Author
Bernard Bunner
Bio: Bernard Bunner is an academic researcher from University of Michigan. The author has contributed to research in topics: Reynolds number & Bubble. The author has an hindex of 8, co-authored 18 publications receiving 2453 citations.
Papers
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TL;DR: In this paper, a front-tracking method for multiphase flows is presented, which is based on writing one set of governing equations for the whole computational domain and treating the different phases as one fluid with variable material properties.
2,011 citations
TL;DR: In this article, a simulation of the motion of up to 216 3D buoyant bubbles in periodic domains is presented, where the full Navier-Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension.
Abstract: Direct numerical simulations of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains are presented. The full Navier–Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds number is about 12–30, depending on the void fraction; deformations of the bubbles are small. Although the motion of the individual bubbles is unsteady, the simulations are carried out for a sufficient time that the average behaviour of the system is well defined. Simulations with different numbers of bubbles are used to explore the dependence of the statistical quantities on the size of the system. Examination of the microstructure of the bubbles reveals that the bubbles are dispersed approximately homogeneously through the flow field and that pairs of bubbles tend to align horizontally. The dependence of the statistical properties of the flow on the void fraction is analysed. The dispersion of the bubbles and the fluctuation characteristics, or ‘pseudo-turbulence’, of the liquid phase are examined in Part 2.
208 citations
TL;DR: In this article, the full Navier-Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension.
Abstract: Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented The full Navier–Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension The Eotvos number is taken as equal to 5, so that the bubbles are ellipsoidal, and the Galileo number is 900, so that the rise Reynolds number of a single bubble in an unbounded flow is about 26 Three values of the void fraction have been investigated: 2%, 6% and 12% At 6%, a change in the behaviour of the bubbles is observed The bubbles are initially dispersed homogeneously throughout the flow field and their average rise Reynolds number is 23 After the bubbles have risen by about 90 bubble diameters, they form a vertical stream and accelerate The microstructure of the bubble suspension is analysed and an explanation is proposed for the formation of these streams The results for the ellipsoidal bubbles are compared to the results for nearly spherical bubbles, for which the Eotvos number is 1 and the Galileo number is 900 The dispersion of the bubbles and the velocity fluctuations in the liquid phase are analysed
190 citations
TL;DR: In this article, a simulation of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains is presented, and it is shown that the turbulent kinetic energy increases with void fraction and scales with the void fraction multiplied by the square of the average rise velocity of the bubbles.
Abstract: Direct numerical simulations of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains are presented. The bubbles are nearly spherical and have a rise Reynolds number of about 20. The void fraction ranges from 2% to 24%. Part 1 analysed the rise velocity and the microstructure of the bubbles. This paper examines the fluctuation velocities and the dispersion of the bubbles and the ‘pseudo-turbulence’ of the liquid phase induced by the motion of the bubbles. It is found that the turbulent kinetic energy increases with void fraction and scales with the void fraction multiplied by the square of the average rise velocity of the bubbles. The vertical Reynolds stress is greater than the horizontal Reynolds stress, but the anisotropy decreases when the void fraction increases. The kinetic energy spectrum follows a power law with a slope of approximately 3:6 at high wavenumbers.
117 citations
TL;DR: In this article, the Navier-Stokes equation is solved by a front tracking/finite difference method that allows a fully deformable interface, and the evolution of 91 nearly spherical bubbles at a void fraction of 6% is followed as the bubbles rise over 100 bubble diameters.
Abstract: Direct numerical simulations of the motion of many buoyant bubbles are presented. The Navier–Stokes equation is solved by a front tracking/finite difference method that allows a fully deformable interface. The evolution of 91 nearly spherical bubbles at a void fraction of 6% is followed as the bubbles rise over 100 bubble diameters. While the individual bubble velocities fluctuate, the average motion reaches a statistical steady state with a rise Reynolds number of about 25.
91 citations
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TL;DR: In this paper, a front-tracking method for multiphase flows is presented, which is based on writing one set of governing equations for the whole computational domain and treating the different phases as one fluid with variable material properties.
2,011 citations
TL;DR: A review of the fundamental and technological aspects of these subjects can be found in this article, where the focus is mainly on surface tension effects, which result from the cohesive properties of liquids Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science.
Abstract: Jets, ie collimated streams of matter, occur from the microscale up to the large-scale structure of the universe Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology They also arise from the last but one topology change of liquid masses bursting into sprays Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects
1,583 citations
Book•
01 Dec 1988
TL;DR: In this paper, the basic processes in Atomization are discussed, and the drop size distributions of sprays are discussed.Preface 1.General Considerations 2.Basic Processes of Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.AtOMizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index
Abstract: Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index
1,214 citations
TL;DR: A new numerical method for improving the mass conservation properties of the level set method when the interface is passively advected in a flow field that compares favorably with volume of fluid methods in the conservation of mass and purely Lagrangian schemes for interface resolution.
1,120 citations
University of Minnesota1, University of Michigan2, Florida State University3, University of Twente4, Queen's University Belfast5, University of California, Berkeley6, University of Belgrade7, University of Bristol8, University of Padua9, University of York10, Osaka University11, Loughborough University12, Leibniz Association13, Brno University of Technology14, Academy of Sciences of the Czech Republic15, Comenius University in Bratislava16, École Polytechnique17, Ulster University18, Clarkson University19, Michigan Technological University20, University of Antwerp21, Lublin University of Technology22, University of Montpellier23, Eindhoven University of Technology24, Max Planck Society25, University of Alberta26, Durham University27, Lawrence Berkeley National Laboratory28, National Institute of Advanced Industrial Science and Technology29, Saint Petersburg State University30
TL;DR: A review of the state-of-the-art of this multidisciplinary area and identifying the key research challenges is provided in this paper, where the developments in diagnostics, modeling and further extensions of cross section and reaction rate databases are discussed.
Abstract: Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas.
1,078 citations