Dynamic Contact Angle of Modified Biopolymer Droplet on Urea Surface: Temperature Effects

2013 ◽  
Vol 594-595 ◽  
pp. 566-570 ◽  
Author(s):  
Yon Norasyikin Samsudin ◽  
Ku Zilati Ku Shaari ◽  
Zakaria Man ◽  
Suriati Sufian
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Dynamic Contact Angle ◽  
Ccd Camera ◽  
Dynamic Contact ◽  
Droplet Impact ◽  
Coating Material ◽  
Coating Process ◽  
Fluidised Bed ◽  
Impact Behaviour

The droplet impact behaviour provides the particle coating characterization during the coating process of controlled release fertiliser. To have a good coating uniformity around the urea granules, it is necessary to enhance the wettabitily properties between the coating material and urea surface. The biopolymer material is preferred as the coating material because this polymer may degrade and will not cause any environmental impact to the environment. Various compositions of starch/urea /borate/lignin were prepared and evaluated for the wettability properties. The wettability characteristic measured is the dynamic contact angle. The high speed Charged-Couple Device (CCD) camera was used to capture the images of this droplet impact behaviour. Temperature plays an important factor during wetting stage because the coating material must be completely dried in continuous coating process in fluidised bed. From this analysis, it indicates that a composition of starch/urea/ borate (50/15/2.5) with 10% lignin has the best wettability characteristic and thus suitable to be used as a coating material. The ideal temperature for the coating process is 60°C.

Dynamics of Droplet Motion Induced by Electrowetting

2016 ◽  
Author(s):  
Yi Lu ◽  
Aritra Sur ◽  
Dong Liu ◽  
Carmen Pascente ◽  
Paul Ruchhoeft
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Numerical Models ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
High Speed Photography ◽  
Droplet Dynamics ◽  
Droplet Shape ◽  
Moving Contact Line ◽  
Moving Contact

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.

scholarly journals The Effect of Surface Roughness on the Contact Line and Splashing Dynamics of Impacting Droplets

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Miguel A. Quetzeri-Santiago ◽  
Alfonso A. Castrejón-Pita ◽  
J. Rafael Castrejón-Pita
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
High Speed ◽  
Dynamic Contact Angle ◽  
Past Research ◽  
Dynamic Contact ◽  
Substrate Roughness ◽  
High Speed Imaging ◽  
Mean Width ◽  
Fluid Properties

Abstract Whether a droplet splashes upon impact onto a solid is known to depend not only on the fluid properties and its speed, but also on the substrate characteristics. Past research has shown that splashing is heavily influenced by the substrate roughness. Indeed, in this manuscript, we demonstrate that splashing is ruled by the surface roughness, the splashing ratio, and the dynamic contact angle. Experiments consist of water and ethanol droplets impacting onto solid substrates with varying degrees of roughness. High speed imaging is used to extract the dynamic contact angle as a function of the spreading speed for these impacting droplets. During the spreading phase, the dynamic contact angle achieves an asymptotic maximum value, which depends on the substrate roughness and the liquid properties. We found that this maximum dynamic contact angle, together with the liquid properties, the ratio of the peak to peak roughness and the surface feature mean width, determines the splashing to no-splashing threshold. In addition, these parameters consistently differentiate the splashing behaviour of impacts onto smooth hydrophilic, hydrophobic and superhydrophobic surfaces.

A Numerical Investigation of the Free Surface Flow During Optical Fiber Coating Process

2001 ◽  
Author(s):  
C. S. L. Liu ◽  
S. H.-K. Lee
Keyword(s):  
Contact Angle ◽  
Free Surface ◽  
Optical Fiber ◽  
Dynamic Contact Angle ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Coating Process ◽  
Coating Quality ◽  
Fiber Coating ◽  
Drawing Speed

Abstract Optical fiber has increasingly played a crucial role in the information transmission area nowadays. The elevated demand makes it necessary to manufacture high quality light-guide fibers that have proper mechanical properties to endure the stresses induced during installations and operations. Optical fiber coating process provides a protection layer to shield the fiber from surface abrasion and also to increase the fiber’s tensile strength. However, there are problems encountered during this process which reduce the coating quality. One of the major problems is air entrainment, which may lead to eccentrical or incomplete coating. Apparently, it is of great interest to study this problem to improve the coating quality. Many experimental studies have been performed on the dynamic contact angle, air entrainment velocity and their correlation with various parameters, such as the viscosity and the surface tension of coating materials, fiber drawing speed, etc. Nevertheless, how the coating flow affects the upper meniscus (directly related with dynamic contact angle and air entrainment) has not been intensively studied. Understanding of the effects is essential to improve the coating quality. To fulfill this requirement, the present work focused on investigating the relation of upper meniscus and fiber drawing speed. This is just the first part of the serial study on the optical fiber coating process. Firstly, a numerical code was developed with finite volume formulation. The results showed that the code had the capacity to deal with this free surface fluid flow problem. The simulated free surface shape was validated with experimental data available. The trend of the upper meniscus shape and dynamic contact angle developments at high drawing velocity was simulated. The results showed, as expected, that the dynamic contact angle would approach 180° with the increase of the fiber-drawing speed.

scholarly journals Hydrodynamic Study of an Oscillating Meniscus in a Square Mini-Channel

2009 ◽  
Author(s):  
Yajuvendra Singh Shekhawat ◽  
Sameer Khandekar ◽  
Pradipta Kumar Panigrahi
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Capillary Tube ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Glass Capillary ◽  
Two Fluids ◽  
Silicon Oil ◽  
Static Contact ◽  
Micro Systems

