High Speed SPR Visualization of Frost Propagation Inside a Subcooled Water Droplet

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Chan Ho Jeong ◽  
Seong Hyuk Lee ◽  
Dong Hwan Shin ◽  
Vinaykumar Konduru ◽  
Jeffrey S. Allen ◽  
...  
Keyword(s):  
Water Droplet ◽  
High Speed ◽  
Gold Film ◽  
Liquid Droplet ◽  
Monochromatic Light ◽  
Nucleation Site ◽  
Cover Glass ◽  
Thermo Electric ◽  
Subcooled Liquid ◽  
Central Droplet

A surface plasmon resonance (SPR) imaging microscopy coupled to a high-speed camera is used to visualize the frost propagation inside a subcooled liquid droplet. The SPR experimental setup consists of a 50 nm thick gold-coated cover glass placed on a BK7 dove prism and optically matched using index matching liquid. Collimated monochromatic light of 600 nm wavelength is incident on the gold-glass interface at 71.8°, which corresponds to the SPR minima angle for ice (RI 1.309). Images are captured using Photron APS-RS camera at 1000 fps with a shutter speed of 1 ms. The prism and the gold film are cooled using a thermo-electric cooler (TEC). A water droplet is placed on the gold film and the temperature of the droplet is decreased from room temperature (23.0 ± 1 °C) to below 0 °C. Adjacent to the water droplet, the vapor condensates to form tiny droplets. The tiny condensate droplets would freeze first and the frost propagates through the condensate region. During this period the central droplet is in a subcooled state. The speed of frost propagation through the condensates is slow and takes tens of seconds to cover the gold film with ice. Within a single condensate droplet, however, the frost propagation velocity is expected to be considerably higher. Eventually the frost line reaches the central droplet. There is a delay of few seconds between the frost line reaching the droplet and frost propagation inside the droplet. The point at which frost touches the subcooled droplet acts as a nucleation site for the droplet and the frost propagates in the droplet at high speed. The average velocities of frost propagations in the subcooled liquid droplet were calculated to be 5.2 ± 0.3 cm/s and 7.4 ± 0.5 cm/s, when the gold film temperature was -5.0 ± 1 °C and -7.8 ± 1 °C respectively.

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.

High-Speed Surface Plasmon Resonance (SPR) Reflectance Imaging of Drop Coalescence during Condensation and Evaporation

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Vinaykumar Konduru ◽  
Dong Hwan Shin ◽  
Jeffrey S. Allen ◽  
Chang Kyoung Choi ◽  
Seong Hyuk Lee ◽  
...  
Keyword(s):  
Refractive Index ◽  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
High Speed ◽  
Gold Film ◽  
Resonance Condition ◽  
Monochromatic Light ◽  
Test Medium ◽  
Drop Coalescence

Drop condensation and coalescence is visualized using high-speed Surface Plasmon Resonance (SPR) reflectance microscopy. SPR microscopy is a label-free technique that can characterize thin films (less than 1µm) by detecting the changes in the refractive index of the test medium. The sensing surface is a 50 nm thick gold film on a 2.5 nm thick Ti layer is deposited on a borosilicate substrate. P-polarized monochromatic light (632 nm) is incident on the gold film in a total internal reflection mode. Free electrons in the gold film are excited by the incident light when a resonance condition is met. The result is a decrease in the reflected intensity. Resonance depends upon wavelength, incident angle, and refractive index of prism and test medium. To induce condensation, a water bridge is created between the SPR gold film and an ITO coated glass slide. When the ITO coated slide is heated water evaporates from the bridge and condenses on the gold film. The sequence of images on the process of droplet deposition and drop coalescence are captured at 1500 frames per second. Experiments were conducted at an SPR angle of 44o, which is slightly above the minimum intensity angle for air at 43.8o. Therefore, the brightest and darkest regions correspond to the areas on the gold film covered with bulk water and a very thin film of water, respectively. The thickness of the film is proportional to the intensity of reflected light.

Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Hirotoshi Sasaki ◽  
Yuka Iga
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Erosion Rate ◽  
Liquid Droplet ◽  
Material Surface ◽  
Liquid Droplets ◽  
Fluid Machinery ◽  
Droplet Impingement ◽  
Surface Liquid ◽  
Droplet Impingement Erosion

This study explains why the deep erosion pits are formed in liquid droplet impingement erosion even though the droplets uniformly impinge on the entire material surface. Liquid droplet impingement erosion occurs in fluid machinery on which droplets impinge at high speed. In the process of erosion, the material surface becomes completely roughened by erosion pits. In addition, most material surface is not completely smooth and has some degree of initial roughness from manufacturing and processing and so on. In this study, to consider the influence of the roughness on the material surface under droplet impingement, a numerical analysis of droplets impinging on the material surface with a single wedge and a single bump was conducted with changing offsets between the droplet impingement centers and the roughness centers on each a wedge bottom and a bump top. As results, two mechanisms are predicted from the present numerical results: the erosion rate accelerates and transitions from the incubation stage to the acceleration stage once roughness occurs on the material surface; the other is that deep erosion pits are formed even in the case of liquid droplets impinging uniformly on the entire material surface.

