Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session ZC21: Atomization and Sprays |
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Chair: Zehao Pan, Princeton University Room: 250 E |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC21.00001: Study of the Modes Responsible for the Breakup of High-Speed Cylindrical Jets Injected into a Quiescent Gas Mohan Ananth, Mario F Trujillo The current study involves understanding the modes observed in the breakup of high-speed cylindrical jets using mean flow linear stability analysis and volume of fluid (VoF) simulations. Previous studies on the breakup of high-speed rectangular liquid sheets have shown the development of large wavelength sinuous modes, which are dominant at high gas shear layer thickness, leading to the complete breakup of the sheet. In addition, the perturbation kinetic energy in gas is dominant for the spatially growing sinuous mode. Extending the work to 3D cylindrical geometry, mean flow linear stability analysis shows that the helical (asymmetric) modes shift to higher wavelengths than the axisymmetric modes when the gas shear layer thickness is increased. The shift to higher wavelengths is also accompanied by the dominance of perturbation kinetic energy in gas compared to that in the liquid. Volume of Fluid simulations are performed for the high-speed cylindrical jets to observe the manifestation of perturbations in the non-linear regime leading to the complete breakup of the liquid jet. The VoF simulations show that the complete fragmentation of the jet is caused by large-wavelength helical modes, accompanied by a significant increase in gas shear layer thickness. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC21.00002: An Examination of the Maximum Entropy Formalism for Secondary Atomization Ahmad Faraz Badar, Mario F Trujillo The maximum entropy formalism (MEF) is an attractive approach to predict the size and velocity distributions of daughter droplets resulting from secondary atomization because it is based on satisfying physical conservation laws. However, a critical examination of the method shows that it cannot reliably predict secondary atomization statistics due to a multitude of reasons. Firstly, the MEF cannot predict the multi-modal nature of droplet size distributions as evidenced by experimentally obtained size distributions in the literature. Secondly, it over-predicts velocity distributions of daughter droplets because of its inability to capture the temporal nature of the breakup process. Efforts to improve the velocity predictions by the MEF through a variation of the parameters in its formulation show little to no improvement. Finally, mathematical inconsistencies in the properties of the continuous form of the information entropy function used in the MEF pose challenges to the validity of its utilization for secondary atomization. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC21.00003: Abstract Withdrawn
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Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC21.00004: Unraveling Spray Dynamics and Droplet Generation from an Energy Perspective Shyam Kumar Mutil House, Christopher J Hogan Jr., Steven A Fredericks, Jiarong Hong The droplet size distribution of sprays is influenced by numerous factors, including nozzle design, source pressure, working fluid properties, and external flow. Despite this complexity, sprays are governed by a straightforward energy balance, where the driving fluid power is partitioned into the rate of surface energy production associated with droplet formation, the viscous dissipation rate, and the droplet kinetic energy rate. While the surface energy term is commonly normalized to yield the spray efficiency, the latter kinetic energy term is more sparingly estimated. The kinetic energy of individual droplets influences droplet transport through quiescent air and droplet impact outcomes, which are particularly of interest in agricultural sprays, internal combustion fuel injectors, and spray coatings. Herein, we estimate droplet kinetic energy and develop a scaling relationship in terms of input spray parameters. Digital inline holography (DIH), combined with a novel machine learning based post-processing method for data extraction, is used to measure the spatial distribution of droplets and their temporal evolution. From this high-fidelity data obtained using DIH on different nozzles at three distinct locations—the center, half-span, and edge of flat fan sprays—under different tank pressures, we are able to estimate the kinetic and surface energy. This study aims to enhance understanding of energy distribution in sprays and optimize spray systems across applications. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC21.00005: Abstract Withdrawn
