Effect of Surfactant Transport on the Mobility of Bubbles in Liquids PDF Download

Author: Ravichandra Palaparthi
Publisher:
ISBN:
Category : Bubbles
Languages : en
Pages : 368

View

Book Description

Author: Yanping Wang
Publisher:
ISBN:
Category : Bubbles
Languages : en
Pages : 226

View

Book Description
We examine the effect of surfactants on a spherical gas bubble rising steadily in an infinite fluid at low and order one Reynolds number with order one and larger Peclet numbers. Our mathematical model is based on the Navier-Stokes equations coupled with a convection-diffusion equation together with appropriate interfacial conditions. The nonlinearity of the equations and boundary conditions, and the coupling between hydrodynamics and surfactant transport make the problem very challenging. When a bubble rises in a fluid containing surface-active agents, surfactant adsorbs onto the bubble surface at the leading edge, convects to the trailing edge by the surface flow and desorbs into the bulk along the interface. This adsorption develops a surface concentration gradient on the interface that makes the surface tension at the back end relatively lower than that at the front end, and thus retards the bubble velocity. Because of surfactant impurities unavoidably present in materials, this retardation can cause a problem in materials processing in space and glass processing when bubbles are created during chemical reactions. Thus the study of how to remobilize (remove the surfactant gradient on the surface) the bubble surface becomes necessary. Many studies have been done on this retarding effects of the surfactant on a moving bubble. However, most were focused on the retarding effect due to a trace amount of surfactant, in which case the bubble velocity monotonically decreases as the bulk concentration increases. The question of how to remobilize the bubble surface remains unanswered. In this work, we will show that the bubble velocity can be controlled by remobilizing the bubble interface using the surfactant concentration. This technique not only can be used to maximize the bubble velocity, but also can be used to maximize mass transfer on purifying materials and extracting materials from mixtures. In the first part of the work, we illustrate numerically that the bubble interface can be remobilized by increasing the bulk concentration of surfactant, for any fixed Peclet number, at low Reynolds number. For any fixed bulk concentration, the bubble velocity decreases with increasing Peclet number. The larger the Peclet number is the larger the required bulk concentration needed to bring the velocity back to the clean surface value. In the second part of the work, we will show that the remobilization still remains effective for order one Reynolds numbers. Moreover, when the rate of convection on the surface is much larger than the rate of diffusion at the back end, a stagnant cap develops near the back stagnation point that makes the bubble surface there act like a solid boundary. Wakes form at higher Reynolds numbers that drastically reduce the terminal velocity, and disappear as the bubble interface remobilizes. Finally, we consider the problem analytically for asymptotically large Peclet numbers. When the Peclet number is very large, a stagnant cap forms at the back end which makes one part of the bubble surface clean of surfactant, and the other part completely immobile. Also boundary layers develop along the bubble surface with different thicknesses on the clean part of the surface and on the stagnant cap. The asymptotic structures are obtained and the governing equations posed and partly addressed numerically and analytically.

Author: Z. Zapryanov
Publisher: Springer Science & Business Media
ISBN: 9401592551
Category : Technology & Engineering
Languages : en
Pages : 527

View

Book Description
1. Objective and Scope Bubbles, drops and rigid particles occur everywhere in life, from valuable industrial operations like gas-liquid contracting, fluidized beds and extraction to such vital natural processes as fermentation, evaporation, and sedimentation. As we become increasingly aware of their fundamental role in industrial and biological systems, we are driven to know more about these fascinating particles. It is no surprise, therefore, that their practical and theoretical implications have aroused great interest among the scientific community and have inspired a growing number of studies and publications. Over the past ten years advances in the field of small Reynolds numbers flows and their technological and biological applications have given rise to several definitive monographs and textbooks in the area. In addition, the past three decades have witnessed enormous progress in describing quantitatively the behaviour of these particles. However, to the best of our knowledge, there are still no available books that reflect such achievements in the areas of bubble and drop deformation, hydrodynamic interactions of deformable fluid particles at low and moderate Reynolds numbers and hydrodynamic interactions of particles in oscillatory flows. Indeed, only one more book is dedicated entirely to the behaviour of bubbles, drops and rigid particles ["Bubbles, Drops and Particles" by Clift et al. (1978)] and the authors state its limitations clearly in the preface: "We treat only phenomena in which particle-particle interactions are of negligible importance. Hence, direct application of the book is limited to single-particle systems of dilute suspensions.

