Download or read book Numerical Simulation of Time dependent Droplet Deformation in an Electric Field written by Graeme M. Supeene and published by . This book was released on 2006 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Deformation of a Droplet in a Stationary Electric Field Using DG written by Nehzat Emamy and published by . This book was released on 2013 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Modeling of Deformation Oscillation Spreading and Collision Characteristics of Droplets in an Electric Field written by Osameh Ghazian and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Numerical Simulation of Droplet Deformation in Convective Flows written by Zheng-Tao Deng and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electro deformation of a Moving Boundary written by Herve Nganguia and published by . This book was released on 2014 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the deformation of a viscous drop and a vesicle immersed in a (leaky) dielectric fluid under an electric field. A number of mathematical tools, both analytical and numerical, are developed for these investigations. The dissertation is divided into three parts. First, a large-deformation model is developed to capture the equilibrium deformation of a viscous spheroidal drop covered with non-diffusing insoluble surfactant under a uniform direct current (DC) electric field. The large- deformation model predicts the dependence of equilibrium spheroidal drop shape on the permittivity ratio, conductivity ratio, surfactant coverage, and the elasticity number. Results from the model are carefully compared against the small-deformation (quasispherical) analysis, experimental data and numerical simulation results in the literature. Moreover, surfactant effects, such as tip stretching and surface dilution effects, are greatly amplified at large surfactant coverage and high electric capillary number. These effects are well captured by the spheroidal model, but cannot be described in the second-order small-deformation theory. The large-deformation spheroidal model is then extended to study the equilibrium deformation of a giant unilamellar vesicle (GUV) under an alternating current (AC) electric field. The vesicle membrane is modeled as a thin capacitive spheroidal shell and the equilibrium vesicle shape is computed from balancing the mechanical forces between the fluid, the membrane and the imposed electric field. Detailed comparison against both experiments and small-deformation theory shows that the spheroidal model gives better agreement with experiments in terms of the dependence on fluid conductivity ratio, electric field strength and frequency, and vesicle size. Asymptotic analysis is conducted to compute the crossover frequency where a prolate vesicle crosses over to an oblate shape, and comparisons show the spheroidal model gives better agreement with experimental observations. Finally, a numerical scheme based on immersed interface method for two-phase fluids is developed to simulate the time-dependent dynamics of an axisymmetric drop in an electric field. The second-order immersed interface method is applied to solving both the fluid velocity field and the electric field. To date this has not been done before in the literature. Detailed numerical studies on this new numerical scheme shows numerical convergence and good agreement with the large-deformation model. Dynamics of an axisymmetric viscous drop under an electric field is being simulated using this novel numerical code.

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 Dynamics of Deformation of Liquid Drops written by H. H. Chiu and published by . This book was released on 1969 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: A time dependent analysis is made of the deformation of an initially spherical drop moving in an unbound fluid at low Reynolds number. It is found that the excitation of a particular mode of deformation, including simple deformation, oscillation, and unstable deformation, depends on the Reynolds number, Weber number, the ratios of the two fluid densities and viscosities. The result of an analysis in the limit of vanishing voscosities shows that the droplet vibrates. The characteristic frequency obtained in the present analysis agrees with that previously obtained by H. Lamb. For large viscosities a limiting analysis indicates that a droplet deforms asymptotically to the equilibrium shape predicted by T.D. Taylor and A. Acrivos. The characteristic time of the deformation for ethyl alcohol droplets of 20 to 80 micrometers in diameter vary approximately from 0.001 sec to 0.005 sec. The effects of increasing temperature and pressure, free stream velocity and the droplet size are examined numerically for the deformation of ethyl alcohol drops. The unstable modes of deformation are likely to be excited at Reynolds number and Weber number both greater than unity. (Author).

