Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session Q10: Multiphase Flows: General |
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Chair: Abhinandan Chowdhury, Savannah State University Room: Georgia World Congress Center B215 |
Tuesday, November 20, 2018 12:50PM - 1:03PM |
Q10.00001: Experimental study on the oil-water separation for marine applications Linfeng Piao, Hyungmin Park We perform a series of water-tunnel experiments to investigate the dynamic flow characteristics of oil-water mixture flows inside the channel of the oil-water separator developed for collecting and separating the marine spilled oils while varying the water hold-up and wave height. Our main focus is to understand the mechanism to determine the efficiency of oil recovery in the system. The oil-recovery rate decreases with increasing water hold-up and wave height; above 70% is achieved with a wave height (4-5 times of the channel height) but is dropped to 50% when water hold-up increases to 0.6. After analyzing the dynamics of flow patterns, two typical flow patterns are identified: wavy oil-water interface and dispersed oil phase, which are found to strongly affect the performance of oil recovery of the device. In general, as the water hold-up (or wave height) increases, the oil-recovery rate decreases while the dispersed phase of oil increases in the channel. Finally, we develop a theoretical model to predict the oil-recovery rate under the given operating conditions and to suggest a strategy to maximize the oil-recovery rate in the real marine operations. |
Tuesday, November 20, 2018 1:03PM - 1:16PM |
Q10.00002: Thermo-reflectance wall temperature measurement in annular two-phase flow Jason Chan, Brian E Fehring, Roman W Morse, Kristofer M Dressler, Gregory Nellis, Arganthael Berson A thermo-reflectance method to measure wall temperature in two-phase annular flow is described. In high heat flux conditions, momentary dry-out occurs as the liquid film vaporizes, resulting in dramatic decreases in heat transfer coefficient. Simultaneous liquid and vapor thermo-reflectance measurements allow calculations of instantaneous and time-averaged heat transfer coefficients. Validation, calibration and uncertainty of the technique are discussed. |
Tuesday, November 20, 2018 1:16PM - 1:29PM |
Q10.00003: Heat transfer measurements in pulsed annular flow using non-invasive temperature technique Roman W. Morse, Brian E Fehring, Jason Chan, Kristofer M Dressler, Arganthaël Berson, Gregory Nellis A single species vertical two-phase oscillatory annular flow facility allows simultaneous measurements of film thickness and wall temperature using non-invasive optical techniques. Long pulse trains allow accurate phase averaging of data. Heat transfer coefficients between the wall and thin film are calculated from measured data and compared to steady-state heat transfer correlations in a variety of flow conditions with varying pulse frequency, pulse amplitude and wall heating. |
Tuesday, November 20, 2018 1:29PM - 1:42PM |
Q10.00004: Studying the effect of swirl ratio on air-blast atomization in a canonical two-fluid atomizer Lam Xuan Vu, Robert M Chiodi, Olivier Desjardins Sprays are ubiquitous in engineering applications ranging from medical coatings to fuel sprays. Air-blast atomization is a process whereby a high-speed gas destabilizes a low-speed liquid leading to a series of instabilities which subsequently forms a spray. In this study, we present simulations of air-blast atomization in a canonical two-fluid atomizer at a fixed liquid and gas Reynolds number and varying swirl ratio. Simulations are performed using a conservative finite volume flow solver with phase tracking handled using an un-split, geometric volume of fluid method. We validate our simulations by comparing velocity and volume fraction statistics to experiments. We then extract detailed measurements such as droplet distribution and break-up length, highlighting the effect of swirl ratio on spray characteristics. |
Tuesday, November 20, 2018 1:42PM - 1:55PM |
