Download or read book Experimental Investigation of Droplet Impact Dynamics on Solid Surfaces written by Kalpak Prakash Gatne and published by . This book was released on 2006 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this thesis. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four pure liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. To understand the influence of drop size, experiments were performed in which the drop size was varied for the same fluid. Also, the effect of substrate material was studied by comparing the impact on two different substrates: glass (hydrophilic) and PTFE or Teflon (hydrophobic). The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. Experiments were performed to study the influence of addition of surface active agents or surfactants in aqueous solution on the droplet impact phenomenon. Three surfactants were used with varying diffusion rates: SDS (anionic), CTAB (cationic) and Triton x 100 (non ionic). The spreading and recoil of the drops of surfactant solutions is studied at concentrations of half the critical micelle concentration (CMC) and twice CMC. To underscore the dynamic effects, comparative experiments for the three surfactants were performed so that all the solutions had the same value of equilibrium surface tension. The role played by impact velocity in the collision of surfactant laden drops was studied by comparing the results for two different impact velocities. The influence of surfactant concentration was studied by performing experiments varying the surfactant concentrations. The results show that changes in liquid viscosity, surface tension, and surfactant concentration significantly affect the spreading and recoil behavior. In the case of pure liquids, for a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re 1/5when liquid viscosity is high and viscous effects govern the spreading behavior. The drop size had no binding when the Weber number was maintained constant and the Reynolds numbers were comparable. The nature of the substrate plays a very important role. Impact on hydrophobic substrates can result in dramatic recoils and rebound. For aqueous solutions with surface active agents, it was observed that higher diffusion rate surfactants result in higher spreading factors and weaker oscillations. The spreading and recoil behavior can be correlated to the dynamic surface tension response of the surfactant solutions. With increase in impact velocity, the gain in spreading factor over a pure water drop decreases. Also, lowering of the surfactant concentration results in lower spreading factor and stronger recoil - a behavior closer to that of pure water.

Download or read book Experimental Investigation of Liquid Droplet Impact on a Smooth Quartz Surface written by Brett Frederick Bathel and published by . This book was released on 2007 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Drop Surface Interactions written by Martin Rein and published by Springer Science & Business Media. This book was released on 2002-10-30 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of fluid mechanical, thermal and physico-chemical aspects of drop-surface interactions. Basic physical mechanisms pertaining to free-surface flow phenomena characteristic of drop impact on solid and liquid surfaces are explained emphasizing the importance of scaling. Moreover, physico-chemical fundamentals relating to a forced spreading of complex solutions, analytical tools for calculating compressibility effects, and heat transfer and phase change phenomena occurring during solidification and evaporation processes, respectively, are introduced in detail. Finally, numerical approaches particularly suited for modeling drop-surface interactions are consisely surveyed with a particular emphasis on boundary integral methods and Navier-Stokes algorithms (volume of fluid, level set and front tracking algorithms). The book is closed by contributions to a workshop on Drop-Surface Interactions held at the International Centre of Mechanical Sciences.

Download or read book Impact Velocity and Surface Temperature Effects on the Collision of a Molten Tin Droplet on a Solid Surface written by Shiraz Dean Aziz and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation was performed on the splashing and freezing of molten tin droplets on a stainless steel surface. The diameter of the droplets was 2.7 mm, and the impact velocity ranged from 1.0 m/s to 4.0 m/s. The substrate temperature was varied from 25$\sp\circ$C to 240$\sp\circ$C. Droplet impact was photographed using a 35 mm camera; both the splat diameter and liquid-solid contact angle were measured from these photographs. The substrate temperature under the impacting droplet was measured using a fast response thermocouple. The heat transfer coefficient during the first 0.5 ms of impact was obtained by matching measured surface temperature variation with an analytical solution. A simple energy conservation model was used to predict the maximum spreading of the droplet during impact. The predictions agreed well with experimental values. Instabilities were observed on the periphery of the droplet, which led to the formation of a finger pattern at velocities above 1.0 m/s. A model based on the Rayleigh-Taylor instability was used to predict the number of fingers around the periphery of the droplet.

