Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session HD: Liquid Breakup and Coalescence II |
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Chair: Osman Basaran, Purdue University Room: Hilton Chicago Continental A |
Monday, November 21, 2005 1:20PM - 1:33PM |
HD.00001: Bag Breakup of Liquid Jets in Gaseous Crossflow Khaled Sallam, Chee-Loon Ng, Ramprakash Sankarakrishnan The present investigation carried out measurements of a variety of properties for nonturbulent and turbulent round liquid jets exposed to gaseous crossflows within the bag breakup regime, as follows: properties of column and surface waves, number of bags along the liquid column, droplets size after breakup, droplets velocity distributions after breakup, and trajectories of the liquid droplets. Pressure-fed supercavitating nozzles having sharp-edged orifices were used to create uniform nonturbulent round liquid jets while injector with length to diameter ratio greater than 40 were used to create the turbulent round liquid jets. The liquid jets were injected across a windowed section of a wind tunnel. The waves and breakup processes were observed using high speed imaging and single and double pulse shadowgraphy. New findings of leeward surface waves along nonturbulent liquid jets in crossflow were captured by observing the downwind side of the liquid jet. Phenomenological analyses were effective to interpret and correlate the new measurements. [Preview Abstract] |
Monday, November 21, 2005 1:33PM - 1:46PM |
HD.00002: Breakup Properties and Trajectories of Turbulent Round Liquid Jets in Gaseous Crossflows Kyungjin Lee, Francisco J. Diez, Christian Aalburg, Khaled A. Sallam An experimental investigation of breakup properties and trajectories of turbulent round liquid jets in uniform gaseous crossflows is described. Pulsed shadowgraphy and holography were used to measure conditions required for liquid column breakup as a whole, rates of turbulent primary breakup and liquid column trajectories. Liquid column breakup lengths are shorter than those of nonturbulent liquid jets indicating enhancing effects of liquid turbulence on liquid column breakup. Rates of breakup and trajectories are in good agreement with earlier measurements for nonturbulent liquid jets. Phenomenological analyses were effective to help interpret and correlate the measurements. [Preview Abstract] |
Monday, November 21, 2005 1:46PM - 1:59PM |
HD.00003: Pinch-off of Electrified Jets R.T. Collins, M.T. Harris, P. Doshi, O.A. Basaran Breakup of electrified jets is important in applications as diverse as spraying, fiber spinning, separations, and mass spectrometry. Breakup of a perfectly conducting, incompressible Newtonian liquid jet surrounded by a passive insulating gas that is stressed by a radial electric field is studied by a temporal analysis. An initially quiescent jet is subjected to axially periodic shape perturbations and the ensuing dynamics are followed numerically until pinch-off by finite element analysis. Computed results are shown to accord well with linear theory for short times. Breakup times and ratios of volumes of primary to satellite drops are reported over a wide range of electric Bond numbers (electric/surface tension force), Reynolds numbers (inertial/viscous force), and disturbance wave numbers. Effects of surface charge on interface overturning are investigated. The dynamic interplay between electrostatic and capillary stresses and the influence of electrostatic stresses on local scaling laws governing pinch-off are also examined. [Preview Abstract] |
Monday, November 21, 2005 1:59PM - 2:12PM |
HD.00004: Repeated formation of fluid threads in breakup of a surfactant-covered jet Patrick McGough, Osman Basaran Breakup of thin threads is observed when fluid drips from leaky faucets, drops are emitted from inkjet printers, and miniscule nuclei and mammoth stars fission. As a surfactant-covered liquid jet approaches breakup, its profile consists of a periodic pattern of large drops connected by thin threads. Near the locations where the threads join the drops, simulations show that a series of thinner threads arise naturally as the jet pinches off. That threads can continue to form repeatedly without addition of noise when surfactants are present is unexpected and stands in direct contrast to earlier studies of surfactant-free systems. The thinning dynamics of successive threads are shown to be self-similar and approach Eggers's universal solution for clean interfaces as they become depleted of surfactant. [Preview Abstract] |
Monday, November 21, 2005 2:12PM - 2:25PM |
HD.00005: \textbf{Surfactant effects in dynamics and breakup of a contracting liquid filament} Qi Xu, Osman Basaran The effects of a monolayer of insoluble surfactant on the dynamics of contraction and breakup of a liquid filament in air are studied by solving numerically the Navier-Stokes system that governs the time evolution of the filament shape and the velocity and pressure fields within it and the time-dependent convection-diffusion equation that governs surfactant transport on the air-liquid interface. Five dimensionless parameters govern this free boundary problem: dimensionless filament half-length L, Ohnesorge number Oh (viscous/capillary force), dimensionless initial surfactant loading $\Gamma $, a parameter $\beta $ which provides a measure of the strength of the surfactant, and surface Peclet number Pe (convection/diffusion of surfactant). Computational results show that when Pe is low, Marangoni effects are weak and the dynamics closely resemble those of a surfactant-free filament. In contrast, when Pe is high, Marangoni stresses can prevent filament breakup via the end-pinching mode. Vorticity dynamics within the filament are also examined to help shed light on the fluid mechanics of the contraction process. [Preview Abstract] |
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