Download or read book Characteristics of Thin Liquid Films Flow on Inclined Surfaces written by Gil Ingel and published by . This book was released on 1981 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thin Liquid Films written by Ralf Blossey and published by Springer Science & Business Media. This book was released on 2012-05-22 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a treatise on the thermodynamic and dynamic properties of thin liquid films at solid surfaces and, in particular, their rupture instabilities. For the quantitative study of these phenomena, polymer thin films (sometimes referred to as “ultrathin”) have proven to be an invaluable experimental model system. What is it that makes thin film instabilities special and interesting? First, thin polymeric films have an important range of applications. An understanding of their instabilities is therefore of practical relevance for the design of such films. The first chapter of the book intends to give a snapshot of current applications, and an outlook on promising future ones. Second, thin liquid films are an interdisciplinary research topic, which leads to a fairly heterogeneous community working on the topic. It justifies attempting to write a text which gives a coherent presentation of the field which researchers across their specialized communities might be interested in. Finally, thin liquid films are an interesting laboratory for a theorist to confront a well-established theory, hydrodynamics, with its limits. Thin films are therefore a field in which a highly fruitful exchange and collaboration exists between experimentalists and theorists. The book stretches from the more concrete to more abstract levels of study: we roughly progress from applications via theory and experiment to rigorous mathematical theory. For an experimental scientist, the book should serve as a reference and guide to what is the current consensus of the theoretical underpinnings of the field of thin film dynamics. Controversial problems on which such a consensus has not yet been reached are clearly indicated in the text, as well as discussed in a final chapter. From a theoretical point of view, the field of dewetting has mainly been treated in a mathematically ‘light’ yet elegant fashion, often making use of scaling arguments. For the untrained researcher, this approach is not always easy to follow. The present book attempts to bridge between the ‘light’ and the ‘rigorous’, always with the ambition to enhance insight and understanding - and to not let go the elegance of the theory.

Download or read book Falling Liquid Films written by S. Kalliadasis and published by Springer Science & Business Media. This book was released on 2011-09-24 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: Falling Liquid Films gives a detailed review of state-of-the-art theoretical, analytical and numerical methodologies, for the analysis of dissipative wave dynamics and pattern formation on the surface of a film falling down a planar inclined substrate. This prototype is an open-flow hydrodynamic instability, that represents an excellent paradigm for the study of complexity in active nonlinear media with energy supply, dissipation and dispersion. It will also be of use for a more general understanding of specific events characterizing the transition to spatio-temporal chaos and weak/dissipative turbulence. Particular emphasis is given to low-dimensional approximations for such flows through a hierarchy of modeling approaches, including equations of the boundary-layer type, averaged formulations based on weighted residuals approaches and long-wave expansions. Whenever possible the link between theory and experiment is illustrated, and, as a further bridge between the two, the development of order-of-magnitude estimates and scaling arguments is used to facilitate the understanding of basic, underlying physics. This monograph will appeal to advanced graduate students in applied mathematics, science or engineering undertaking research on interfacial fluid mechanics or studying fluid mechanics as part of their program. It will also be of use to researchers working on both applied, fundamental theoretical and experimental aspects of thin film flows, as well as engineers and technologists dealing with processes involving isothermal or heated films. This monograph is largely self-contained and no background on interfacial fluid mechanics is assumed.