Download or read book Dynamics of Droplets written by Arnold Frohn and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book deals with the dynamical behaviour of single droplets and regular droplet systems. It has been written mainly for experimental researchers. After a short description of the theoretical background, the different experimental facilities and methods necessary for the investigation of single droplets are described in detail. A summary of important applications is included.

Download or read book Droplet and Spray Transport Paradigms and Applications written by Saptarshi Basu and published by Springer. This book was released on 2017-12-12 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on droplets and sprays and their applications. It discusses how droplet level transport is central to a multitude of applications and how droplet level manipulation and control can enhance the efficiency and design of multiphase systems. Droplets and sprays are ubiquitous in a variety of multiphase and multiscale applications in surface patterning, oil recovery, combustion, atomization, spray drying, thermal barrier coating, renewable energy, and electronic cooling, to name but a few. This book provides two levels of details pertaining to such applications. Each chapter delves into a specific application and provides not only an overview but also detailed physical insights into the application mechanism from the point of view of droplets and sprays. All chapters provide a mix of cutting-edge applications, new diagnostic techniques and modern computational methodologies, as well as the fundamental physical mechanism involved in each application. Taken together, the chapters provide a translational perspective on these applications, from basic transport processes to optimization, and from design to implementation using droplets or sprays as fundamental building blocks. Given its breadth of coverage, the book will be of interest to students, researchers, and industry professionals alike.

Download or read book Droplet Impact Dynamics and Related Heat Transfer Phenomena written by Jie Liu and published by . This book was released on 2008 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Investigation of Water Droplet Impact and Icing on Hydrophobic Surfaces with Varying Wettabilities written by Yuntao Pan and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ice formation and accumulation can lead to operational failure and risks for structures such as power transmission lines, aircrafts, offshore platforms, marine vessels and wind turbines. Liquid repellent surfaces could reduce ice accretion and improve asset integrity and safety in harsh environments. there are significant needs to probe how surface wettability affects the droplet impact, ice formation and ice accretion processes. This study presents experimental results of water droplet impact, droplet dynamics, and icing delay time on flat and inclined stainless-steel surfaces with varying wettabilities. Several different designs of the micro-structure of the hydrophobic surfaces are considered. The commercial hydrophobic coating from Aculon is also used to improve liquid repellency and reduce ice accumulation. It was found that the impact speed and surface wettability are significant factors to the droplet oscillation and the total icing time. The droplet oscillation time is significantly longer on a hydrophobic surface than on a hydrophilic one. Lower surface wettability also significantly increases the droplet total icing time. The droplet total icing time decreases with lower droplet temperature, larger droplet impact velocity, and smaller droplet diameter. The droplet shows a gliding phase on an inclined surface. The total icing time decreases on the inclined surface since the contact area increases due to the gliding process. for typical droplet icing process, the ice formation initiates at the solid-liquid interface and then propagates from bottom to top through the liquid-gas interface. The droplet bounces off from the angled superhydrophobic surface made by electrodeposition at room temperature.

Download or read book Direct Numerical Simulations of Gas Liquid Multiphase Flows written by Grétar Tryggvason and published by Cambridge University Press. This book was released on 2011-03-10 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurately predicting the behaviour of multiphase flows is a problem of immense industrial and scientific interest. Modern computers can now study the dynamics in great detail and these simulations yield unprecedented insight. This book provides a comprehensive introduction to direct numerical simulations of multiphase flows for researchers and graduate students. After a brief overview of the context and history the authors review the governing equations. A particular emphasis is placed on the 'one-fluid' formulation where a single set of equations is used to describe the entire flow field and interface terms are included as singularity distributions. Several applications are discussed, showing how direct numerical simulations have helped researchers advance both our understanding and our ability to make predictions. The final chapter gives an overview of recent studies of flows with relatively complex physics, such as mass transfer and chemical reactions, solidification and boiling, and includes extensive references to current work.

