Download or read book Splashing and Breakup of Droplets Impacting on a Solid Surface written by Rajeev Dhiman and published by . This book was released on 2009 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two new mechanisms of droplet splashing and breakup during impact have been identified and analyzed. One is the internal rupture of spreading droplet film through formation of holes, and the other is the splashing of droplet due to its freezing during spreading. The mechanism of film rupture was investigated by two different methods. In the first method, circular water films were produced by directing a 1 mm diameter water jet onto a flat, horizontal plate for 10 ms. In the second method, films were produced by making 0.6 mm water droplets impact a solid surface mounted on the rim of a rotating flywheel. Substrate wettability was varied over a wide range, including superhydrophobic. In both cases, the tendency to film rupture first increased and then decreased with contact angle. A thermodynamic stability analysis predicted this behavior by showing that films would be stable at very small or very large contact angle, but unstable in between. Film rupture was also found to be promoted by increasing surface roughness or decreasing film thickness. To study the effect of solidification, the impact of molten tin droplets (0.6 mm diameter) on solid surfaces was observed for a range of impact velocities (10 to 30 m/s), substrate temperatures (25 to 200°C) and substrate materials (stainless steel, aluminum and glass) using the rotating flywheel apparatus. Droplets splashed extensively on a cold surface but on a hot surface there was no splashing. Splashing could be completely suppressed by either increasing the substrate temperature or reducing its thermal diffusivity. An analytical model was developed to predict this splashing behavior. The above two theories of freezing-induced splashing and film rupture were combined to predict the morphology of splats typically observed in a thermal spray process. A dimensionless solidification parameter, which takes into account factors such as the droplet diameter and velocity, substrate temperature, splat and substrate thermophysical properties, and thermal contact resistance between the two, was developed. Predictions from the model were compared with a wide range of experimental data and found to agree well.

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 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 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 Handbook of Atomization and Sprays written by Nasser Ashgriz and published by Springer Science & Business Media. This book was released on 2011-02-18 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomization and sprays are used in a wide range of industries: mechanical, chemical, aerospace, and civil engineering; material science and metallurgy; food; pharmaceutical, forestry, environmental protection; medicine; agriculture; meteorology and others. Some specific applications are spray combustion in furnaces, gas turbines and rockets, spray drying and cooling, air conditioning, powdered metallurgy, spray painting and coating, inhalation therapy, and many others. The Handbook of Atomization and Sprays will bring together the fundamental and applied material from all fields into one comprehensive source. Subject areas included in the reference are droplets, theoretical models and numerical simulations, phase Doppler particle analysis, applications, devices and more.

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 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.

Download or read book Droplet Impact on Deep Liquid Pools written by Eduardo A. Castillo Orozco and published by . This book was released on 2015 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: This could result in jet breakup and formation of secondary drops. In other words, both the formation of the jet and its breakup require a balance between viscous, capillary and surface tension forces. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested for 0.0033 [less than or equal to] Oh [less than or equal to] 0.136. For Weber numbers beyond the critical value and Oh [less than or equal to] 0.091 the jet breakup occurs (Rayleigh jet breakup regime). While for Oh [greater than] 0.091, the jet breakup is suppressed regardless of the Weber number. In addition, high impact velocity initiates the crown formation and if further intensified it can disintegrate it into numerous secondary drops (crown splash) and it is observed to occur at all Ohnesorge numbers and high enough Weber numbers, however, at high Oh, a large portion of kinetic energy is dissipated, thus Rayleigh jet breakup is suppressed regardless of the magnitude of the impact velocity. Moreover, a correlation is proposed for normalized time with respect to the normalized maximum height of jet.

Download or read book Recent Trends in Thermal and Fluid Sciences written by Achhaibar Singh and published by Springer Nature. This book was released on with total page 429 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Science and Engineering of Droplets written by Huimin Liu and published by William Andrew. This book was released on 1999-12-31 with total page 541 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to encompass the fundamental phenomenon, principles, and processes of discrete droplets of both normal liquids and melts. It provides the reader with the science and engineering of discrete droplets, and provides researchers, scientists and engineers with the latest developments in the field. The book begins with a systematic review of various processes and techniques, along with their applications and associations with materials systems. This is followed by a description of the phenomena and principles in droplet processes. Correlations, calculations, and numerical modeling of the droplet processes provide insight into the effects of process parameters on droplet properties for optimization of atomizer design. Droplets are found in the areas of metallurgy, materials, automotive, aerospace, medicine, food processing, agriculture, and power generation, and encountered in a huge range of engineering applications.

