Atomization of undulating liquid sheets

2007 ◽  
Vol 585 ◽  
pp. 421-456 ◽  
Author(s):  
N. BREMOND ◽  
C. CLANET ◽  
E. VILLERMAUX
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Free Edge ◽  
Liquid Sheet ◽  
Drop Size Distribution ◽  
Secondary Instability ◽  
Operating Conditions ◽  
Helmholtz Instability ◽  
Liquid Sheets ◽  
Unique Parameter

The fragmentation of a laminar undulating liquid sheet flowing in quiescent air is investigated. Combining various observations and measurements we propose a sequential atomization scenario describing the overall sheet–drop transition in this configuration. The undulation results from a controlled primary Kelvin–Helmholtz instability. As the liquid travels through the undulating pattern, it experiences transient accelerations perpendicular to the sheet. These accelerations trigger a secondary instability responsible for the amplification of spanwise thickness modulations of the sheet. This mechanism, called the ‘wavy corridor’, is responsible for the sheet free edge indentations from which liquid ligaments emerge and break, forming drops. The final drop size distribution is of a Gamma type characterized by a unique parameter independent of the operating conditions once drop sizes are normalized by their mean.

Break-Up of Threads From Laminar Open Channel Flow Influenced by Cross-Wind Gas Flow

2014 ◽  
Author(s):  
Jens Kamplade ◽  
Tobias Mack ◽  
Andre Küsters ◽  
Peter Walzel
Keyword(s):  
Size Distribution ◽  
Channel Flow ◽  
Gas Flow ◽  
Drop Size ◽  
Open Channel ◽  
Open Channel Flow ◽  
Drop Size Distribution ◽  
Operating Conditions ◽  
Breakup Process ◽  
Breakup Length

The breakup process of threads from laminar operating rotary atomizer (LamRot) is in the scope of this investigation. A similarity trail is used to investigate the influence of the thread deformation within a cross-wind flow on the thread breakup process. The threads emerge from laminar open channel flow while the liquid viscosity, the flow rate, the pipe inclination towards the gravity as well as the cross-wind velocity is varied. The breakup length and drop size distribution are analyzed by a back-light photography setup. The results thus obtained are compared with results of previous examination by Schröder [1] and Mescher [2]. It is found that the breakup length decreases and that the drop size grows with rising cross-wind intensity, while the width of the drop size distribution increases. At the same operating conditions, the breakup length for laminar open channel flow is smaller compared to completely filled capillaries. In contrast to this observation, the drop size distribution remains nearly unchanged. The critical velocity for the transition from axisymmetric to wind-induced thread breakup was found to be smaller than for completely filled capillaries.

Physically-Based Drop Size Distribution Evolution of Atomized Drops

2010 ◽  
Author(s):  
Moussa Tembely ◽  
Arthur Soucemarianadin ◽  
Christian Le´cot
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Size Distribution ◽  
Drop Size ◽  
Chemical Properties ◽  
Drop Size Distribution ◽  
Operating Conditions ◽  
Design Parameters ◽  
New Device ◽  
Physically Based

We report in this work the evolution of a physically-based drop size-distribution of atomized drops coupling the Maximum Entropy Formalism (MEF) and the Monte Carlo method. The atomization is performed using a Spray On Demand (SOD) print-head which exploits ultrasonic generation via a Faraday instability. The physically-based distribution is a result of the coupling of a MEF specific formulation and a general Gamma distribution. The prediction of the drop size distribution of the new device is performed. The dynamic model which prediction capability is fairly good is shown to be sensitive to operating conditions, design parameters and physico-chemical properties of the fluid. In order to achieve the drop size-distribution evolution, we solve the distribution equation, reformulated via the mass flow algorithm, using a convergent Monte Carlo Method able to predict coalescence of sprayed droplets.

Airblast Atomization: Studies on Drop-Size Distribution

1982 ◽  
Vol 6 (5) ◽  
pp. 323-327 ◽  
Author(s):  
N. K. Rizk ◽  
A. H. Lefebvre
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution

scholarly journals Evaluation of Gamma Raindrop Size Distribution Assumption through Comparison of Rain Rates of Measured and Radar-Equivalent Gamma DSD

2014 ◽  
Vol 53 (6) ◽  
pp. 1618-1635 ◽  
Author(s):  
Elisa Adirosi ◽  
Eugenio Gorgucci ◽  
Luca Baldini ◽  
Ali Tokay
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Rain Rate ◽  
Hydrological Cycle ◽  
Drop Size Distribution ◽  
Dual Polarization ◽  
Raindrop Size Distribution ◽  
Radar Measurements ◽  
Raindrop Size ◽  
Rain Rates

AbstractTo date, one of the most widely used parametric forms for modeling raindrop size distribution (DSD) is the three-parameter gamma. The aim of this paper is to analyze the error of assuming such parametric form to model the natural DSDs. To achieve this goal, a methodology is set up to compare the rain rate obtained from a disdrometer-measured drop size distribution with the rain rate of a gamma drop size distribution that produces the same triplets of dual-polarization radar measurements, namely reflectivity factor, differential reflectivity, and specific differential phase shift. In such a way, any differences between the values of the two rain rates will provide information about how well the gamma distribution fits the measured precipitation. The difference between rain rates is analyzed in terms of normalized standard error and normalized bias using different radar frequencies, drop shape–size relations, and disdrometer integration time. The study is performed using four datasets of DSDs collected by two-dimensional video disdrometers deployed in Huntsville (Alabama) and in three different prelaunch campaigns of the NASA–Japan Aerospace Exploration Agency (JAXA) Global Precipitation Measurement (GPM) ground validation program including the Hydrological Cycle in Mediterranean Experiment (HyMeX) special observation period (SOP) 1 field campaign in Rome. The results show that differences in rain rates of the disdrometer DSD and the gamma DSD determining the same dual-polarization radar measurements exist and exceed those related to the methodology itself and to the disdrometer sampling error, supporting the finding that there is an error associated with the gamma DSD assumption.

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