone. It is conjectured that this is due to an increase in the maximum droplet spreading diameter upon impact, a thinner film, and consequently an increase in the overall heat transfer coefficient. Recent experiments in the author’s group [1, 2] show that the carrier gas jet strongly influences droplet spreading dynamics by imposing normal and shear forces on the liquid surface. The heat transfer is greatly augmented in the process, compared to a free falling droplet. To date, there has been no fundamental investigation of the physics of gas assisted spray cooling. To begin to understand the complicated process, this paper reports on a fundamental problem of a single liquid droplet that impinges on a heated surface. This paper contributes a numerical investigation of the problem using the volume of fluid (VOF) technique to capture droplet spreading dynamics and heat transfer in a single drop event. The fluid mechanics is investigated and compared to the experimental data. The greatest uncertainty in the simulation is in the specification of the contact angle of the advancing or receding liquid front, and in capturing the onset of the three-dimensional fingering phenomena.

Dynamics of a Water Droplet on the Heated Surface of Nano- and Micro-Structures

2012 ◽  
Author(s):  
Seol Ha Kim ◽  
Ho Seon Ahn ◽  
Joonwon Kim ◽  
Moo Hwan Kim
Keyword(s):  
Water Droplet ◽  
High Speed ◽  
Zirconium Alloy ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Complete Wetting ◽  
Structured Surfaces ◽  
Bare Surface

In this study, we investigated the dynamic behavior of a water droplet near the Leidenfrost point (LFP) of bare and modified zirconium alloy surfaces with bundles of nanotubes (∼10–100 nm) or micro mountain-like structures using high-speed photography. A deionized water droplet (6 μL) was dropped onto the sample surfaces (20 × 25 × 0.7 mm) that were heated to temperatures ranging from 250°C to the LFP. The modified zirconium alloy surfaces showed complete wetting and well-spread features at room temperature due to strong liquid spreading by the structure. The meniscus of the liquid droplet on the structured surface experienced more vigorous dynamics with intensive nucleate boiling, compared with the clean, bare surface. The cutback phenomenon was observed on the bare surface; however, the structured surfaces showed a water droplet “burst”. We observed that the LFPs were 449°C, 522°C, and 570°C, corresponding to the bare, micro-, and nano-structures, respectively.

Initial spreading dynamics of a liquid droplet: The effects of wettability, liquid properties, and substrate topography

2021 ◽  
Vol 33 (4) ◽  
pp. 042118
Author(s):  
Jiayu Du ◽  
Nikolaos T. Chamakos ◽  
Athanasios G. Papathanasiou ◽  
Qi Min
Keyword(s):  
Liquid Droplet ◽  
Substrate Topography ◽  
Spreading Dynamics

The Effect of Nano-Structured Surfaces on Droplet Impingement Heat Transfer

2011 ◽  
Author(s):  
Gary Rosengarten ◽  
Anggito Tetuko ◽  
Ka Kit Li ◽  
Alex Wu ◽  
Robert Lamb
Keyword(s):  
Heat Transfer ◽  
Surface Properties ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
High Speed ◽  
Liquid Droplet ◽  
Droplet Impingement ◽  
Cooling Effectiveness ◽  
Structured Surfaces ◽  
The Impact

Droplet impingement is a fundamental process for many applications particularly those involving heat transfer. While there has been considerable work over many years on understanding the flow and heat transfer processes, we have only recently been able to fabricate controllable nanostructured surfaces. Surface structure can have a massive impact on the droplet impact process dynamics and the associated convective heat transfer from the liquid droplet to the surface. In this paper we examine the impact dynamics and heat transfer using simultaneous high speed thermal imaging of the liquid from below, and high speed video camera images from the side for different surfaces, ranging from hydrophilic to superhydrophobic. In this way we characterize the heat transfer process as a function of the droplet dynamics and the surface properties. We show that the heat transfer rate is primarily affected by the contact line dynamics and the wetted area. Due to the superhydrophobic roughness scale being relatively small, the interface resistance offered by the trapped air has only a small effect on the heat transfer rate, and only in the inertia dominated region before maximum spreading diameter. Finally we show that the overall cooling effectiveness of as single impinging droplet is very dependent on the surface properties with hydrophilic surfaces offering the highest cooling effectiveness.

TECHNOLOGIES FOR MANUFACTURING NANOSTRUCTURED SURFACES

2020 ◽  
Author(s):  
Андрей Дмитриевич Бухтеев ◽  
Виктория Буянтуевна Бальжиева ◽  
Анна Романовна Тарасова ◽  
Фидан Гасанова ◽  
Светлана Викторовна Агасиева
Keyword(s):  
Plastic Deformation ◽  
Surface Modification ◽  
Severe Plastic Deformation ◽  
Pressing Pressure ◽  
Pressure Treatment ◽  
Structured Surfaces ◽  
Nanostructured Surfaces ◽  
Angular Pressing ◽  
Multilayer Composites ◽  
Compaction Of Powders

В данной статье рассматривается применение и технологии получения наноструктурированных поверхностей. Рассмотрены такие методы как компактирование порошков (изостатическое прессование, метод Гляйтера), интенсивная пластическая деформация (угловое кручение, равноканальное угловое прессование, обработка давлением многослойных композитов) и модификация поверхности (лазерная обработка, ионная бомбардировка). This article discusses the application and technology for obtaining nano-structured surfaces. Methods such as compaction of powders (isostatic pressing, Gleiter method), severe plastic deformation (angular torsion, equal-channel angular pressing, pressure treatment of multilayer composites) and surface modification (laser treatment, ion bombardment) are considered.

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