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contributor authorLow, T. B.
contributor authorList, Roland
date accessioned2017-06-09T14:23:16Z
date available2017-06-09T14:23:16Z
date copyright1982/07/01
date issued1982
identifier issn0022-4928
identifier otherams-18394.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4154394
description abstractThe collision, coalescence and breakup of single raindrop pairs were studied at terminal velocities and laboratory pressure (100 kPa) in 761 collision experiments (out of 14 000 attempts). Six size combinations were used with drop pair diameters of [0.18;.0.0395 cm], [0.40; 0.0395 cm], [0.44; 0.0395 cm], [0.18; 0.0715 cm], [0.18; 0.10 cm] and [0.30; 0.10 cm]. For averaging purposes the experiments were repeated over one hundred times for each pair. The new coalescence efficiencies and fragment size distributions in breakup turned out to be consistent with those of McTaggart-Cowan and List (1975b) and permitted the combination of the two data sets into a single data bank spanning essentially the entire range of raindrop sizes. The analysis addressed three main geometric shapes formed by the drops after initial contact, namely, filaments, sheets and disks, and the fragment size distributions after breakup. Significant collisional growth, i.e., coalescence, occurred only when drops <0.06 cm in diameter were struck by larger ones. An empirical equation involving collision kinetic (CKE) and surface tension energies was developed to approximate the observed coalescence efficiencies. Breakup fragment size distributions normally show two or three peaks, one close to the size of the large drop of the collision pair, one at times (for filaments) reflecting the small drop, and the third centered at sizes below the small drop diameter. At high energy collisions involving larger drops the mechanism most favorable for coalescence was the disk shape because with its high deformation it is able to dissipate the most energy either through air drag or by internal viscosity through oscillations. The lowest collision energy for breakup is required for filaments; more is needed for sheets and most for disks.
publisherAmerican Meteorological Society
titleCollision, Coalescence and Breakup of Raindrops. Part I: Experimentally Established Coalescence Efficiencies and Fragment Size Distributions in Breakup
typeJournal Paper
journal volume39
journal issue7
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/1520-0469(1982)039<1591:CCABOR>2.0.CO;2
journal fristpage1591
journal lastpage1606
treeJournal of the Atmospheric Sciences:;1982:;Volume( 039 ):;issue: 007
contenttypeFulltext


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