Download or read book Effect of Velocity and Gravity on Bubble Dynamics written by Sandipan Maity and published by . This book was released on 2000 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interacting Effects of Inertia and Gravity on Bubble Dynamics written by Yohann Lilian Rousselet and published by . This book was released on 2014 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: Knowledge of the physical mechanisms governing bubble dynamics and two-phase heat transfer is critical in order to accurately predict and scale the performance of two-phase systems, most importantly in low-g environments. To better understand flow boiling, especially under microgravity conditions, the dynamics of single and multiple bubbles under different levels of bulk liquid velocity, surface orientation, contact angle, and substrate materials are studied in this work. Microfabricated cavities at the center of a flat heating surface are used to generate bubbles. Silicon and aluminum are used as substrate materials, with contact angles of 56° and 19°, respectively, with water as test liquid. The investigated bulk liquid velocities ranged from 0 m/s to 0.25 m/s, while surface orientation varies from horizontal to vertical, through 30°, 45° and 60°, and cavity spacing from 0.4 mm to 1.2 mm, in upflow conditions. Bulk liquid temperature was set close to saturation temperature, with bulk liquid subcooling less than 1° C, and wall superheat was maintained between 5.0° C and 6.0 °C. Based on the experimental data, a simple force balance model was developed, and is used to develop a model to predict bubble lift off. These forces are the lift force (F_b), the buoyancy force (F_b), the surface tension force (F_s), the contact pressure force (F_cp), and the inertia of both the vapor and the liquid displaced by the growing bubble. It is showed that at the instant when bubble lift off is initiated, the sum of forces acting on the bubble is equal to zero (and then becomes positive in the direction normal to the heater). This force balance is used to develop an expression for bubble lift off diameter. It also is found that for single and merged bubbles, when lift off occurs, buoyancy and lift forces are the only forces acting on the bubble, regardless of orientation, contact angle and flow velocity, and that for all cases, the ratio (F_b + F1) / A1 is constant and equal to 2.25 N/m2, where A1 is the bubble surface area at lift off.
Download or read book The Motion of Bubbles and Drops in Reduced Gravity written by R. Shankar Subramanian and published by Cambridge University Press. This book was released on 2001-04-09 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 2001 book provides a thorough review of the motion of bubbles and drops in reduced gravity.
Download or read book Experimental Investigation of Nucleate Boiling Bubble Dynamics in Normal and Zero Gravities written by Thomas H. Cochran and published by . This book was released on 1968 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Bubble Dynamics and Shock Waves written by Can F. Delale and published by Springer Science & Business Media. This book was released on 2012-10-08 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the interplay of bubble dynamics and shock waves, covering shock wave emission by laser generated bubbles, pulsating bubbles near boundaries, interaction of shock waves with bubble clouds, applications in shock wave lithotripsy, and more.
Download or read book Effect of Gravity and Liquid Subcooling on Bubble Dynamics written by Satjeet Singh and published by . This book was released on 1999 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubble Dynamics in Stagnation Flow written by John E. Starrett and published by . This book was released on 1982 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubble Dynamics and Forced Convection Boiling Heat Transfer with Low Velocity written by Longhu Li and published by . This book was released on 1993 with total page 866 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubble and Particle Dynamics in Acoustic Fields written by and published by . This book was released on 2005 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Dynamics of a Bubble Rising in an Inclined Channel written by Kevin Mitchell DeBisschop and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A bubble rising between two inclined parallel walls is investigated numerically. Stokes flow is assumed and we use the boundary integral method to solve the problem. This is a numerical method which reduces the moving boundary problem to a system of integral equations that can be discretized and marched forward in time. Computations are done for channels inclined at various angles, different flow rates, and for different physical parameters. Our computations allow us to determine the time dependent evolution of the bubble and to predict the existence of steady state solutions. We find that the bubbles can either detach a smaller bubble, be unsteady, or approach a steady state. From the steady states a variety of physical parameters can be determined, e.g. bubble rise velocity. The results are compared with existing experimental data. The effect of surfactants on the shapes of bubbles is also investigated. Surfactants are found to streamline the bubbles and increase their speeds. Analogous inviscid problems are also studied. We first study a bubble that is in a flow that is next to a wall. There is no gravity present and we find that moving closer to the wall can cause the bubble center to deform and rupture. Finally we consider a model for bubble motion near a wall which includes both gravitational and viscous effects. We find that steady states can exist only at certain distances from the wall.
