Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session G2: Suspensions: General |
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Chair: Elisabeth Guazzelli, Aix-Marseille University, CNRS Room: 3002 |
Monday, November 24, 2014 8:00AM - 8:13AM |
G2.00001: Geometrically-protected reversibility in hydrodynamic Loschmidt-echo experiments Raphael Jeanneret, Joost Weijs, Denis Bartolo We demonstrate an archetypal Loschmidt-echo experiment where thousands of droplets interact in a reversible fashion via a viscous fluid. Firstly, we show that, unlike equilibrium systems, periodically driven microfluidic emulsions self-organize and geometrically protect their macroscopic reversibility. This self-organization is not merely dynamical, it has a clear structural signature akin to the one found in a mixture of molecular liquids. Secondly, we evidence that above a maximal shaking amplitude both structural order and reversibility are lost simultaneously in the form of a 1st order non-equilibrium phase transition. Thirdly, we account for this discontinuous transition, in term of a memory-loss process. [Preview Abstract] |
Monday, November 24, 2014 8:13AM - 8:26AM |
G2.00002: Colloidal deposition and aggregation in the presence of charged collectors Behnam Sadri, Arvind Rajendran, Subir Bhattacharjee The transport of colloidal particles in porous media is of great importance in sub-surface environments. These colloidal particles facilitate transport of contaminants, low-soluble compounds and metals in groundwater. Here, we have studied transport dynamics of colloids inside porous medium using a combination of column experiments and batch studies. Polystyrene latex beads (100nm), as colloidal agents, and soda lime glass beads, as porous medium, are employed in this work. On the one hand, batch experiments are undertaken to better understand concurrent aggregation and deposition of particles. On the other hand, column experiments are performed to understand the flow induced deposition of colloidal particles in the interstitial voids. Effect of collector surface preparation, pH, colloidal suspension concentration and collector beads mass is studied. Chemical release and shear field are revealed as two significant factors lying behind the coagulation of colloidal particles. These findings help us to better distinguish mechanisms responsible for the transport of colloids inside porous medium. [Preview Abstract] |
Monday, November 24, 2014 8:26AM - 8:39AM |
G2.00003: The role of short-ranged and long-ranged hydrodynamic interactions on aggregation of colloidal particle in colloid-polymer mixtures Arman Boromand, Safa Jamali, Joao Maia Colloidal Gels i.e. disordered arrested systems has been studied extensively during the past decades both experimentally and computationally. Despite their widespread applications in various industries e.g. cosmetic, food, their physical principals are still far beyond being understood. The interplay between different types of interactions e.g. quantum scale, short-ranged, and long-ranged turned dynamics and thermodynamics of the colloidal systems to one the most intriguing areas in Physics. Many authors have implemented different simulation techniques such as molecular dynamics (MD) and Brownian dynamics (BD) to capture better picture during phase separation in colloidal system with short-ranged attractive force e.g. colloid-polymer mixtures. However, BD neglects multi-body hydrodynamic interactions (HI) and MD is limited considering the time and length scale of gel formation and long-time dynamics. In this presentation we used Core-modified dissipative particle dynamics (CM-DPD) with modified depletion potential, as a coarse-grain model, to address the gel formation process in short ranged-attractive colloidal systems. Due to the possibility to study short- and long-ranged HI separately in this method we studied the effect of each of those interactions on the final morphology and report on one of the controversial question in this field. In the second part of the presentation, we include colloidal-polymer interactions to extend/modify the Asakura-Oosawa potential model to semi-dilute region of polymer solution. [Preview Abstract] |
Monday, November 24, 2014 8:39AM - 8:52AM |
G2.00004: Flow-structure interaction of falling cones in unbounded flow media Dan Troolin, Lai Wing, Yaqing Jin, A.H. Hamed, Carlo Zuniga Zamalloa, Leonardo P. Chamorro The kinematics of falling objects in a fluid media at rest are dominated by the vorticity dynamics generated in the vicinity of the object. At a critical Reynolds number, the large-scale vortical structures shed by the body lose their axisymmetric character leading to unsteady lift and, consequently, body rotation. The dynamics of these motions depend on the body shape and can range from simple oscillatory motions to chaotic behavior. In this study, 2D and 3D Particle Image Velocimetry (PIV) are used to characterize the turbulence in the vicinity of cones of various shapes (aspect ratios) falling in a fluid media at complete rest. Translations and rotations experienced by the cones are tracked with a miniature and highly sensitive 3-axis accelerometer and 3-axis gyroscope inserted in the object. Coupling between vortex dynamics and body motions is characterized at various Reynolds numbers and cone shapes. [Preview Abstract] |
Monday, November 24, 2014 8:52AM - 9:05AM |