Download or read book An Experimental Investigation of Drop Impact Phenomena with Complex Fluids on Heated and Soft Surfaces written by S. Chen and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 12th International Symposium on High Temperature Metallurgical Processing written by Zhiwei Peng and published by Springer Nature. This book was released on 2022-02-04 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection includes the analysis, development, and operation of high-temperature processes that involve the extraction and processing of material resources, production, and treatment of metals, alloys, and ceramic materials. Contributions describe innovative methods for achieving property enhancement, impurity segregation and removal, byproduct recovery, waste minimization, energy efficiency, and utilization of complex ores. Also included are various technical, economic, and environmental issues associated with commercial-scale high-temperature processing methods.

Download or read book Collision Phenomena in Liquids and Solids written by Alexander L. Yarin and published by Cambridge University Press. This book was released on 2017-06-15 with total page 629 pages. Available in PDF, EPUB and Kindle. Book excerpt: A unique and in-depth discussion uncovering the unifying features of collision phenomena in liquids and solids, along with applications.

Download or read book Droplet Dynamics Under Extreme Ambient Conditions written by Kathrin Schulte and published by Springer Nature. This book was released on 2022 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book presents the main results of the Collaborative Research Center SFB-TRR 75, which spanned the period from 2010 to 2022. Scientists from a variety of disciplines, ranging from thermodynamics, fluid mechanics, and electrical engineering to chemistry, mathematics, computer science, and visualization, worked together toward the overarching goal of SFB-TRR 75, to gain a deep physical understanding of fundamental droplet processes, especially those that occur under extreme ambient conditions. These are, for example, near critical thermodynamic conditions, processes at very low temperatures, under the influence of strong electric fields, or in situations with extreme gradients of boundary conditions. The fundamental understanding is a prerequisite for the prediction and optimisation of engineering systems with droplets and sprays, as well as for the prediction of droplet-related phenomena in nature. The book includes results from experimental investigations as well as new analytical and numerical descriptions on different spatial and temporal scales. The contents of the book have been organised according to methodological fundamentals, phenomena associated with free single drops, drop clusters and sprays, and drop and spray phenomena involving wall interactions.

Download or read book Drops and Bubbles in Contact with Solid Surfaces written by Michele Ferrari and published by CRC Press. This book was released on 2012-10-17 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: The third volume in a series dedicated to colloids and interfaces, Drops and Bubbles in Contact with Solid Surfaces presents an up-to-date overview of the fundamentals and applications of drops and bubbles and their interaction with solid surfaces. The chapters cover the theoretical and experimental aspects of wetting and wettability, liquid–solid interfacial properties, and spreading dynamics on different surfaces, including a special section on polymers. The book examines issues related to interpretation of contact angle from nano to macro systems. Expert contributors discuss interesting peculiarities, such as the phenomena of super-spreading and super-hydrophobicity. They discuss specific solid surfaces—for example, reactions and wetting of liquid metals at high temperatures—and the interaction between nano-bubbles at solid surface and nano-particles at liquid interfaces. The book also includes a chapter on electro-wetting. Given the range of topics covered in this volume, the state-of-art content is useful to readers looking for an introductory overview as well as those looking for in-depth exploration of material related to the interaction of fluids with solid surfaces. It is a valuable contribution to the field of characterization of solid surfaces and can be used as a working tool or to stimulate further study for researchers and students.

