Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E46: Multiphase Flows |
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Sponsoring Units: DFD Chair: Arun Ramachandran, Univ of Toronto Room: LACC 506 |
Tuesday, March 6, 2018 8:00AM - 8:12AM |
E46.00001: A New Mechanism for the Wetting of a Solid Surface by Emulsion Droplets Arun Ramachandran, Suraj Borkar The wetting of a solid surface by the drop of an emulsion has traditionally been thought to be mediated by the formation of a liquid bridge that connects the drop and the surface. In this experimental work, an alternative mechanism was observed. When a glycerol drop suspended in a high molecular weight silicone oil approached a mica surface or a plasma treated SU-8 surface under the influence of gravity, islands of glycerol were observed to grow on the substrate. Wetting of the surface then occurred by the merging of the parent drop with one of nucleated sites. Scaling relationships were developed to describe the film height and the instant of time at which the parent drop merges with the islands. This work has revealed new variables that could be potentially used to control wetting: the solubility of the drop in the medium, the diffusivity of the drop phase in the medium and surface modification (to tune nucleation rates). The fundamental effect discovered here will guide the tailoring of emulsion-based coatings or paints to have specific wetting times. |
Tuesday, March 6, 2018 8:12AM - 8:24AM |
E46.00002: Variational 1-D Two-Fluid Model For Vertical Adiabatic Slug Flows Krishna Chaitanya Chetty Anamala, Alejandro Clausse, Martin Bertodano Numerical simulation of vertical adiabatic slug flows is performed using a variational one-dimensional (1-D) Two-Fluid Model (TFM), that incorporates the wake entrainment instability to make the model dynamic. Use of the variational TFM requires formulation of the inertial coupling coefficient to define the kinetic coupling between the phases. Using a lumped parameter model for flow over two cylindrical bubbles, the inertial coupling coefficient for slug flow wake entrainment phenomena is obtained. A variational 1-D TFM linear stability analyses comprising the characteristics and the dispersion relation and non-linear numerical simulations are performed, to demonstrate the wake entrainment instability leading to formation of long Taylor bubbles. Finally, the wavelengths, amplitudes and propagation velocities of the void waves from non-linear simulations are validated with two sets of experimental data. |
Tuesday, March 6, 2018 8:24AM - 8:36AM |
E46.00003: Bidisperse particle-laden flows down an incline. Claudia Falcon, David Arnold, Michael Lindstrom, Jeffrey Wong, Andrea Bertozzi
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Tuesday, March 6, 2018 8:36AM - 8:48AM |
E46.00004: Resuspension of heavy micro-particles in elongational flow. Raphael Jeanneret, Alex Groisman, Vasily Kantsler In this study, we explore re-suspension of non-Brownian spherical particles from under a flow directed upwards from the surface. The flow has been arranged in a microfluidic channel enabling detailed measurements of the particle lift. Simple dimensional arguments predict that for a flow with normal component of the velocity near the bottom surface, the particle lift against the gravity does not depend on the particle size within a range of the particle radii. The upper and lower limits of this range could be determined from Reynolds number on a particle to be below unity and the particle diffusion length against the gravity to be less than the particle size. This provides a range of sizes where the phenomenon can take place. For the polystyrene particles or micro-organisms, the range can be estimated from a few to a thousand microns. Our experiments with polystyrene beads reveal a very weak dependence of the lift event versus the radius of the beads, while the small discrepancy between the prediction and the experiment is attributed to the details of the flow arrangement. The results suggest that the re-suspension process indeed depends on the strength of the flow and does not depend on the size of the re-suspended particles within the considered limits. |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E46.00005: Effect of lift force and hydrodynamic torque on fluidization of non-spherical particles Ivan Mema, Vinay Mahajan, Barry Fitzgerald, Johan Padding Recent years have witnessed a big increase in usage of renewable biological materials as source for energy and chemical production. In most equipment used in this process, particles are suspended in a gas flow, such as in gas-fluidized beds. Numerical models of these processes approximate particles as spheres, thus limiting complexities encountered with hydrodynamic forces. However, spheres are not representative of dried and milled biomass particles, which are usually characterised by an elongated shape. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E46.00006: Large Eddy Simulations of Particle-Laden Turbulent Channel Flow Anand Samuel Jebakumar, Kannan Premnath, John Abraham A Lattice-Boltzmann based Large-Eddy Simulation (LES) solver is developed to simulate particle-laden turbulent flows. The Smagorinsky model is employed to account for the sub-grid scale stresses. The solver is first assessed for its accuracy in single-phase flows by comparing LES results for a turbulent channel flow with DNS results. Quantitative agreement within 5% of the mean velocity and the turbulent kinetic energy values across the cross-section of the channel, for grid sizes up to 5 times the Kolmogorov length scale, is achieved. Particle-laden flows are then simulated. It is known that when the particle Stokes number is close to unity, particles concentrate near the wall due to turbophoresis. Initial LES show that as the grid size increases, the predicted particle concentration near the wall increases. This is due to the inability of the LES to capture smaller isotropic eddies which cause particle dispersion near the wall. Two methods are adopted to resolve this issue: i) the addition of a random velocity to the filtered LES velocity to mimic random-walk ii) local grid refinement near the wall to capture the smaller eddies. Simulations with the methods show that while they are both capable of addressing the issue, the local refinement is the more robust approach. |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E46.00007: Phase Field Modeling of Melting, Resolidification, and Elastic Response of Metallic Powder-Substrate Interaction in Selective Laser Melting Jiqin Li, Tai-Hsi Fan Selective laser melting of metallic powders has been broadly applied in additive manufacturing process for building complicated parts that are otherwise difficult to manufacture by conventional methods. However, the control of surface quality and elimination of defects in AM produced parts is of a great challenge due to incomplete melting of powders and gas entrapment in the AM process. There is a great need of resolving the small scale process dynamics at the powder level. We present the interplay of solid-liquid phase transition, interfacial deformation, thermal capillary flow, and thermal elasticity involved in powder-substrate interaction upon selective laser melting. A phase field formulation is derived from irreversible thermodynamics to describe the transient evolution of three phases in a 2D space. By considering the temperature dependent material properties, the dynamics of phase transition and interfacial deformation during the fusion process are resolved computationally along with transient temperature distribution and the thermal stress in the substrate. The integrated modeling framework has captured the thermal fluid-structure interactions during the laser melting process, and can be extended to interactions of many powders for the prediction of surface defects. |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E46.00008: A numerical study of the interaction between particles and shock layer applied to Mars reentry problem. Gentien Marois, Philippe Villedieu, Julien Mathiaud Mars exploration began in 1962 with the Russian space probe « Mars 1 ». Technological advances make possible an exploration by the end of this century. However, several issues need to be addressed. One of them is the presence of dust and water droplets in Mars atmosphere. During reentry, those particles can impact the body, damage the Thermal Protection System (TPS) and increase the heat flux. |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E46.00009: One Experimental Observation of Steady Standing Wave in Co-flow System Zeyi Zhang, Chunmei Zhou, Liqiu Wang Dripping and jetting are two common regimes of the co-flow system. However, we usually observe wavy jets on the transition boundary between the dripping regime and the jetting regime. In this paper, we report one experimental observation of the steady standing wave in the co-flow system near the transition boundary. With this observation, we further examine the steady standing wave induced by the downstream boundary condition with respect to both the absolute instability and the convective instability. The downstream cross-sectional change can potentially stabilize the co-flow interface. |
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