Download or read book Characteristics and Applications of Thin Liquid Films Flowing Down High Curvature Surfaces written by Abolfazl Sadeghpour and published by . This book was released on 2020 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin liquid films flowing down vertical fibers present a wealth of complex and interesting interfacial dynamics, including the formation of droplets and traveling wave patterns. Such dynamics is an important consideration in various applications, such as fiber coating and direct-contact heat and mass exchangers which take advantage of extended interfacial areas and larger residence time afforded by the bead formation along the fiber. A rigorous investigation on the fluid dynamics and interfacial heat and mass transfer mechanism of liquid films flowing along vertical strings is, thus, needed to enable physics-based optimization and analysis of multi-string designs for the mentioned applications. This dissertation presents a combination of experimental, numerical, and theoretical study of liquid films flowing down a vertical fiber. Additionally, we report a first-ever combined experimental and theoretical study of the instability in thin film flows of a high-surface energy low-viscosity liquid (i.e. water) along cotton threads. Utilizing our finding, we then adapted the multi-string configuration for novel applications, such as humidification, dehumidification, and particle capturing. We started with a thorough experimental study of viscous liquids flowing down vertical fibers (i.e. polymer strings). Previous researchers suggested that the liquid film thickness and velocity profiles of nearly flat portion of a liquid film that precedes the onset of instability can be specified regardless of the nozzle geometry. As a result, they largely overlooked the effects of nozzle on the pattern and characteristics of the downstream flow. We performed a systematic experimental study by varying the nozzle inner diameter from 0.5 to 3.2 mm at various mass flow rates (from 0.02 to 0.08 g/s). We focused on experimental conditions within the Rayleigh Plateau (RP) instability regime, where traveling wave solution emerges and generates uniformly-spaced drop-like liquid beads on vertical fibers. Our results emphasize the strong influence of nozzle geometry on the flow regime and the flow characteristics. We experimentally measured the thickness of the flat film portion after the nozzle, which we term the preinstability thickness, and identified it as a flow parameter which governs the size, spacing, and velocity of downstream liquid beads. We also performed a set of complementary numerical simulations that solves the full Navier-Stokes equations to predict the fluid dynamics of the downstream flow, such as the liquid velocity profile along the fiber. To better understand the influence of nozzle diameter on the regime transition as well as the downstream bead dynamics, we performed a detailed theoretical study of viscous flow down a vertical fiber. We proposed a full lubrication model that includes slip boundary conditions, nonlinear curvature terms, and a film stabilization term, and compared the predicted film dynamics against the experimental results. Numerical simulations confirm that in addition to fiber sizes and flow rates, the downstream flow regime and characteristics are also significantly affected by the nozzle geometry. Moreover, the effect of film stabilization term on the flow pattern and bead characteristic is studied. We also compared our results with previously studied theoretical methods, such as CM model, linear curvature model, and full curvature model. Additionally, we leveraged our successful demonstration of stable water flow along a vertical cotton string to construct a multi-string water vapor capturing system, where a massive array traveling water beads act as the condensation interface for water vapor in the counterflowing air stream. These water beads form through intrinsic flow instability and offer high curvature surfaces to enhance the vapor condensation rate. The effects of the water flow rate and air velocity on the condensation rates are experimentally characterized. The gas-stream pressure drop of the design is also measured. The condensation rates and gas-stream pressure drop from our multi-string dehumidifier is compared with the existing dehumidifier designs. A simplified theoretical model is also presented as the starting point for further optimizing the design parameters of our device. Finally, we extended our investigation for potential applications of the cotton-based multi-string configuration and proposed a novel string-based particle collector. Wet electrostatic precipitators (WESP) are generally highly effective for collecting fine particles in air streams from various sources such as diesel engines, power plants, and oil refineries. However, some limiting factors, such as high water usage, poses restrictions. Our new compact particle collector utilizes an array of traveling water beads on vertical cotton strings to collect the pre-charged particles in the counterflowing air stream. The experimental and numerical investigation presented in this work is performed to determine the collection efficiency and the optimal water flow rate for our new design. The unique configuration of our string-based counterflow WESP in this study exhibits high number-based collection efficiency, > 80%, for a wide range of particle diameters, 10 nm - 2.5 m, while decreasing the water usage significantly, which can provide a basis for the design of more water-efficient WESPs.

