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Drop Deformation (drop + deformation)
Selected AbstractsDrop Deformation and Breakup Mechanisms in Viscoelastic Model Fluid Systems and Polymer BlendsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Frej Mighri Abstract This paper reviews the dispersion mechanisms in viscoelastic systems under relatively high shear rate conditions. In particular, two non-Newtonian deformation and breakup mechanisms were revealed by flow visualization in a transparent Couette shearing setup. The first one is the dispersed droplet elongation perpendicular to the flow direction. This was observed only for viscoelastic drops and had been associated to normal force buildup in the droplet. The second deformation/breakup mechanism was observed in very high viscosity ratio polymer systems. It consists in erosion at the drop surface. Clouds of very small ribbons and sheets were developed around the drop then stretched and finally broken into very small droplets, rapidly distributed in the matrix. Cet article examine les mécanismes de dispersion dans les mélanges viscoélastiques à des taux de cisaillement relativement élevés. Deux nouveaux mécanismes de déformation et de rupture de gouttes viscoélastiques ont été révélés en utilisant un montage de visualisation transparent de type Couette. Le premier mécanisme est l'orientation de l'axe principal de la goutte perpendiculairement à la direction de l'écoulement, phénomène qui n'a été observé que pour des gouttes viscoélastiques. Ce phénomène a été relié au développement de forces normales (élasticité) à l'intérieur de la goutte. Le second mécanisme de déformation/rupture a été observé avec des systèmes de polymères fondus possédant des rapports de viscosité élevés. Il consistait en une érosion de la surface de la goutte générant ainsi un nuage de gouttelettes et de minces feuillets autour de la goutte principale. Ces derniers s'étiraient suite à l'écoulement de la matrice et finissaient par être brisés en gouttelettes très fines rapidement dispersées dans la matrice. [source] Numerical simulation of drop deformation and breakup in shear flowHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2007Lin Chang-Zhi Abstract Three-dimensional numerical simulation of the deformation and breakup of an isolated liquid drop suspended in immiscible viscous fluid under shear flow was performed with diffuse interface method. The governing equations of the model were described by Navier, Stokes, Cahn, Hilliard equations. The surface tension was treated as a modified stress. In this paper, a uniform staggered Cartesian grid was used. The transient Navier, Stokes equations were solved by an approximation projection method based on pressure increment formulation, while the Cahn, Hilliard equations were solved by a nonlinear full approximation multigrid method. The numerical results of the drop deformation and breakup were in good agreement with the experimental measurements. Therefore, the present model could be perfectly applied to study the mechanism of drop deformation and breakup. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 286, 294, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20160 [source] Numerical analysis of deformed free surface under AC magnetic fieldsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2004Haruhiko Kohno Abstract A novel numerical scheme for the analysis of large deformation of electrically conducting liquid under alternating current magnetic fields is presented. The main features are characterized by two numerical tools; the level set method to calculate deformed free surface stably and the hybrid finite element method and boundary element method to discretize the electromagnetic field efficiently. Two-dimensional numerical simulation of conducting drop deformation is carried out to demonstrate the effectiveness of the present scheme, and the oscillatory behaviour, which depends on the magnitude of surface tension and Lorentz force, is investigated. Copyright © 2004 John Wiley & Sons, Ltd. [source] A comparison of boundary element and finite element methods for modeling axisymmetric polymeric drop deformationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2001Russell Hooper Abstract A modified boundary element method (BEM) and the DEVSS-G finite element method (FEM) are applied to model the deformation of a polymeric drop suspended in another fluid subjected to start-up uniaxial extensional flow. The effects of viscoelasticity, via the Oldroyd-B differential model, are considered for the drop phase using both FEM and BEM and for both the drop and matrix phases using FEM. Where possible, results are compared with the linear deformation theory. Consistent predictions are obtained among the BEM, FEM, and linear theory for purely Newtonian systems and between FEM and linear theory for fully viscoelastic systems. FEM and BEM predictions for viscoelastic drops in a Newtonian matrix agree very well at short times but differ at longer times, with worst agreement occurring as critical flow strength is approached. This suggests that the dominant computational advantages held by the BEM over the FEM for this and similar problems may diminish or even disappear when the issue of accuracy is appropriately considered. Fully viscoelastic problems, which are only feasible using the FEM formulation, shed new insight on the role of viscoelasticity of the matrix fluid in drop deformation. Copyright © 2001 John Wiley & Sons, Ltd. [source] The effect of surfactants on deformation of falling non-Newtonian drops in a Newtonian liquidTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2008Denis RodrigueArticle first published online: 4 MAR 200 Abstract Deformation of settling non-Newtonian ellipsoidal drops in a Newtonian liquid was experimentally observed. Corn oil was used as the Newtonian phase and solutions of polyacrylamide in aqueous glycerine as the non-Newtonian phase. The shear-thinning behaviour of the drops fluid was controlled by the amount of polymer dissolved, while the effect of interfacial tension was examined using different concentrations of sodium dodecyl sulphate (SDS). In the range of 1,<,E,<,2.9, 0.2,<,Eo,,<,23, and 0,<,Ma,<,17.2, drop eccentricity increased linearly with a modified Eötvös number taking into account the effect of surfactants. For the range of experimental conditions tested, drop deformation was mainly controlled by viscous and interfacial tension forces, while shear-thinning and inertia effects were negligible. On a observé expérimentalement la déformation de gouttelettes ellipsödales non newtoniennes sédimentant dans un liquide newtonien. Del'huile de mäs a été utilisée comme phase newtonienne et des solutions de polyacrylamide dans de la glycérine aqueuse comme phase non newtonienne. Le comportement rhéofluidifant du fluide des gouttes est contrôlé par la quantité de polymères dissous, tandis que l'effet de la tension interfaciale est examiné avec différentes concentrations de sulfate de dodécyle de sodium. Dans la gamme de 1,<,E,<,2,9, 0,2,<,Eo 23 and 0,<,Ma,<,17,2, l'eccentricité des gouttelettes augmente linéairement avec le nombre d'Eötvös modifié en tenant compte de l'effet des surfactants. Pour la gamme des conditions expérimentales testées, la déformation des gouttelettes est principalement contrôlée par les forces de tension visqueuse et interfaciale, tandis que les effets de rhéofluidifiance et d'inertie sont négligeables. [source] | ||||||||||