Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session E7: Multiphase Flows: GeneralMultiphase
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Chair: Xiaolong Deng, Beijing Computational Science Research Center Room: 407 |
Sunday, November 19, 2017 4:55PM - 5:08PM |
E7.00001: The influence of liquid/vapor phase change onto the Nusselt number. Elena-Roxana Popescu, Catherine Colin, Sebastien Tanguy In spite of its significant interest in various fields, there is currently a very few information on how an external flow will modify the evaporation or the condensation of a liquid surface. Although most applications involve turbulent flows, the simpler configuration where a laminar superheated or subcooled vapor flow is shearing a saturated liquid interface has still never been solved. Based on a numerical approach, we propose to characterize the interaction between a laminar boundary layer of a superheated or subcooled vapor flow and a static liquid pool at saturation temperature. By performing a full set of simulations sweeping the parameters space, correlations are proposed for the first time on the Nusselt number depending on the dimensionless numbers that characterize both vaporization and condensation. As attended, the Nusselt number decreases or increases in the configurations involving respectively vaporization or condensation. More unexpected is the behaviour of the friction of the vapor flow on the liquid pool, for which we report that it is weakly affected by the phase change, despite the important variation of the local flow structure due to evaporation or condensation. [Preview Abstract] |
Sunday, November 19, 2017 5:08PM - 5:21PM |
E7.00002: Mechanistic study of slug formation in turbulent gas-laminar liquid multiphase flow in horizontal channels Sha Miao, Kelli Hendrickson, Yuming Liu We present numerical simulations of slug generation from stratified flow in horizontal channels for a turbulent-gas/laminar-liquid using a Fully-Coupled Immersed Flow (FCIF) solver. FCIF uses an immersed boundary method to couple an unsteady Reynolds Averaged Navier Stokes (uRANS) and a depth-integrated wave solver to efficiently simulate disparate flows on a single non-boundary conforming grid. We establish slug formation as a two-stage process. Initially, relatively short waves develop due to linear interfacial instability and then evolve into long solitary waves via wave coalescence due to nonlinear wave resonance. The gas-to-liquid energy transfer is first by interfacial shear stress and then ultimately by interfacial pressure forcing. We observe the interfacial pressure gradient first correlates with wave slope. In the second stage it correlates with elevation due to the competition between Bernoulli and viscous effects in the wave-influenced gas layer. Guided by these findings, we perform an asymptotic analysis on the second stage. This analysis shows the occurrence of slugging depends on the total flow rate and there exists a critical threshold above which waves grow faster than tri-exponential functions to form a slug. [Preview Abstract] |
Sunday, November 19, 2017 5:21PM - 5:34PM |
E7.00003: An Experimental Study Comparing Droplet Production by a Strong Plunging and a Weak Spilling Breaking Water Waves Martin Erinin, Dan Wang, David Towle, Xinan Liu, James Duncan In this study, the production of droplets by two mechanically generated breaking water waves is investigated in a wave tank. A strong plunging breaker and weak spilling breaker are generated repeatedly with a programmable wave maker by using two dispersively focused wave packets with the same wave maker motion profile shape (average frequency 1.15 Hz) and two overall amplitude factors. The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a high speed (650 Hz) cinematic digital in-line holographic system positioned at various locations along a horizontal plane that is 1 cm above the maximum wave crest height. The measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d \textgreater 100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the two breaking waves is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. [Preview Abstract] |
Sunday, November 19, 2017 5:34PM - 5:47PM |
E7.00004: Vortex-Induced Waves in Two-Phase Liquid-Liquid Flows past Bluff Body M. I. I. Zainal Abidin, Kyeong H. Park, Panagiota Angeli, Zhihua Xie, Lyes Kahouadji, Omar K. Matar Transverse cylinders of various sizes are used to generate vortex-induced interfacial waves in two-phase oil-water flows and to influence flow pattern transitions. The vortex shedding properties at different cylinder sizes and the resulting induced waves are studied experimentally with Particle Image Velocimetry (PIV) and high-speed imaging. The system consists of a 7 m long horizontal 37 mm ID acrylic pipe and different cylinders with diameters of 2, 5 and 8 mm, located in the water phase, 460 mm after the two phases come into contact. The cylinder generates waves with frequencies similar to the von Karman vortices and changes in vortex shedding properties at different cylinder size are reflected on the resulting interfacial wave characteristics. The presence of the transverse cylinder actuates the transition from stratified to dispersed flows; the boundary between the two patterns is shifted to lower mixture velocity with increasing cylinder size. Three-dimensional numerical simulation of the system is developed to assist in designing new system. [Preview Abstract] |
Sunday, November 19, 2017 5:47PM - 6:00PM |
E7.00005: Characterization of Flow Dynamics and Reduced-Order Description of Experimental Two-Phase Pipe Flow Bianca Viggiano, Olaf Skjæraasen, Murat Tutkun, Raul Bayoan Cal Multiphase pipe flow is investigated using proper orthogonal decomposition for tomographic X-ray data, where holdup, cross sectional phase distributions and phase interface characteristics are obtained. Instantaneous phase fractions of dispersed flow and slug flow are analyzed and a reduced order dynamical description is generated. The dispersed flow displays coherent structures in the first few modes near the horizontal center of the pipe, representing the liquid-liquid interface location while the slug flow case shows coherent structures that correspond to the cyclical formation and breakup of the slug in the first 10 modes. The reconstruction of the fields indicate that main features are observed in the low order dynamical descriptions utilizing less than 1$\%$ of the full order model. POD temporal coefficients $a_1$, $a_2$ and $a_3$ show interdependence for the slug flow case. The coefficients also describe the phase fraction holdup as a function of time for both dispersed and slug flow. These flows are highly applicable to petroleum transport pipelines, hydroelectric power and heat exchanger tubes to name a few. The mathematical representations obtained via proper orthogonal decomposition will deepen the understanding of fundamental multiphase flow characteristics. [Preview Abstract] |
Sunday, November 19, 2017 6:00PM - 6:13PM |
E7.00006: Falling dynamics of saddle-like particles. Luis Blay Esteban, John Shrimpton, Bharathram Ganapathisubramani Irregular particles freely falling under the effect of gravity through a viscous media describe various falling styles depending on the fluid and particle properties. Understanding the differences in dynamics between falling styles is relevant to many branches of science and engineering. Thin disks and rectangular plates have been widely investigated in the past and its motion has been classified under four different trajectory types: steady descent, fluttering, tumbling and chaotic. The type of trajectory depends on the Reynolds number of the particle (Re) and dimensionless particle inertia (I*). However, when these geometry of the particles are modified, the regime map is significantly altered. In this study, we carry out experiments with thin plates that have a square planform of different diagonal lengths (d) and different curvatures at the centre of the plate. The aim to investigate the effect of the bending angle on the particle dynamics and the regime map. These different particles are released in to quiescent fluid with similar initial conditions using a mechanism that employs active suction. Each particle was dropped multiple times from a height (h) sufficiently large (h/d \textgreater \textgreater 1) to allow the falling regime to fully develop during the observation. Particle falling trajectories were recorded with two high speed cameras at 60 frames per second so that the particle dynamics are temporally resolved during all parts of the particle descent. Results from the analysis of these trajectories and the resulting regime map for the plates with varying curvature will be presented. [Preview Abstract] |
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