Download or read book EXPERIMENTAL INVESTIGATION OF IMPINGED DROPLET DYNAMICS written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : The fuel spray wall interaction phenomenon plays an essential role in determining the emissions and performance of an internal combustion engine. The investigation of single droplet wall interaction is crucial to understanding of a spray wall impingement process. This report is a compilation of the experimental work done to understand the droplet impingement characteristics, through optical diagnostics and temperature measurement. Different fuels and different surface under ambient and elevated temperature conditions are used for these tests, with two objectives: Development of a common depositionsplashing criteria; and Understanding droplet post impingement dynamics variation with factors like: Weber number (ratio of inertia and surface tension forces), and with temperature. The droplet post impinging characteristics include spread factor, height ratio, contact line velocity and dynamic contact angle. The effect of Weber no on droplet impingement characteristics is investigated using water and diesel. The effect of temperature is divided into two subsections: Isothermal (cold wall-cold droplet and hot wall-hot droplet) and non-isothermal conditions (hot wall-cold droplet and hot droplet and cold wall), to understand the influence of both variation in thermophysical properties and heat transfer between droplet and surface. Using the experimental results, a comprehensive review of splashing criteria is done, along with a proposed new correlation for same and concept of splashing probability is introduced. The observation presented for variation in post-impingement characteristics with the mentioned factors are useful for future development of numerical codes.

Download or read book Capillarity and Wetting Phenomena written by Pierre-Gilles de Gennes and published by Springer Science & Business Media. This book was released on 2013-03-20 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of capillarity is in the midst of a veritable explosion. What is offered here is not a comprehensive review of the latest research but rather a compendium of principles designed for the undergraduate student and for readers interested in the physics underlying these phenomena.

Download or read book Droplet Impact and Solidification on Solid Surfaces in the Presence of Stagnation Air Flow written by Morteza Mohammadi and published by . This book was released on 2016 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the fundamentals of ice accretion on surfaces can help in proposing solutions to reduce or prevent ice accumulation on aircraft components and power lines. The main way in which ice forms on a surface is the solidification of supercooled droplets upon impacting on the surface. On an aircraft wing, ice accumulation can easily change the flow pattern, which could result in an increase in drag force. This research investigates the use of superhydrophobic coatings (surfaces with contact angles larger than 150) to counteract icing (anti-icing) as a result of their extremely low surface energy. The main goal of this study is to assess the performance of superhydrophobic surfaces in the presence of stagnation flow to mimic flight conditions (e.g. droplet impinging on the leading edge of an aircraft’s wing). A wide range of droplet impact velocities and stagnation flows in splashing and non-splashing regimes (at high and low Weber numbers) were carried out on surfaces with various wettabilities. The results were analyzed in order to highlight the advantages of using superhydrophobic coatings. Free stream air velocity were varied from 0 to 10 m/s with a temperature which was controlled from room temperature at 20 oC down to -30 oC. It was observed that while the presence of stagnation flow on hydrophilic (i.e. aluminum substrate) results in thin film formation for droplets with Weber numbers more than 220 upon impact in room temperature condition, instantaneous freezing at the maximum spreading diameter was observed in low temperature condition where air and substrate temperature was below the -20 oC. Same phenomenon was observed for hydrophobic substrate at aforementioned temperature. On the other hand, striking phenomenon was observed for superhydrophobic surface when stagnation air flow is present. Although it was expected droplet contact time to be increased by imposing stagnation air flow on an impacting droplet it was reduced as a function of droplet Weber number. This was referred to the presence of full slip condition rather than partial one where the spreading droplet moves on thin layer of air. Consequently, it promotes droplet ligament detachment through Kelvin-Helmholtz instability mechanism. While in low temperature condition above temperature of heterogeneous ice nucleation (i.e. -24 oC)1 supercooled water droplet contact time is reduced up to 30% to that of still air cases, droplet solidified diameter was increased up to 2 folds for air velocity up to 10 m/s compare to the still air condition at temperatures as low as -30 oC. These results were compared with a new predictive model of droplet impact behavior on the superhydrophobic substrate. New universal predictive model of droplet impact dynamics on the superhydrophobic surface was developed based on the concept of mass-spring model2 which was validated against experimental results. In the new model, viscosity effect was considered through adding a dashpot term in mass-spring model. In addition, the effect of stagnation flow was also integrated to the model through classical Homann flow approach.3 For non-isothermal condition, the effect of phase change (i.e. solidification) on droplet wetting dynamics was coupled to the model through classical nucleation theory. The universal model was compared against experimental results in room and low temperature conditions (i.e. supercooled condition) for model’s validation.