Author: Sven Kastens
Publisher: Cuvillier Verlag
ISBN: 3736964048
Category : Technology & Engineering
Languages : en
Pages : 190

View

Book Description
Gas / liquid contact apparatuses are widely used in chemical, biochemical or pharmaceutical industry to provide and transfer gas species as reactant from the gaseous phase to pre-dissolved reactants in the liquid phase enabling a preferred reaction. The global and local transport are complex interlinked processes and therefore in practice in reactor design industry, mostly empirically correlated. For a secure control of the overall process and a more efficient reactor design, the local transport processes at gas / liquid interfaces need to be investigated in complexity reduced systems to be understood. Elongated bubbles, Taylor bubbles, in vertical channels 5.5 < D < 8 mm overcome the problem of dynamic shape deformation, complex 3D rise trajectories and they have a volume independent rise velocity, which make them the ideal experiment for reliable and reproducible investigations. Detailed optical measurements of global and local processes via high-speed Shadowgraphy, 2D2C PIV and p-2D LIF give new insights into the dependency of local bubble shape and global terminal rise velocity, establish a Sherwood correlation of shrinking CO2 bubbles in various channel sizes and shows the coupling of local transport phenomena at the bubble interface and the mixing in the wake region.

Author: R. Shankar Subramanian
Publisher: Cambridge University Press
ISBN: 9780521496056
Category : Science
Languages : en
Pages : 492

View

Book Description
This 2001 book provides a thorough review of the motion of bubbles and drops in reduced gravity.

Author: Daniel DeKee
Publisher: CRC Press
ISBN: 9781560329060
Category : Science
Languages : en
Pages : 452

View

Book Description
Describes the advances in the transport phenomena of particles, drops and bubbles in complex fluids. This book contains contributions from experts in areas such as particle deposition in membranes, flow of granular mixtures, food suspensions, foams, electro kinetic and thermo capillary driven flows, and two-phase flows.

Author: R. Clift
Publisher: Courier Corporation
ISBN: 0486317749
Category : Science
Languages : en
Pages : 402

View

Book Description
This volume offers a unified treatment and critical review of the literature related to the fluid dynamics, heat transfer, and mass transfer of single bubbles, drops, and particles. 1978 edition.

Author: Ashim Dutta
Publisher: BoD – Books on Demand
ISBN: 1789846609
Category : Science
Languages : en
Pages : 103

View

Book Description
Surfactants by virtue of their structure form self-assembled organized structures that exhibit fascinating properties useful for a wide range of applications. This book is a compilation of chapters from leading experts highlighting the use of specific surfactants and their functional properties in new and emerging areas of science and technology. The first two chapters of this book discuss the various applications of surfactants, including their use in cosmetics, oil recovery from rocks and mineral processing. Subsequent chapters cover advanced topics like new-generation polymer-based nanoparticles with microbial activity and complex phase systems formed as a result of charge-induced interactions between surfactants, polymers and proteins with potential applications in medical devices. In addition, this book reports for the first time on bio-surfactants extracted from micro-organisms present in the clouds. This report is not the only one of its kind, but it opens up a totally new area of research in terms of an unexplored source of bio-surfactants. It also paves the way for understanding their role in controlling our atmosphere and climate.

Author: Raj P. Chhabra
Publisher: CRC Press
ISBN: 0429522878
Category : Science
Languages : en
Pages : 733

View

Book Description
Provides thorough coverage of the scientific foundations and the latest advances in particle motion in non-Newtonian media. Proveds a new detailed section on the effect of confinement on heat transfer from bluff-bodies Demonstrates how dynamic behavior of single particles can yield useful information for modeling transport processes in complex multiphase flows. Addresses heat transfer in viscoplastic fluids throughout the entire book. Highlights qualitative differences between the response of a Newtonian and non-Newtonian fluids in the complex flows encountered in processing applications

Author: Z. Zapryanov
Publisher: Springer Science & Business Media
ISBN: 0792353471
Category : Technology & Engineering
Languages : en
Pages : 540

View

Book Description
1. Objective and Scope Bubbles, drops and rigid particles occur everywhere in life, from valuable industrial operations like gas-liquid contracting, fluidized beds and extraction to such vital natural processes as fermentation, evaporation, and sedimentation. As we become increasingly aware of their fundamental role in industrial and biological systems, we are driven to know more about these fascinating particles. It is no surprise, therefore, that their practical and theoretical implications have aroused great interest among the scientific community and have inspired a growing number of studies and publications. Over the past ten years advances in the field of small Reynolds numbers flows and their technological and biological applications have given rise to several definitive monographs and textbooks in the area. In addition, the past three decades have witnessed enormous progress in describing quantitatively the behaviour of these particles. However, to the best of our knowledge, there are still no available books that reflect such achievements in the areas of bubble and drop deformation, hydrodynamic interactions of deformable fluid particles at low and moderate Reynolds numbers and hydrodynamic interactions of particles in oscillatory flows. Indeed, only one more book is dedicated entirely to the behaviour of bubbles, drops and rigid particles ["Bubbles, Drops and Particles" by Clift et al. (1978)] and the authors state its limitations clearly in the preface: "We treat only phenomena in which particle-particle interactions are of negligible importance. Hence, direct application of the book is limited to single-particle systems of dilute suspensions.