Download or read book Numerical Simulation of Droplet deformation by a Level Set Approach with Surface Tension written by Roberto Croce and published by . This book was released on 2008 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Droplet Deformation Using Spectral Element Method written by Yu Zheng and published by . This book was released on 2007 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of the Droplet surface Impact Using InterFoam written by Fei Gao and published by . This book was released on 2015 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Droplet dynamics involves multi-scale forces from inertia body force, interior viscous shear stress to surface tension. The main purpose of this thesis is to simulate the normal impact of a liquid droplet on a hydrophobic surface by solving for the Navier-Stokes equations. The numerical results obtained is used to evaluate the effects of variable parameters on the droplet deformation evolution. The numerical simulation also works as a complimentary part of the experimental exploration, by the group members in the Droplet-Surface Impact Project in Northeastern University. The computational tool used is OpenFOAM, an open source CFD software package licensed and distributed by the OpenFOAM Foundation. The specific solver used is interFoam for this two phase problem. Water is modeled as a representative of the Newtonian fluids, while blood is modeled to represent non-Newtonian fluids. Multiple variables of the droplet-surface impact are investigated numerically: initial velocity, droplet diameter, transport properties, all of which contributes to a variation of the Weber number. The numerical results obtained for water droplets are supported by experimental data and also semi-empirical correlations. The spreading behavior and generation of ripples are in good agreement with that observed in the experimental tests. As the capillary effects become more dominant in the recoiling period, a discrepancy starts to show by a pre-maturely generated secondary droplet in simulation. Possible reasons are speculated for this discrepancy between numerical and experimental results. In the numerical comparison between water and blood droplets, a resemblance of droplet behavior in the initial spreading process is observed, while the recoiling process shows differences: blood droplets rebound in an "irregular" way compared to water droplets. The difference in deformation behaviors caused by varied transport properties leads to a way of distinguishing liquids by simple droplet-surface impact tests.

Download or read book A study of droplet deformation written by Hannah Fry and published by Lulu.com. This book was released on 2012-09-14 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: In both engineering and medical applications it is often useful to use the knowledge of the conditions under which adhering liquid droplets appear, deform and interact with surrounding fluids, in order to either remove or create them. Examples include the de-wetting of aircraft surfaces and the process of injecting glue into the bloodstream in the treatment of aneurysms. In this study, we look at various methods of modelling a particular class of droplets - those attached to a wall in the presence of an external shear flow.

Download or read book Numerical Modeling of Flow and Deformations Induced in a Droplet Subjected to Alternating Electric Field written by Nithin S. Panicker and published by . This book was released on 2012 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Numerical Simulation of Bubble and Droplet Deformation by a Level Set Approach with Surface Tension in Three Dimensions written by Roberto Croce and published by . This book was released on 2008 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Study of Drop Formation by a Vortex Ring written by Chiyoon Song and published by . This book was released on 2001 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Magnetic Fluids written by Elmars Blums and published by Walter de Gruyter. This book was released on 2010-10-13 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 Electrokinetic and Colloid Transport Phenomena written by Jacob H. Masliyah and published by John Wiley & Sons. This book was released on 2006-05-26 with total page 733 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new, definitive perspective of electrokinetic and colloid transport processes Responding to renewed interest in the subject of electrokinetics, Electrokinetic and Colloid Transport Phenomena is a timely overview of the latest research and applications in this field for both the beginner and the professional. An outgrowth of an earlier text (by coauthor Jacob Masliyah), this self-contained reference provides an up-to-date summary of the literature on electrokinetic and colloid transport phenomena as well as direct pedagogical insight into the development of the subject over the past several decades. A distinct departure from standard colloid science monographs, Electrokinetic and Colloid Transport Phenomena presents the most salient features of the theory in a simple and direct manner, allowing the book to serve as a stepping-stone for further learning and study. In addition, the book uniquely discusses numerical simulation of electrokinetic problems and demonstrates the use of commercial finite element software for solving these multiphysics problems. Among the topics covered are: * Mathematical preliminaries * Colloidal systems * Electrostatics and application of electrostatics * Electric double layer * Electroosmosis and streaming potential * Electrophoresis and sedimentation potential * London-Van der Waals forces and the DLVO theory * Coagulation and colloid deposition * Numerical simulation of electrokinetic phenomena * Applications of electrokinetic phenomena Because this thorough reference does not require advanced mathematical knowledge, it enables a graduate or a senior undergraduate student approaching the subject for the first time to easily interpret the theories. On the other hand, the application of relevant mathematical principles and the worked examples are extremely useful to established researchers and professionals involved in a wide range of areas, including electroosmosis, streaming potential, electrophoretic separations, industrial practices involving colloids and complex fluids, environmental remediation, suspensions, and microfluidic systems.