Download or read book On the Effect of Turbulence on Bubbles written by Marcus Johannes Wilhelmus Harleman and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Bubbles on Developed Turbulence written by Thomas Hendrik van den Berg and published by . This book was released on 2006 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Bubbles on Turbulence in a Confined Water Jet written by Sanjay Kumar and published by . This book was released on 1988 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Gravity on Sheared Turbulence Laden With Bubbles Or Droplets written by and published by . This book was released on 2004 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report studies the dynamics of particle-laden turbulent flows. Specifically, it addresses the effect of the turbulence on the concentration field and drift velocity of spherical particles. The coupling between the particle accumulation and the modification of the drift velocity is also investigated. Turbulent flows with and without mean shear are analyzed and the effect of the turbulent length scales on the behavior of the particles is described. The effect of the density ratio between the disperse and the continuous phase was considered in the two extreme cases of water droplets in air (1000) and air bubbles in water (1/1000).
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 The Effect of Turbulence on the Concentration and Velocity Fields of Microparticles written by Alberto Aliseda and published by . This book was released on 2004 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Splitting and Dispersion of Bubbles by Turbulence written by Carlos Martinez Sarasola and published by . This book was released on 1998 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Modeling Bubble induced Turbulence Effects in Gas liquid Flows Using Time averaged Equations written by Aytekin Gel and published by . This book was released on 1994 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubbly Flows written by Martin Sommerfeld and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book summarises the outcom of a priority research programme: 'Analysis, Modelling and Computation of Multiphase Flows'. The results of 24 individual research projects are presented. The main objective of the research programme was to provide a better understanding of the physical basis for multiphase gas-liquid flows as they are found in numerous chemical and biochemical reactors. The research comprises steady and unsteady multiphase flows in three frequently found reactor configurations, namely bubble columns without interiors, airlift loop reactors, and aerated stirred vessels. For this purpose new and improved measurement techniques were developed. From the resulting knowledge and data, new and refined models for describing the underlying physical processes were developed, which were used for the establishment and improvement of analytic as well as numerical methods for predicting multiphase reactors. Thereby, the development, lay-out and scale-up of such processes should be possible on a more reliable basis.
Download or read book Effects of Free stream Turbulence Intensity on Laminar Separation Bubbles written by Mark Istvan and published by . This book was released on 2017 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil are studied experimentally in a wind tunnel facility. A parametric study is performed over a range of chord Reynolds numbers from 100 000 to 200 000, angles of attack from 0 to 20, and free-stream turbulence intensities from 0.09% to 2.03% in order to unravel the effects of each parameter on suction side laminar separation bubble topology and the resulting changes in airfoil lift. In order to investigate the effects of free-stream turbulence intensity on the streamwise and spanwise flow development within a separation bubble, flow field measurements are made using planar Particle Image Velocimetry for an angle of attack of 4, chord Reynolds numbers of 80 000 and 125 000, and free-stream turbulence intensities between 0.10% and 1.94%. The results show that increasing the level of free-stream turbulence intensity leads to a reduction in the length of the separation bubble formed over the suction side of the airfoil. The reduction in bubble length is a result of a downstream shift in mean separation as well as an upstream shift in mean transition and, consequently, mean reattachment. At low angles of attack, the reduction in separation bubble length leads to a slight reduction in airfoil lift, while at pre-stall angles of attack the reduction in separation bubble length alleviates the loss of suction at the location of the suction peak, thereby increasing lift, and can delay stall. While the effects of turbulence intensity and chord Reynolds number on the mean flow are shown to be similar, their effects on transition are shown to be notably different. The upstream shift in mean transition with increasing turbulence intensity is shown to be the result of disturbances reaching higher amplitudes earlier upstream as the level of turbulence intensity is increased, despite increased bubble stability. This result suggests that the increased initial perturbation amplitude at elevated turbulence intensity levels is solely responsible for the upstream shift in mean transition. In contrast, the upstream shift in mean transition with increasing Reynolds number is a result of decreased bubble stability. Wavenumber-frequency spectra of velocity fluctuations in the separated shear layer show that disturbances become more broadband in both time and space with increasing turbulence intensity. In addition, the results show that as the level of free-stream turbulence intensity is increased, the spanwise coherence of shear layer rollers decreases at the location of roll-up, leading to earlier vortex breakdown. At elevated levels of turbulence intensity, streamwise streaks of low speed fluid are observed, and originate in the boundary layer upstream of the separation bubble. These streaks form as a result of the onset of bypass transition, leading to significant changes in bubble dynamics, particularly at the highest level of turbulence intensity investigated. The results suggest that the transition mechanism in the separation bubble at the highest level of turbulence intensity investigated is altered.