Download or read book Conceptual Models of Flow and Transport in the Fractured Vadose Zone written by National Research Council and published by National Academies Press. This book was released on 2001-05-21 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid flow and solute transport within the vadose zone, the unsaturated zone between the land surface and the water table, can be the cause of expanded plumes arising from localized contaminant sources. An understanding of vadose zone processes is, therefore, an essential prerequisite for cost-effective contaminant remediation efforts. In addition, because such features are potential avenues for rapid transport of chemicals from contamination sources to the water table, the presence of fractures and other channel-like openings in the vadose zone poses a particularly significant problem, Conceptual Models of Flow and Transport in the Fractured Vadose Zone is based on the work of a panel established under the auspices of the U.S. National Committee for Rock Mechanics. It emphasizes the importance of conceptual models and goes on to review the conceptual model development, testing, and refinement processes. The book examines fluid flow and transport mechanisms, noting the difficulty of modeling solute transport, and identifies geochemical and environmental tracer data as important components of the modeling process. Finally, the book recommends several areas for continued research.

Download or read book Thin Liquid Films written by Ivan Ivanov and published by Taylor & Francis. This book was released on 2023-02-06 with total page 1141 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive reference provided a systematic examination of both the theory and applications of thin liquid films - giving a critical review of major concepts and unresolved or controversial problems, as well as revealing experimental methods. It includes results previously unpublished. Combining the work of 20 leading researchers, Thin Liquid Films furnishes a fundamental overview of thermodynamics of thin liquid films. Generously illustrated with equations, tables and drawling and containing more than 2,200 citations to pertinent literature, this is an authoritative reference for physical, surface, and colloid chemists, biophysicists and physicists; chemical engineers and advanced graduate students in chemistry, chemical engineering, biophysics and physics.

Download or read book The Characteristics of a Thin Liquid Film on a Spinning Disk written by Carl Gazley and published by . This book was released on 1968 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of thin liquid films on a spinning disk is described. Such films are characterized by large values of the ratio of interfacial area to liquid volume, can be formed in very small equipment compared to falling films, and their development is independent of surface orientation to the gravitational field. This makes them interesting for a number of energy and mass transfer processes. The paper summarizes the available numerical and analytical studies of the fluid-mechanical characteristics of spinning films and presents measurements of average film thickness as a function of radial position, liquid flow rate, and rotational speed. In spite of surface-tension phenomena (waves, dry spots, etc.) not accounted for in the theoretical study, the data indicate that the theory predicts the proper relative effects of the several variables. (Author).

Download or read book Partial Differential Equations of Thin Liquid Films Analysis and Numerical Simulation written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We consider four problems related to Marangoni-driven thin liquid films. The first compares two models for the motion of a contact line: the precursor model and the Navier slip model. We restrict attention to traveling wave solutions of the thin film PDE for a film driven up an inclined planar solid surface by a thermally induced surface tension gradient. The range of effective contact slopes and parameter values are explained with the aid of Poincaré sections of the phase diagram of the third order ODE. In the second problem, we use theory from hyperbolic conservation laws to map classical shocks, nonclassical shock waves (known as undercompressive shocks) and rarefactions that arise as solutions to the Cauchy problem. To create such a 'Riemann map', we employ a kinetic relation that describes admissible nonclassical shock waves, and a nucleation condition that determines when a nonclassical solution is selected. The hyperbolic theory captures features observed in thin film flow, such as multiple long-time solutions for the same initial upstream and downstream states. The third problem incorporates localized heating by an infrared (IR) laser to the model of a Marangoni-driven thin film from the previous problems. We analyze two types of steady state solutions, using a dynamical systems approach to explain homoclinic solutions and PDE simulations to explain heteroclinic solutions. We discuss several methods for controlling the downstream height and the strength of forcing required to create homoclinic solutions from uniform or monotonic initial data. The fourth problem explores a model for a different physical scenario, in which a thin film is driven down a solid substrate by gravity and surfactant. The model couples the thin film PDE for the height of the film with an equation for the transport of surfactant. Solutions of the parabolic-hyperbolic system include a complicated [em double wave solution], with discontinuities in the height and surfactant concentra.