Dynamics of thin precursor film in wetting of nanopatterned surfaces

2021 ◽  
Vol 118 (38) ◽  
pp. e2108074118
Author(s):  
Utkarsh Anand ◽  
Tanmay Ghosh ◽  
Zainul Aabdin ◽  
Siddardha Koneti ◽  
XiuMei Xu ◽  
...  
Keyword(s):  
High Speed ◽  
Liquid Droplet ◽  
Water Film ◽  
Precursor Film ◽  
Intermediate Step ◽  
Dense Array ◽  
Flat Surfaces ◽  
Transmission Electron ◽  
Phase Transmission ◽  
Two Stages

The spreading of a liquid droplet on flat surfaces is a well-understood phenomenon, but little is known about how liquids spread on a rough surface. When the surface roughness is of the nanoscopic length scale, the capillary forces dominate and the liquid droplet spreads by wetting the nanoscale textures that act as capillaries. Here, using a combination of advanced nanofabrication and liquid-phase transmission electron microscopy, we image the wetting of a surface patterned with a dense array of nanopillars of varying heights. Our real-time, high-speed observations reveal that water wets the surface in two stages: 1) an ultrathin precursor water film forms on the surface, and then 2) the capillary action by nanopillars pulls the water, increasing the overall thickness of water film. These direct nanoscale observations capture the previously elusive precursor film, which is a critical intermediate step in wetting of rough surfaces.

Sliding Dynamics of a Water Droplet On Silicon Oil Film Surface

2021 ◽  
Author(s):  
Bekir Sami Yilbas ◽  
Anwaruddin Siddiqui Mohammed ◽  
Abba Abdulhamid Abubakar ◽  
Saeed Bahatab ◽  
Hussain Al-Qahtani ◽  
...  
Keyword(s):  
Water Droplet ◽  
High Speed ◽  
Film Surface ◽  
Maximum Velocity ◽  
Optical Transmittance ◽  
Gravitational Energy ◽  
Droplet Motion ◽  
Droplet Dynamics ◽  
Oil Film ◽  
Silicon Oil

Abstract A sliding droplet over the silicon oil film is examined and the dynamics of droplet motion are explored. The solution crystallized wafer surfaces are silicon oil impregnated and the uniform thickness oil film is realized. A recording facility operating at high-speed and the tracker program are used to monitor and evaluate the droplet dynamics during droplet sliding. The sliding behavior and flow generated in the droplet fluid are predicted by adopting the experimental terms. Findings revealed that the crystallized surface possesses the texture composing of spherules and fibrils, which give rise to 132o ± 4o contact angle and 38o ± 4o hysteresis. Oil impregnation on the crystalized surface improves the optical transmittance by three times for 250 nm to 500 nm wavelength range and almost 1.5 times after 500 nm to 850 nm wavelengths of the optical spectrum. The oil rim and ridges are developed in sliding water droplet vicinity while influencing droplet motion; however, this influence is estimated as almost 12% of droplet gravitational energy change during sliding. A circulatory flow is developed inside the droplet fluid and the maximum velocity in the droplet fluid changes as the droplet location changes on the oil surface during its sliding.

scholarly journals CNN-based visual analysis to study local boiling characteristics

2021 ◽  
Vol 2119 (1) ◽  
pp. 012068
Author(s):  
A N Chernyavskiy ◽  
I P Malakhov
Keyword(s):  
Network Architecture ◽  
High Speed ◽  
Visual Analysis ◽  
Nucleation Site ◽  
High Speed Video ◽  
Site Density ◽  
Segmentation Approach ◽  
Nucleation Site Density ◽  
Instance Segmentation

Abstract Visual analysis allows an estimate of different local boiling characteristics including bubble growth rate, departure diameters and frequencies of nucleation, nucleation site density and evolution of bubbles and dry spots in time. At the same time, visual determination of the presented characteristics in case of big amounts of data requires the development of the appropriate software which will allow not only determination of bubble location, but also an estimate of their sizes based on high-speed video. The presented problem can be solved by using the instance segmentation approach based on a convolutional neural network. In the presented work Mask R-CNN network architecture was used for estimation of the local boiling characteristics.

scholarly journals A water droplet-cleaning of a dusty hydrophobic surface: influence of dust layer thickness on droplet dynamics