Miniaturized fluidic systems like MEMS may involve single-phase or multi-phase flows with oscillations/ pulsations. Understanding the hydrodynamics of such flows can help in manipulating the performance parameters and improving the efficiency of micro-systems. This work focuses on hydrodynamics of a sinusoidally oscillating meniscus in a square mini-channel. The interfacial contact line behavior of a single oscillating meniscus formed between liquid slug and air, inside the square capillary tube, has been explored. An eccentric cam follower system has been fabricated to provide sinusoidal oscillations of fluid in the square glass capillary having hydraulic diameter of 2.0 mm. Experiments are conducted with two fluids, water and silicon oil. Dynamic contact angle measurements are carried out for water at two oscillating frequencies, 0.25 Hz and 0.50 Hz using high speed videography. It is seen that an increase in the oscillating frequency increases the difference in the advancing angle and receding angle of the meniscus, with the static contact angle of water on glass surface around 21°. For silicon oil the experiments have been performed at eight different frequencies in the range of 0.20 Hz and 1.00 Hz. It is seen that the meniscus is pinned at the extreme end of the stroke, unlike that in the case of water, and there is a film of silicon oil during oscillations. The thickness of the film formed increases with increase in oscillating frequency. There is considerable difference in the hydrodynamics of silicon oil and water.

Machine Vision Based Measurement of Dynamic Contact Angle in Microchannel Flows

2008 ◽  
Author(s):  
Valtteri Heiskanen ◽  
Pasi Kallio ◽  
Kalle Marjanen
Keyword(s):  
Contact Angle ◽  
Machine Vision ◽  
Dynamic Contact Angle ◽  
Ccd Camera ◽  
Dynamic Contact ◽  
Image Processing Algorithm ◽  
Flowing Liquid ◽  
Liquid Plug ◽  
Custom Made ◽  
Flow Variables

When characterizing flows in miniaturized channels, determination of the dynamic contact angle is important. By measuring the dynamic contact angle, the flow properties of the flowing liquid and the effect of material properties on the flow can be characterized. A machine vision based system to measure the contact angle of a front or rear meniscus of a moving liquid plug is described in this paper. In this research, transparent MABS-based flow channel structures, sealed with adhesive tapes are used. The transparency of the channels enables image based monitoring and measurements of flow variables, including the dynamic contact angle. It is shown that the dynamic angle can be measured from a liquid flow in a channel using the image based measurement system. The image processing algorithm has been developed in a MATLAB environment. Imaging is done using a CCD camera (Firewire connection) and illumination is created using a custom made ring light.

619 Effect of Dynamic Contact Angle on Mercury Droplet Impact

2010 ◽  
Vol 2010.18 (0) ◽  
pp. _619-1_-_619-3_
Author(s):  
Takashi NAOE ◽  
Masatoshi FUTAKAWA ◽  
Richard KENNY ◽  
Masato OTSUKI
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Droplet Impact

Single Droplet Impingment: Effect of Nanoparticles

2008 ◽  
Author(s):  
Jian Shen ◽  
James Liburdy ◽  
Deborah Pence ◽  
Vinod Narayanan
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Early Stage ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Droplet Surface ◽  
Droplet Generator ◽  
Single Droplet ◽  
Spreading Dynamics ◽  
Spreading Rates

This study focuses on the dynamics of water and nanofluids droplet surface impingement. Droplets are generated by a piezoelectric driven droplet generator. A high-speed-high-resolution camera is used to record droplets impacting on a smooth heated silicon surface. Droplet impact velocity, spreading diameter, spreading height and dynamic contact angle are measured by image processing. Results of water and nanofluids are compared to determine effects of nanoparticles on spreading dynamics. It is concluded that the nanofluids result in larger spreading rates, larger spreading diameters and an increase in early stage dynamic contact angle.

The Effects of Asymmetric Micro Ratchets on Dynamic Contact Angle and Pool Boiling Performance

2012 ◽  
Author(s):  
Lance Austin Brumfield ◽  
Sunggook Park
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Pool Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Equilibrium Contact Angle ◽  
Droplet Impingement ◽  
Receding Contact ◽  
Receding Contact Angle

The dynamic advancing and receding contact angles of 5μl water droplets were experimentally measured via the droplet impingement technique on a polished brass surface, one brass symmetric micro ratchet, and five brass asymmetric micro ratchet samples of varying dimensions. Droplets were released from varying heights (Weber number) and the impacts studied via high speed camera. Equilibrium advancing and receding contact angles were measured by placing a water droplet on the surfaces and tilting it. Contact angle values were then compared to an existing pool boiling model which incorporates the dynamic receding contact angle, surface roughness ratio, and equilibrium contact angle.

Visualization of Dynamic Contact Angle

2013 ◽  
Author(s):  
Brandon S. Field
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
High Speed ◽  
Solid Phase ◽  
Capillary Rise ◽  
Dynamic Contact Angle ◽  
Fluid Phase ◽  
Dynamic Contact ◽  
Force Balance ◽  
Receding Contact

Capillary rise of air-water-solid systems have been recorded with high-speed video. Glass and metal have been used as the solid phase, and the dynamic shape of the meniscus and contact angle have been characterized. The advancing and receding contact angle is of interest in computational simulations of boiling flow, and the present visualizations attempt to quantify the dynamic aspects of contact line motion. The centroid of the capillary meniscus has been tracked in order to determine the force at the contact line based on a force balance of the elevated fluid phase. The solid phase is raised and lowered in the fluid at different rates to observe advancing and receding contact lines.

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