Download or read book Advances in Two Phase Flow and Heat Transfer written by Sadik Kakaç and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past two decades, two-phase flow and heat transfer problems associated with two-phase phenomena have been a challenge to many investigators. Two-phase flow applications are found in a wide range of engineering systems, such as nuclear and conventional power plants, evaporators of refrigeration systems and a wide vari ety of evaporative and condensive heat exchangers in the chemical industry. This publication is based on the invited lectures presented at the NATO Advanced Research Workshop on the Advances in Two-Phase Flow and Heat Transfer. The Horkshop was attended by more than 50 leading scientists and practicing engineers who work actively on two-phase flow and heat transfer research and applications in dif ferent sectors (academia, government, industry) of member countries of NATO. Some scientific leaders and experts on the subject matter from the non-NATO countries were also invited. They convened to discuss the state-of-the-art in two-phase flow and heat transfer and formulated recommendations for future research directions. To achieve these goals, invited key papers and a limited number of contributions were presented and discussed. The specific aspects of the subject were treated in depth in the panel sessions, and the unresolved problems identified. Suitable as a practical reference, these volumes incorporate a systematic approach to two-phase flow analysis.

Download or read book Laminar Flow of Thin Liquid Films Around Solid Bodies of Various Shapes written by Nabil Abdelal Hassan and published by . This book was released on 1963 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Instabilities and Breakup in Thin Liquid Films written by Vineeth Chandran Suja and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid films having dimensions that are relatively small in the direction normal to their surface are commonly referred to as thin liquid films. Due to their prevalence in nature and due to their unique geometrical characteristics, a comprehensive understanding of thin film dynamics including instabilities and break-up within thin liquid films is of fundamental and practical interest. Practically this understanding is crucial to tuning the stability thin films in a number of important applications such as for stabilizing foams in foods and beverages, destabilizing foams in lubricants, avoiding surface irregularities in liquid coatings and treating ophthalmic disorders originating from the unnatural breakup of the tear film. Fundamentally, the microscopic thickness of these liquid films along with their large surface to volume ratio presents a convenient framework to investigate characteristics of two dimensional flows, and probe the effects of surface phenomenon such as evaporation and surfactant dynamics on fluid flows. Motivated by the importance of thin liquid films, in this thesis, we experimentally investigate the instabilities and break-up within thin liquid films. In the first part of the thesis (Chapters 2 - 4), we develop and optimize experimental tools and protocols for systematically studying thin liquid films. Notably, we show that single bubble/drop experiments are a convenient and complementary technique to study the dynamics of thin liquid films. Subsequently, we detail a new technique for automatically and robustly measuring the spatiotemporal thickness of thin liquid films - hyperspectral interferometry coupled with machine learning. Finally, we will also establish the operating regimes within which the size of bubbles formed on capillaries for single bubble experiments can be precisely controlled to avoid an air compressibility driven shape instabilities. In the subsequent parts of the thesis we utilize the developed tools to study four different problems - Bubble stability in worm like micellar (WLM) polymer solutions (Chapter 5), Lubricant foaming (Chapters 6 - 8), Drying of thin polymer films (Chapter 9) and Dewetting of the tear film (Chapter 10). In Chapter 5, we explore a problem relevant for the cosmetic industry, and characterize the drainage characteristics of thin films between bubbles and flat wormlike micellar solution - air interfaces. The supramolecular structure and elasticity of the wormlike micelles alters the dynamics of film drainage in WLM as compared to those in thin films containing pure surfactants. The unique features of film drainage include film elasticity driven 'dimple recoil' and a single step transition to a Newton black film beyond a critical film thickness. In Chapters 6 - 8, we explore a problem relevant for the lubricant industry, and study the stability of thin liquid films in lubricants with and without antifoams. Utilizing single bubble experiments, we reveal that the stability of thin films between bubbles in lubricant base oils are enhanced by Marangoni flows driven by the differential evaporation of the various components in the oil. Fundamentally, we also show that the spatiotemporal characteristics of these Marangoni flows are regulated by the concentration and volatility of the volatile species in the oil. Interestingly when the concentration of the volatile species approaches 50%, evaporation driven Marangoni flows become chaotic, with disordered spatial structure, chaotic fluctuations, spatially invariant mean film thickness statistics, high sensitivity to initial conditions, rapidly decaying spatial correlation and a power spectrum for thickness fluctuation that obeys a power law scaling that closely resembles the Kolmogorov's -5/3rd scaling. In the presence of filtered lubricants with antifoams, we reveal that the stability of thin films are positively correlated to the number of filtration cycles, and inversely correlated to the nominal filter pore size and the initial antifoam concentration. In Chapter 9 we explore a problem relevant for film coating, and study the drying of aqueous polymer solutions. Depending on the polymer concentration and the polymer diffusivities, we show that a classical Rayleigh-Taylor instability can develop within the drying solution. We also present the scaling laws describing the onset time of the instability as a function of the physical properties and initial polymer concentrations of the solutions. In Chapter 10 we report a platform to characterize the thickness of the tear film in vivo. By qualitatively comparing the dewetting characteristics observed in vivo with in vitro experiments, we will show that the mechanisms of dewetting is influenced by the presence of interfacial rheology. Further we also reveal that the spatial locations that are prone to dewetting are determined by the presence of interfacial rheology and the spatiotemporal drainage characteristics of the tear film. In Chapter 11 we summarize the findings in this thesis and discuss a number of interesting venues for future research.