Download or read book Viscous Drag Reduction in Boundary Layers written by and published by AIAA. This book was released on 1990 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluid Flow Phenomena written by Paolo Orlandi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the simulation of the incompressible Navier-Stokes equations for laminar and turbulent flows. The book is limited to explaining and employing the finite difference method. It furnishes a large number of source codes which permit to play with the Navier-Stokes equations and to understand the complex physics related to fluid mechanics. Numerical simulations are useful tools to understand the complexity of the flows, which often is difficult to derive from laboratory experiments. This book, then, can be very useful to scholars doing laboratory experiments, since they often do not have extra time to study the large variety of numerical methods; furthermore they cannot spend more time in transferring one of the methods into a computer language. By means of numerical simulations, for example, insights into the vorticity field can be obtained which are difficult to obtain by measurements. This book can be used by graduate as well as undergraduate students while reading books on theoretical fluid mechanics; it teaches how to simulate the dynamics of flow fields on personal computers. This will provide a better way of understanding the theory. Two chapters on Large Eddy Simulations have been included, since this is a methodology that in the near future will allow more universal turbulence models for practical applications. The direct simulation of the Navier-Stokes equations (DNS) is simple by finite-differences, that are satisfactory to reproduce the dynamics of turbulent flows. A large part of the book is devoted to the study of homogeneous and wall turbulent flows. In the second chapter the elementary concept of finite difference is given to solve parabolic and elliptical partial differential equations. In successive chapters the 1D, 2D, and 3D Navier-Stokes equations are solved in Cartesian and cylindrical coordinates. Finally, Large Eddy Simulations are performed to check the importance of the subgrid scale models. Results for turbulent and laminar flows are discussed, with particular emphasis on vortex dynamics. This volume will be of interest to graduate students and researchers wanting to compare experiments and numerical simulations, and to workers in the mechanical and aeronautic industries.
Download or read book Turbulence and Interactions written by Michel Deville and published by Springer Science & Business Media. This book was released on 2009-03-20 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains seven keynote lectures of the TI 2006 conference that was held in Porquerolles, May 29-June 2, 2006. This book offers a view on theory, experiments and numerical simulations in the field of turbulence.
Download or read book Effect of Freestream Turbulence on Laminar Separation Bubbles and Flow Transition on a Low Reynolds Number Airfoil written by Jacob Zilli and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of freestream turbulence intensity on the laminar separation bubble and flow transition over an SD7003 airfoil was investigated. Measurements were performed for Reynolds numbers ranging from 60,000 to 250,000, various angles of attack and turbulence intensities between 0.05% and 0.99%. Boundary layers with a separation bubble were found to develop a turbulent boundary layer more rapidly than those without. The trends in the skin friction downstream of the peak corresponding to the development of a turbulent boundary layer were very similar for all turbulence intensities, suggesting the turbulent boundary layer forming downstream of transition was not significantly affected by the turbulence intensities investigated. The fluctuating velocity spectra showed that the increase in freestream turbulence intensity introduced sufficient energy to the laminar boundary layer to initiate transition before the flow was able to separate at an angle of attack of 4â Ś but not at 8â Ś.
Download or read book Free stream Turbulence Effects on Laminar Separation Bubbles at Low Reynolds Numbers written by Blago Hristovski and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 2013-10-22 with total page 380 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.