Q10.00005: Electrifying an airblast atomizer and its effect on the flow field near the exit region Julie K Bothell, Timothy B Morgan, Danyu Li, Thomas Burtnett, Theodore J. Heindel, Alberto Aliseda, Nathanael Machicoane, Katarzyna Matusik, Alan L Kastengren Using the Advanced Photon Source at Argonne National Laboratory, high-resolution focused beam X-ray measurements are acquired and used in studying break-up mechanisms in the near-field region of an airblast atomizer. The nozzle used in the experiments is a two-fluid coaxial airblast atomizer with inner liquid flow rates that are within the laminar regime and outer air flow rates in the turbulent regime. This study works to determine the effect of electrifying the liquid portion of the spray. The average mass distribution and standard deviation are two of the measures used to examine the extent to which the flow direction and break-up can be manipulated. Electrifying the nozzle is explored as a method of real-time control of the spray field. |
Tuesday, November 20, 2018 1:55PM - 2:08PM |
Q10.00006: Numerical simulations of acoustically excited spray atomization Mahesh Natarajan, Olivier Desjardins The efficiency of a gas turbine is largely dependent on the combustion process between the liquid fuel and the oxidizer. The mixing of the the fuel vapours and the incoming air is critical to the combustion process, and the primary factor affecting vaporization is the atomization of the fuel spray. Experiments [1] have shown that high-amplitude acoustic waves are effective in controlling breakup and enhancing atomization of liquid sprays. We perform numerical simulations to investigate the dynamics of spray breakup of a water jet in the presence of transverse, standing acoustic waves. In agreement with experiments, it is observed that high-amplitude sound waves ~170 dB can have a significant effect on spray atomization. The jet location along the standing wave generated in the chamber is found to be a major factor affecting breakup and atomization. The compressible flow equations are solved, and the multiphase treatment uses a Volume of Fluid (VOF) approach with a piecewise linear interface calculation (PLIC) for the interface reconstruction. [1] Ficuciello, A., Blaisot, J., Richard, C., and Baillot, F. Physics of Fluids, 29(6):067103, 2017. |
Tuesday, November 20, 2018 2:08PM - 2:21PM |
Q10.00007: Study on dual-nozzle jet flows for the application of liquid atomization Daehyeon Choi, Juho Lee, Eunsoo Park, Jungwon Byun, Hyungmin Park The liquid atomization through a gas-phase jet flow has various applications of coating, cooling, and material processing. Most studies used a single-stage nozzle, but multi-stage configuration is considered to overcome its limitations. In this study, we experimentally study jet flows through two annular nozzles (upper and lower). To optimize the jet flow, we vary parameters like the pressure of each nozzle, the angle of the lower nozzle, distance between upper and lower nozzles, and so on. For each configuration, the single-phase gas jet flow is measured with PIV quantified focusing on the size of backflow region, turbulent intensity, and the streamwise momentum. It is found that the turbulence intensity and streamwise momentum increase downstream area as the lower nozzle angle increases, and the higher upper nozzle pressure is required to suppress the back flow. To support our understanding, we do preliminary tests of water (and glycerin) atomization and measure the size distribution of atomized droplets. Finally, we try to propose a model for predicting the size of atomized particles according to dual-nozzle configurations. |
Tuesday, November 20, 2018 2:21PM - 2:34PM |
Q10.00008: Proton Radiography of Explosively Dispersed Metal Particles while Under Vacuum Kyle Hughes, Katherine Prestridge, Nam-Ho Kim, Raphael Haftka, S Balachandar A series of experiments performed at Los Alamos National Laboratory is aimed to provide validation data for numerical simulations performed at the PSAAPII Center of Compressible Multiphase Turbulence (CCMT). Five explosive tests were performed. Approximately 2.8 g of PBX-9501 was initiated by a RP-80 detonator. A 13 x 13 mm cylindrical packet of 100 µm steel particles was dispersed by the explosive. A time-series of 21 proton radiography images were collected at 2 µs temporal resolution, allowing penetration of the explosive products at early time and extraction of the particle fronts. One of the challenges in simulation of the explosive dispersal of particles is the compaction model at early times and the subsequent particle collisions. To ease the modeling burden, two experimental design decisions were made to simplify the physics present. First, the experiments were done under vacuum. The removal of the ambient gas medium prevents the formation of an air-shock to propagate over the bed, subjecting the particles only to the contact discontinuity formed by the explosive product front moving into vacuum. Second, the volume fraction of the particle bed was reduced by substituting hollow glass microspheres for a portion of the steel particles. |
