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Author: Nithin S. Panicker Publisher: ISBN: Category : Languages : en Pages : 82
Book Description
Numerical investigation of the flow in a drop of a dielectric fluid suspended in another immiscible dielectric fluid in the presence of an alternating electric field has been carried out. When an electric field is applied to a drop of a dielectric fluid, the electric field induces stresses at the fluid interface. The normal stresses deform the drop and the tangential stresses produce a circulatory motion inside and outside the drop. Such electrical field induced flow can lead to significant enhancement of heat or mass transfer to from the drop. A stream function-vorticity approach with a finite volume formulation is adopted to numerically determine the unsteady flow field in the continuous and the dispersed phases. The volume of fluid (VOF) method is used to track the phase boundary and to predict the transient drop shape deformations for a range of capillary numbers. A new VOF formulation with Continuum Surface Force model has been derived and implemented to account for both the tangential and the normal electrical stresses present at the phase interface. Results show that the extent of drop deformation increases with capillary number and the strength of the electric field. By tracking Lagrangian fluid particles inside the deforming droplet, it is seen that the changing flow patterns due to drop deformation lead to significant fluid mixing inside the droplet. Earlier studies available in the literature neglect drop deformations and may significantly underestimate the heat/mass transfer enhancement in the presence of an alternating electric field.
Author: Nithin S. Panicker Publisher: ISBN: Category : Languages : en Pages : 82
Book Description
Numerical investigation of the flow in a drop of a dielectric fluid suspended in another immiscible dielectric fluid in the presence of an alternating electric field has been carried out. When an electric field is applied to a drop of a dielectric fluid, the electric field induces stresses at the fluid interface. The normal stresses deform the drop and the tangential stresses produce a circulatory motion inside and outside the drop. Such electrical field induced flow can lead to significant enhancement of heat or mass transfer to from the drop. A stream function-vorticity approach with a finite volume formulation is adopted to numerically determine the unsteady flow field in the continuous and the dispersed phases. The volume of fluid (VOF) method is used to track the phase boundary and to predict the transient drop shape deformations for a range of capillary numbers. A new VOF formulation with Continuum Surface Force model has been derived and implemented to account for both the tangential and the normal electrical stresses present at the phase interface. Results show that the extent of drop deformation increases with capillary number and the strength of the electric field. By tracking Lagrangian fluid particles inside the deforming droplet, it is seen that the changing flow patterns due to drop deformation lead to significant fluid mixing inside the droplet. Earlier studies available in the literature neglect drop deformations and may significantly underestimate the heat/mass transfer enhancement in the presence of an alternating electric field.
Author: Osameh Ghazian Publisher: ISBN: Category : Languages : en Pages :
Book Description
Electric field induced flows, or electrohydrodynamics (EHD), have been promising in many fast-growing technologies, where droplet movement and deformation can be controlled to enhance heat transfer and mass transport. Several complex EHD problems existing in many applications were investigated in this thesis. Firstly, this thesis presents the results of numerical simulations of the deformation, oscillation and breakup of a weakly conducting droplet suspended in an ambient medium with higher conductivity. It is the first time that the deformation of such a droplet was investigated numerically in a 3D configuration. We have determined three types of behavior for the droplets, which are less conducting than ambient fluid: 1) oblate deformation (which can be predicted from the small perturbation theory), 2) oscillatory oblate-prolate deformation and 3) breakup of the droplet. Secondly, a numerical study of droplet oscillation placed on different hydrophobic surfaces under the effect of applied AC voltage including the effect of ambient gas was investigated. The presented algorithm could reproduce droplet oscillations on a surface considering different contact angles. It has been found that the resonance frequency of the water droplet depends on the surface property of the hydrophobic materials and the electrostatic force. Thirdly, a new design of an electrowetting mixer using the rotating electric field was proposed which offers a new method to effectively mix two droplets over a different range of AC frequencies. Two regimes were observed for droplet coalescence: 1) coalescence due to the high droplet deformation, 2) coalescence due to the interaction of electrically induced dipoles. Fourthly, the spreading and retraction control of millimetric water droplets impacting on dry surfaces have been investigated to examine the effect of the surface charge density and electric field intensity. The effect of the surface charge on the spreading of droplets placed gently on surfaces was investigated in the first part. It was found that the maximum spreading diameter increases with an increasing charge. In the second part, the impact of a droplet on a ground electrode was considered. It was also found that in order to keep the maximum diameter after the impact, less charge is needed for surfaces with lower contact angle. Finally, the interaction between two identical charged droplets was investigated numerically. The effects of the impact velocity, drop size ratio and electric charge on the behavior of the combined droplet were investigated. It was shown that two conducting droplets carrying charges of the same polarity under some conditions may be electrically attracted. The formation of charged daughter droplets has been investigated and it was found that the number of the satellite droplets after collision appears to increase with an increase in the droplet charge.
Author: Publisher: ISBN: Category : Engineering Languages : en Pages : 2264
Book Description
Since its creation in 1884, Engineering Index has covered virtually every major engineering innovation from around the world. It serves as the historical record of virtually every major engineering innovation of the 20th century. Recent content is a vital resource for current awareness, new production information, technological forecasting and competitive intelligence. The world?s most comprehensive interdisciplinary engineering database, Engineering Index contains over 10.7 million records. Each year, over 500,000 new abstracts are added from over 5,000 scholarly journals, trade magazines, and conference proceedings. Coverage spans over 175 engineering disciplines from over 80 countries. Updated weekly.
Author: Rumiana Dimova Publisher: CRC Press ISBN: 1498752187 Category : Science Languages : en Pages : 652
Book Description
Giant vesicles are widely used as a model membrane system, both for basic biological systems and for their promising applications in the development of smart materials and cell mimetics, as well as in driving new technologies in synthetic biology and for the cosmetics and pharmaceutical industry. The reader is guided to use giant vesicles, from the formation of simple membrane platforms to advanced membrane and cell system models. It also includes fundamentals for understanding lipid or polymer membrane structure, properties and behavior. Every chapter includes ideas for further applications and discussions on the implications of the observed phenomena towards understanding membrane-related processes. The Giant Vesicle Book is meant to be a road companion, a trusted guide for those making their first steps in this field as well as a source of information required by experts. Key Features • A complete summary of the field, covering fundamental concepts, practical methods, core theory, and the most promising applications • A start-up package of theoretical and experimental information for newcomers in the field • Extensive protocols for establishing the required preparations and assays • Tips and instructions for carefully performing and interpreting measurements with giant vesicles or for observing them, including pitfalls • Approaches developed for investigating giant vesicles as well as brief overviews of previous studies implementing the described techniques • Handy tables with data and structures for ready reference
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 804
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Nithin S. Panicker
Author: Nithin S. Panicker
Author: Osameh Ghazian
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