Download or read book Droplets Sprays and Aerosols written by Nasser Ashgriz and published by Independently Published. This book was released on 2022-08-25 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a theoretical description of the liquid atomization and spray formation. It is the first in series of books on droplets, sprays and aerosol. The atomization process is a combination of several different liquid breakup processes. It involves of the formation of waves on the liquid surface, which are generated by a variety of effects, such as by the large relative velocity between the liquid and its surrounding gas. The waves may grow in amplitude, stretch out of the core liquid flow, and eventually breakup into cylindrical or sheet-like ligaments. Liquid ligaments may become unstable and breakup into droplets. Droplets may deform and breakup into smaller droplets by the drag forces or by collision with other droplets or solid surfaces. The physical principal behind the above processes can be simplified into several liquid instability processes. These include instabilities of liquid sheets, jets, and droplets. These instabilities are mainly governed by Kelvin-Helmholtz, Rayleigh-Plateau, and Rayleigh-Taylor instabilities, which respectively come about due to a velocity difference between the liquid and its surrounding gas; due to capillary forces, and by the acceleration of one fluid onto the other. Droplet-droplet collisions and droplet impact on solid surfaces are two other important processes that occur in sprays. Droplets may coalesce after collision forming larger droplets or breakup into smaller droplets. Phenomenological models are used to provide droplet sizes that emerge. Similarly, when a droplet impacts on a solid surface, it may spread, splash, or bounce off. Models for the relevant outcomes to atomization are provided for this process. Finally, the atomization processes is modeled by combining various instability theories to obtain characteristic droplet sizes for different types of spray.

Download or read book Modern Tribology Handbook Two Volume Set written by Bharat Bhushan and published by CRC Press. This book was released on 2000-12-28 with total page 1760 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent research has led to a deeper understanding of the nature and consequences of interactions between materials on an atomic scale. The results have resonated throughout the field of tribology. For example, new applications require detailed understanding of the tribological process on macro- and microscales and new knowledge guides the rational

Download or read book Physics of Wetting written by Edward Yu. Bormashenko and published by Walter de Gruyter GmbH & Co KG. This book was released on 2017-09-11 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: Motivated by a plethora of phenomena from nature, this textbook introduces into the physics of wetting of surfaces. After a brief discussion of the foundations of surface tension, its implementation for floating objects, capillary waves, bouncing droplets, walking of water striders, etc. is discussed. Furthermore, Marangoni flows, surface tension inspired instabilities, condensation and evaporation of droplets, liquid marbles, superhydrophobicity and superoleophobicity (lotus effect) are introduced. All relevant concepts are illustrated by the numerous qualitative and quantitative exercises. Contents What is surface tension? Wetting of surfaces: the contact angle Surface tension-assisted floating of heavy and light objects and walking of water striders Capillary interactions between particles. Particles placed on liquid surfaces. Elasticity of liquid surfaces, covered by colloidal particles Capillary waves Oscillation of droplets Marangoni flow and surface instabilities Evaporation of droplets. The Kelvin and the coffee-stain effects Condensation, growth and coalescence of droplets and the breath-figure self-assembly Dynamics of wetting: bouncing, spreading and rolling of droplets (water hammer effect – water entry and drag-out problems)Superhydrophobicity and superoleophobicity: the Wenzel and Cassie wetting regimes The Leidenfrost effect. Liquid marbles: self-propulsion Physics, geometry, life and death of soap films and bubbles

Download or read book A Study of Splashes written by A.M. Worthington and published by BoD – Books on Demand. This book was released on 2018-04-05 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reproduction of the original: A Study of Splashes by A.M. Worthington

Download or read book Thermal Spray written by International Thermal Spray Conference and published by ASM International. This book was released on 1998-01-01 with total page 1658 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 2016-04-19 with total page 344 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

Download or read book Handbook of Numerical Simulation of In Flight Icing written by Wagdi George Habashi and published by Springer Nature. This book was released on 2024-01-12 with total page 1278 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Handbook of Numerical Simulation of In-Flight Icing covers an array of methodologies and technologies on numerical simulation of in-flight icing and its applications. Comprised of contributions from internationally recognized experts from the Americas, Asia, and the EU, this authoritative, self-contained reference includes best practices and specification data spanning the gamut of simulation tools available internationally that can be used to speed up the certification of aircraft and make them safer to fly into known icing. The collection features nine sections concentrating on aircraft, rotorcraft, jet engines, UAVs; ice protection systems, including hot-air, electrothermal, and others; sensors and probes, CFD in the aid of testing, flight simulators, and certification process acceleration methods. Incorporating perspectives from academia, commercial, government R&D, the book is ideal for a range of engineers and scientists concerned with in-flight icing applications.