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ghassan Hassan ◽  
Bekir S. Yilbas ◽  
Saeed Bahatab ◽  
Abdullah Al-Sharafi ◽  
Hussain Al-Qahtani
Keyword(s):  
Layer Thickness ◽  
Inclination Angle ◽  
Water Droplet ◽  
High Speed ◽  
Small Volume ◽  
Transition Period ◽  
Imaging System ◽  
Hydrophobic Surface ◽  
Dust Layer ◽  
Surface Inclination

Abstract Water droplet cleaning of a dusty hydrophobic surface is examined. Environmental dust are used in the experiments and cloaking velocity of a dust layer by a droplet fluid is measured and hemi-wicking conditions for the dust layer are analyzed adopting the pores media wick structure approach. A droplet motion on dusty and inclined hydrophobic surface is analyzed using a high speed digital imaging system. Influences of dust layer thickness, droplet volume, and surface inclination angle on the mechanisms of dust removal by a rolling droplet are evaluated. The findings revealed that dust cloaking velocity decreases exponentially with time. The droplet fluid can cloak the dust layer during its transition on the dusty surface. The transition period of droplet wetted length on the dusty surface remains longer than the cloaking time of the dust layer by the droplet fluid. Translational velocity of rolling droplet is affected by the dust layer thickness, which becomes apparent for small volume droplets. Small volume droplet (20 µL) terminates on the thick dust layer (150 µm) at low surface inclination angle (1°). The quantity of dust picked up by the rolling droplet increases as the surface inclination angle increases. The amount of dust residues remaining on the rolling droplet path is relatively larger for the thick dust layer (150 µm) as compared to its counterpart of thin dust layer (50 µm).

QWIPs DESIGNED FOR HIGH ABSORPTION AND HIGH OPERATING TEMPERATURE

2002 ◽  
Vol 12 (03) ◽  
pp. 803-819 ◽  
Author(s):  
H. C. Liu ◽  
R. Dudek ◽  
A. Shen ◽  
E. Dupont ◽  
C.-Y. Song ◽  
...  
Keyword(s):  
Quantum Wells ◽  
High Speed ◽  
Room Temperature ◽  
Operating Temperature ◽  
Absorption Efficiency ◽  
Thermo Electric ◽  
Doping Density ◽  
Detection Of Weak Signals ◽  
High Absorption ◽  
Room Temperature Operation

For the majority of applications involving detection of weak signals or thermal imaging, the quantum well infrared photodetector (QWIP) is designed to have the highest possible detectivity and operating temperature. The device parameters, such as the doping density, are chosen accordingly. In a different direction, the intrinsic short carrier lifetime (~ 5 ps) makes QWIPs well suited for high speed and high frequency applications. In such cases, since lasers are normally used, a high dark current can be tolerated. The most important parameter is then the absorption efficiency. For system simplicity and potential wide use, room temperature or near room temperature (reachable by thermo-electric cooling) operations are desirable. This paper discusses the QWIP design for high absorption and elevated temperature operation, and present a systematic experimental study on a set of GaAs/AlGaAs QWIPs with different doping densities. High absorption (~ 100%) and up to room temperature operation are achieved in devices having high doping densities and 100 quantum wells.

Microbubble Formation in Collapsing Process of a Single Vapor Bubble Injected in Subcooled Pool

2009 ◽  
Author(s):  
Ichiro Ueno ◽  
Yasusuke Hattori
Keyword(s):  
Heat Flux ◽  
Vapor Bubble ◽  
High Speed ◽  
Narrow Range ◽  
Heated Surface ◽  
Lighting System ◽  
Vapor Bubbles ◽  
Bubble Behavior ◽  
Subcooled Liquid ◽  
Boiling Process

‘Microbubble emission boiling,’ known as MEB, is a phenomenon that emerges in a narrow range of subcooled condition with a higher heat flux than critical heat flux (CHF) accompanying with microbubble emission from the heated surface. The authors focus on the condensing process of vapor bubbles in order to comprehend the mechanism of the microbubble formation and emitting processes. In order to simplify a surely complex boiling process, the authors try to extract an interaction between the vapor bubble and the subcooled bulk in a boiling phenomenon, that is, growing and collapsing processes of a vapor bubble ejected to subcooled liquid bath. Vapor bubble is produced by vapor generate system, and ejected to a bulk of saturated distilled water at a designated degree of subcooling. The degree of subcooling is varied from 0 to 50 K. The growing/collapsing of vapor bubble behavior is detected by employing a high-speed camera at frame rates up to 50,000 fps with a back-lighting system. In the present study, the process of microbubble emission as well as the process of the irrupting vapor bubbles to the subcooled bulk is compared to that in a MEB on a thin wire.

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