Water Dispersion and Distinction of Its Low-Head Efflux Down Through the Small Hole
Background. Low-head dispersion of water by impact with a hard surface is suitable for organization of water freezing on vertical surfaces and on horizontal attachments with icicles. When placing a set or sets of devices for water discharge, we have to consider radiuses of drops dispersion, and when irrigation of vertical surfaces, we have to consider the width of the moistened area and the height of drops flow-up above the striking face that depends on drops’ motion trajectory.
Objective. The task of our work is the detailed study of the primary (after discharge from a hole (a nozzle)) and also of the secondary liquid atomization on drops. It is of the utmost importance to explore the heights of drops dispersion and also width and height of wetting of a vertical surface depending on distance to the center of percussion.
Methods. At irrigation of horizontal attachments, the nearby holes for water discharge are disposed at close range or in the distance, which is smaller than the peak radius of drops dispersion, taking into account reduction in irrigation density when radius increases. At irrigation of vertical attachments, the distance from the center of percussion is selected, depending on objectives to the liquid spray rate and to the initial irrigation point under the striking face, which constitutes from 60 to 150 mm for conditions of research in the higher point.
Results. As a result of pilot studies of characteristics of primary (after discharge from the small-diameter hole) and secondary (after impact with the horizontal surface) drops dispersion, we found that the maximum height of drops upsurge is increased with the altitude of their recession and is horizontal-bias away from the center of percussion. The width of the wetted vertical surface area is determined geometrically on the basis of maximum dispersion ranges in a percussion plane.Conclusions. For the holes with the diameter of 1-2 mm in the reviewed pressure ranges (up to 350 mm w.c.), the correlation of discharge from pressure is straight-line, in contradistinction to level 0.5 for the correlation known for large-diameter holes. Dependencies to determine the range of primary drops dispersion after the discharge from a hole are obtained. Experimental data on the width of the wetted vertical surface area and on the maximum height of drops upsurge over the percussion plane are obtained.
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I.I. Pukhovyi and A.M. Postolenko, “Dispergation of water stream at its small charges and forming of icicles on wire attachments”, Visnyk Vinnyts'koho Politekhnichnoho Instytutu, no. 4, pp.119–123, 2012 (in Ukrainian).
I.I. Pukhovyi and M.O. Krivosheev, “Flow and water freezing on vertical surfaces by drops irrigation obtained by blow spraying”, Naukovi Visti NTUU KPI, no. 6, pp. 29–35, 2012 (in Ukrainian).
M. Rein, “Phenomena of liquid drop impact on solid and liquid surfaces”, Fluid Dynamics Res., vol. 12, no. 2, pp. 61–93, 1993.
L. Mishchenko et al., “Design of ice-free nanostructured surfaces based on repulsion of impacting water droplets”, Nanoletters, vol. 4, no. 12, pp. 7699–7707, 2010.
Fluid discharge from holes and fillings [Online]. Available: http://gidravl.narod.ru/istechenie.html
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