Tuesday, November 20, 2018 2:34PM - 2:47PM |
Q10.00009: High-speed x-ray imaging of atomization in an aircraft swirler geometry Brandon A. Sforzo, Katarzyna E. Matusik, Alan L. Kastengren, Christopher F. Powell High speed x-ray phase-contrast imaging experiments have been conducted at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory to examine the complex liquid spray and surface interaction phenomena within a modified aircraft fuel swirler. Air was supplied to a standardized aircraft swirler geometry, which was 3D printed with acrylic to maximize x-ray transparency. Water was used as a surrogate for fuel and supplied to the standard hardware at relevant flow conditions. Time resolved imagery of operations with either the pilot or main fuel circuit illustrate liquid impingement on the inner walls of the swirler and filming, with thicknesses up to several orifice diameters on the surface. These data can aid the evaluation of existing computational tools, and their ability to predict the aerodynamic breakup and surface interactions in these devices. |
Tuesday, November 20, 2018 2:47PM - 3:00PM |
Q10.00010: Large-Eddy Simulation of a Liquid Jet in Supersonic Crossflow Michael Benjamin Kuhn, Olivier Desjardins High-fidelity simulations can provide key insights in understanding the detailed physics of liquid atomization in scramjet engine combustion. Particularly in the case of cold-start, simulations of a liquid jet in supersonic crossflow complement experiments and can inform injector design. For this target problem, we have developed an all-Mach, compressible multiphase flow solver that combines a robust semi-Lagrangian scheme, which handles discontinuous transport at interfaces and shocks, with a low-dissipation transport scheme to accurately represent turbulence in smooth regions. Applying this solver, we perform large-eddy simulation to explore this relevant flow from qualitative and and quantitative perspectives, analyzing liquid plume trajectory, droplet size distribution, and wavelength of instabilities. |
Tuesday, November 20, 2018 3:00PM - 3:13PM |
Q10.00011: Identification of the Effective Diffusivity Coefficient of Polydisperse Spherical Suspension by using Random Point Approximation Abhinandan Chowdhury The so-called Random Point Approximation (RPA) is applied to identifying the effective diffusivity of a polydisperse spherical suspension. The RPA is based on truncated Volterra-Wiener Expansion (VWE) with basis function which is a random point function of perfect-disorder type. The VWE is applied consistently to derive the equations for the kernels. The contributions of the different kernels to the overall (effective) modulus are identified. An approximate model based on power-series expansion of the kernels with respect to the volume fraction is developed. It is argued that the contribution of the pure binary interaction (two-sphere solution) is negligible for moderately concentrated suspensions. The quadratures that give the contribution to the effective modulus are derived. The issue connected with the application of the fourth-order (one-sphere solution) are tackled, by evaluating some new kind of integrals. |
Tuesday, November 20, 2018 3:13PM - 3:26PM |
Q10.00012: Air entrainment and underwater noise of breaking waves Qiang Gao, Grant Deane, Lian Shen Breaking waves and bubbles play an important role in many upper-ocean physical processes, including enhancement of air-sea gas and momentum transfer and wave noise generation. In this study, we perform numerical simulations for wave breaking and bubbly flows using a new simulation method that computes resolved bubbles and subgrid-scale bubbles dynamically. Bubbles larger than the grid size are directly captured by a coupled level-set and volume-of-fluid method. Subgrid-scale bubbles are modeled using a four-way coupled polydispersed two-fluid model. We calculate the underwater noise based on a sound generation model, bubble identification procedure for resolved bubbles, and bubble entrainment modeling for subgrid scale bubbles. By analyzing the data from our simulation results, we investigate the air entrainment and sound generation in breaking waves. The results show that our numerical method can capture the wave breaking and air entrainment processes accurately. A comparison of calculated and observed wave noise will be presented and discussed. |
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