Download or read book Encyclopedia of Chemical Processing written by Sunggyu Lee and published by Taylor & Francis US. This book was released on 2006 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt: Collecting information of vital interest to chemical, polymer, mechanical, electrical, and civil engineers, as well as chemists and chemical researchers, this "Encyclopedia "supplies nearly 350 articles on current design, engineering, science, and manufacturing practices-offering expertly written articles on technologies at the forefront of the field to maximize and enhance the research and production phases of current and emerging chemical manufacturing practices and techniques.

Download or read book Thinning and Rupture of a Thin Liquid Film on a Heated Surface written by and published by . This book was released on 1992 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this work continues to be the study of dynamics, stability, and rupture (including contact line motions) of thin liquid films, especially with heat and/or mass transfer. Following the publication of a comprehensive paper on thin-film stability and rupture, taking into account evaporation (condensation), thermocapillarity, surface tension, vapor recoil, van der Waals forces, and mass loss (gain), two follow-up papers have appeared. The first examines the conditions for a non-uniformly-heated liquid film to rupture, owing to thermocapillarity, while the second reports experimental results in excellent agreement with the theory on non-isothermal free-surface problems. Another paper extends some previous results to the case where the viscosity of the liquid is a function of temperature. By proper rescaling, it is shown that the evolution equation can be transformed into the constant-viscosity case, so that previous results can be applied directly. Another paper considers the nonlinear growth, steepening, and wavebreaking of an isothermal thin liquid film draining down an inclined plate. The competition between mean flow and evaporation gives important morphological changes that control the heat-transfer process in the wavy regime. A number of other results were obtained. 9 refs.

Download or read book Dynamics of Thin Liquid Films written by Vilhjalmur Ludviksson and published by . This book was released on 1968 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Nonlinear Dynamics written by Walter Lacarbonara and published by Springer Nature. This book was released on 2022-03-18 with total page 891 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first of three volumes includes papers from the second series of NODYCON, which was held virtually in February of 2021. The conference papers reflect a broad coverage of topics in nonlinear dynamics, ranging from traditional topics from established streams of research to those from relatively unexplored and emerging venues of research. These include Fluid-structure interactions Mechanical systems and structures Computational nonlinear dynamics Analytical techniques Bifurcation and dynamic instability Rotating systems Modal interactions and energy transfer Nonsmooth systems

Download or read book Stable Localized Patterns in Thin Liquid Films written by Robert J. Deissler and published by . This book was released on 1991 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book FLOW IN THIN LIQUID FILMS written by P. C. Scholten and published by . This book was released on 1962 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: An improved experimental method for studying vertical soap films slowly pulled out of a solution is described and the interpretation of the optical thickness measurements is discussed. The behavior of mobile films presents complications which are described. Rigid films on the other hand give results for films thicker than 800 1100 Angstroms, which agree very closely with Frankel's law relating film thickness to the velocity of pull-out. Since Frankel's law is derived on the assumption that the viscosity is constant up to the monolayer, this agreement proves the absence of any thick rigidified water layers (or of slip) in the neighborhood of the surface. (Author).