G2.00005: Effects of Hydrodynamic Interaction in Aerosol Particle Settling: Mesoscopic Particle-level Full Dynamics Simulations Shuiqing Li, Mengmeng Yang, Jeffrey Marshall A new mesoscopic particle-level approach is developed for the full dynamics simulation (FDS) of the settling of systems of aerosol micro-particles. The approach efficiently combines an adhesive discrete-element method for particle motions and an Oseen dynamics method for hydrodynamic interactions. Compared to conventional Stokeslet and Oseenlet simulations, the FDS not only accounts for the cloud-scale fluid inertia effect and the particle inertia effect, but also overcomes the singularity problem using a soft-sphere model of adhesive contact. The effect of hydrodynamic interactions is investigated based on FDS results. The particle inertia is found to reduce the mobility of particle clouds and to elongate the cloud on vertical direction. Meanwhile, the fluid inertia decreases the settling velocity by weakening the hydrodynamic interaction and tends to flatten the cloud, leading to breakup. Expressions for the settling velocity of particle cloud are proposed with consideration of fluid inertia effect and the cloud shape. Finally, the transformation in settling behavior from a finite particle cloud to an unbounded uniform suspension is explained. [Preview Abstract] |
Monday, November 24, 2014 9:05AM - 9:18AM |
G2.00006: Effect of roughness in periodically sheared clouds of particles Phong Pham, Bloen Metzger, Jason Butler We investigate experimentally the evolution of small clouds of non-Brownian particles submitted to a periodic shear under low Reynolds number conditions. The particle motion is irreversible during the first cycle. Beyond that, the particle motion is reversible. We find that the amount of irreversibility increases as the particle roughness is increased. An accurate prediction of the particles' trajectories is obtained with a minimal model including normal lubrication and a frictionless contact force. These experiments provide evidence that, in viscous flows, contacts between particles occur and strongly influence the particle dynamics. [Preview Abstract] |
Monday, November 24, 2014 9:18AM - 9:31AM |
G2.00007: Mixing at low Reynolds number by shearing suspensions Mathieu Souzy, Bloen Metzger, Cherifa Abid, Emmanuel Villermaux, Xiaolong Yin Sheared suspensions provide a unique system where mixing spontaneously occurs even under low Reynolds numbers conditions. Under flow, particles within the fluid experience frequent collisions with one another, and are thus deviated from their laminar streamlines. Particles can be thought of as many ``stirrers'' inducing disturbances in the fluid phase, which produce an efficient mixing. Using index matching and laser induced fluorescence, we investigate experimentally the evolution of the concentration profiles of a layer of dye initially applied on the outer wall of a cylindrical Couette cell, in a sheared suspension of neutrally buoyant, non-Brownian particles. Close to the walls, although the particle-translational-diffusive motion is frustrated, particle rotation significantly enhances the rate of mass transfer, which is found to propagate across the gap super-diffusively. The fine-scale mixing properties of this disordered flow are investigated as well. The stretching laws of isolated scalar blobs are measured and used to infer the probability density function of the concentration in the medium. [Preview Abstract] |
Monday, November 24, 2014 9:31AM - 9:44AM |
G2.00008: Dynamics of shear-induced migration of spherical particles in pipe flow Elisabeth Guazzelli, Braden Snook, Jason Butler We study the large-oscillation flow of a concentrated suspension in a pipe. Particle volume fraction and particle velocity are examined through refractive index matching techniques. The particles are seen to migrate toward the center of the pipe, i.e. from the region of high to low shear-rate. The dynamics of the shear-induced migration process is analyzed and in particular compared to the prediction of the suspension balance model using realistic rheological laws. [Preview Abstract] |
Monday, November 24, 2014 9:44AM - 9:57AM |
G2.00009: Inertial migration of spherical particles in square channel flows Kazuma Miura, Tomoaki Itano, Masako Sugihara-Seki It has been known that particles suspended in the laminar pipe flow migrate laterally toward a certain radial position due to the inertial effect. In this research, we investigated experimentally the inertial migration of neutrally buoyant spherical particles in square channel flows in the range of Reynolds numbers (Re) from 100 to 1200. The measurement of the particle positions at several cross-sections revealed that there are eight equilibrium positions of the particles in the cross-section, four of them located near the centers of the channel faces and the other four located near the channel corners. The corner equilibrium positions were found to exist only for Re larger than about 260. It was also shown that an increase in Re shifts the channel face equilibrium positions toward the channel center, whereas it shifts the corner equilibrium positions toward the channel corner. As the observation sites become downstream, the particles are more focused near the equilibrium positions. The distribution of the particles measured in a short distance from the channel inlet indicated that the lateral forces exerted on the particles located near the centers of the channel faces would be larger compared to the particles at the other positions in the cross-sections. [Preview Abstract] |
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