Download or read book Micro bubble Dynamics in Turbulent Flow written by Zhentong Zhang (docteur en mécanique des fluides).) and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is devoted to the study of the motion of small bubbles in homogeneous isotropic turbulent flows. The work addresses several questions related to the statistical description of the hydrodynamic forces exerted on a bubble as well as the stochastic modeling of their high frequency fluctuations. First, we propose a model for the acceleration of micro-bubbles (smaller than the dissipative scale of the flow) subjected to the drag and the fluid inertia forces. This model, that depends on the Stokes number, the Reynolds number and the density ratio, reproduces the evolution of the acceleration variance as well as the relative importance and alignment of the two forces as observed from Direct Numerical Simulations (DNS). Second, based on the observation that acceleration statistics conditional to the local kinetic energy dissipation rate are invariant with the Stokes number and the dissipation rate, we propose a stochastic model for the instantaneous bubble acceleration vector accounting for the small-scale intermittency of the turbulent flows. The norm of the bubble acceleration is obtained by modeling the dissipation rate along the bubble trajectory from a log-normal stochastic process, whereas its orientation is given by two coupled random walk on a unit sphere in order to model the evolution of the joint orientation of the drag and inertia forces acting on the bubble. Furthermore, the proposed stochastic model for the bubble acceleration is used in the context of large eddy simulations (LES) of turbulent flows laden with small bubbles. It can effectively reproduce effect of turbulent motion at scales smaller than the mesh resolution by adding a random contribution depending on local average dissipation rate. Comparisons with DNS and standard LES, show that the proposed model improves significantly the statistics of the bubbly phase. Third, we extend the previous results in the case of bubbles with large Reynolds number by considering non-linear drag laws. We define an effective relaxation time based on the drag coefficient to characterize bubble motion (acceleration,velocity). Eventually we study the effect of buoyancy and lift force on the bubble dynamics, and analyze the reduction of the average rising velocity in turbulent flow compared to quiescent flows. It is observed that bubbles preferentially explore region having downward fluid acceleration which contributes through the inertia force to reduction of the rising velocity. In addition, as already observed, the lift force brings preferably bubbles into downstream fluid motion which also reduce their rising velocity.
Download or read book Bubble Wake Dynamics in Liquids and Liquid Solid Suspensions written by Liang-Shih Fan and published by Butterworth-Heinemann. This book was released on 1990-08-21 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to a fundamental understanding of the fluid dynamic nature of a bubble wake, more specifically the primary wake, in liquids and liquid-solid suspensions, an dto the role it plays in various important flow phenomena of multiphase systems. Examples of these phenomena are liquid/solids mixing, bubble coalescence and disintergration, particle entrainment to the freeboard, and bed contraction.
Download or read book Principles and Applications in Nuclear Engineering written by Rehab Abdel Rahman and published by BoD – Books on Demand. This book was released on 2018-09-19 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear engineering could be viewed as the engineering field that ensures optimum and sustainable technological applications of natural and induced radioactive materials in different industrial sectors. This book presents some advanced applications in radiation effects, thermal hydraulics, and radionuclide migration in the environment. These scientific contributions from esteemed experts introduce some nuclear safety principals, current knowledge about radiation types, sources and applications, thermal properties of heat transfer media, and the role of sorption in retarding radionuclide migration in the environment. This book also covers the advances in identifying radiation effects in dense gas-metal systems, application of dense granular materials as high power targets in accelerator driven systems and irradiation facilities, evaluation of boiling heat transfer in narrow channels, and application of fluorescence quenching techniques to monitor uranium migration.
Download or read book What We Learned from Cavitation Bubbles in Microgravity written by Mohamed Farhat and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present chapter is about the Flash and Splash project, which is dedicated to the study of bubble dynamics in microgravity. The story of this project started in 2004 with a simple curiosity on how a cavitation bubble may behave within a water drop and evolved into an outstanding, internationally renowned science project as well as a wonderful human adventure. So far, we have participated in nine European Space Agency (ESA) parabolic flight campaigns (PFC) and made a significant progress in understanding the cavitation phenomenon. First, we investigated the dynamics of a cavitation bubble within a water drop and learned how the collapse may lead to the formation of a double jet. We discovered the formation of secondary cavitation due to the confinement of shockwaves within the drop. We used this result to propose a new path for erosion due to a high-speed impact of water drops on a solid surface. Then, we addressed the effect of gravity on bubble dynamics and came up with a unified framework to explain and predict key phenomena, such as microjets, shockwaves and luminescence. Parabolic flights gave us the unique opportunity to modulate the gravity-induced pressure gradient, which is crucial for the fate of a collapsing bubble.
Download or read book Bubble Dynamics Research Theory Instrumentation Results written by Frederick G. Hammitt and published by . This book was released on 1972 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Assessments on Bubble Dynamics Applied to Flotation Cells written by Asif Mammadov and published by . This book was released on 2016 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Au, Ag, Hg, many other metals, diamond, coal, oil and tar sands are extracted by flotation process. We can define flotation as a single, most significant unit operation in mineral processing, used in extraction of all kinds of minerals. A study of air bubble dynamics and gas-liquid multiphase flow is important for the design, development and understanding of industrial processes such as bubble column reactors, flotation cells and boilers. Hence bubble generation and attachment is an important part of flotation process. In order to understand bubble dynamics, we built models of single bubble systems. The growth and detachment of air bubble from single orifice in water tank was studied. An axisymmetric model based on the Volume of Fluid method, available in ANSYS-Fluent software was used for simulation of air bubble rising in water. Numerous numerical simulations were carried out using an axisymmetric domain with different orifice diameters (0.8, 0.4 mm), air inlet velocities (50, 150 mlph) and phase surface tensions (50, 72 mN/m). Bubble growth and rise velocity were studied and validated against experimental data published in literature. Relative good agreement was achieved. Velocity profiles of the rising bubbles as well as Reynolds, Weber and Capillary numbers were calculated. Effect of surface tension and nozzle diameter to bubble size and dynamics were discussed. It was shown that smaller surface tension of the system yields to smaller bubble size which is more favorable for flotation process.