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Tuesday, November 26, 2024 1:55PM - 2:08PM |
ZC21.00006: Novel Tools for Atomization Simulation Analysis Brendan V Christensen, Mark F Owkes We present a comprehensive methodology for analyzing high-fidelity atomization simulations using the Atomization Simulation Statistics Extraction Tool (ASSET) to derive novel insights from liquid breakup events. This approach involves extracting statistics in addition to capturing the full geometry of the breakup and the surrounding flow field. These data are then systematically organized into a database using the Weighted Euler Characteristic Transform (WECT). This results in a vectorized representation of the breakup data, making it easily parsable, queryable, and ideal for advanced statistical analysis techniques. The goal of this work is to present the methodology and display the potential utility of easily accessible, vectorized atomization databases. |
Tuesday, November 26, 2024 2:08PM - 2:21PM |
ZC21.00007: Effect of Compressibility and Density Ratio on Two Phase Shear Layers zoe barbeau, Sanjiva K Lele Atomization occurs when a liquid jet from a nozzle is discharged into a stagnant or moving gas causing the gas-liquid interface to become unstable and break up into a collection of droplets. The objective is to simulate a simplified problem of planar two-phase mixing layer between a co-flowing liquid and high-speed gas stream in a compressible regime. A 6th order staggered, compact finite difference method with the 5-equation model, 2nd interface sharpening, localized artificial diffusivity, and no filtering is found to be robust for multiphase flows particularly high-density ratios with shocks and to have excellent agreement with linear stability theory when finite interface thickness effects are included1. The effect of compressibility is explored in the nonlinear regime in 2D simulations varying gas Mach number for a moderate gas Reynolds number and high gas Weber number. Overall, gas Mach number reduces the interface perturbation, growth rates, and momentum thickness at density ratio of 10 but does not significantly impact these attributes at density ratio of 1000. Preliminary simulations of the shear layer breakdown in 3D are planned. |
Tuesday, November 26, 2024 2:21PM - 2:34PM |
ZC21.00008: Pre-holes and holes: heterogeneities in liquid sheets of emulsion Sara Gonzalez, Emilie Dressaire Industrial and agricultural processes rely on sprays to deliver fluid to surfaces. A common way to tune the size of the spray droplets is by varying the composition of the liquid. For example, oil droplets in an aqueous phase modify the atomization dynamics and the size distribution of the secondary droplets. Observations of self-suspended liquid sheets indicate that the destabilization occurs as the sheet thickness becomes highly heterogeneous with isolated regions of low to zero thickness. To understand how the immiscible dispersed phase leads to thickness heterogeneities and eventually different spray properties, we investigate the dynamics of pre-holes (thin regions) and holes. We track the nucleation, position, and growth of pre-holes and holes as a function of the oil volume fraction, surface tension, and viscosity. We find that the growth rate of pre-holes decreases with oil phase viscosity and surface tension. Our findings demonstrate that the competition between viscous and capillary effects controls the formation and growth of heterogeneities in liquid sheets. |
Tuesday, November 26, 2024 2:34PM - 2:47PM |
ZC21.00009: Optimization of Interfacial and Mechanical Stresses during Room Temperature Aerosol Dehydration (RTAD) of Green Fluorescence Protein Zehao Pan, Junshi Wang, Howard A Stone, Maksim Mezhericher Rapid Room-Temperature Aerosol Dehydration (RTAD) is a new, scalable drying technology for pharmaceutical drug products. Compared to conventional spray drying, RTAD uses smaller droplets that quickly evaporate in ambient temperature, reducing thermal stress for thermally sensitive biologics. In this work, we used green fluorescence protein (GFP) as a model molecule of protein biologics to optimize the RTAD design. We studied the effects of surfactant, droplet size, and flow pattern on GFP fluorescence after drying and reconstitution. We found that the surfactant has a significant impact on the GFP fluorescence, especially when the droplet size is small. GFP fluorescence was also found to be affected by the flow pattern in the drying chamber. Using Computational Fluid Dynamics (CFD) simulations, we identified localized high-speed flow that creates strong circulation zones in the drying chamber, resulting in lower GFP fluorescence. |
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