Drop Size Distributions for Irrigation Sprinklers

Abstract

A set of drop size distribution data is presented covering a wide range of sprinkler types including single nozzle impact sprinklers with straight bore and square nozzles, and sprayheads with various types of deflector plates. Drop sizes were measured by the laser-optical method and comparisons with other types of drop size measurement techniques are presented. Distributions are parameterized with an exponential function, and a method is provided to estimate the parameters given the sprinkler type, nozzle size, and pressure head. Keywords. Irrigation, Sprinklers, Drop size. S prinkler irrigation can be defined as any irrigation system which distributes water as discrete droplets through the air. The variety of sprinkler devices available has increased dramatically in recent years, from the conventional single or double nozzle impact sprinkler with many types of nozzles to various types of deflection-plate sprinklers which influence the drop sizes and water distribution patterns over a wide range of flow rates and pressures. Accurate knowledge of drop size distributions for sprinklers is important because evaporation and drift losses are controlled by the extreme small size ranges and drop impact energy on the soil is determined primarily by the largest size ranges. Selection of a specific sprinkler package for a sprinkler system operating on particular soil, slope, crop, and climate conditions will be aided by knowledge of the drop sizes. Several articles have been published describing the drop size distributions of specific types of sprinklers (Kohl, 1974; Kohl and DeBoer, 1984; Solomon et al., 1985; Kohl and DeBoer, 1990). The reported data were collected using pellet, stain, and photographic methods. This article presents additional data using a laser-optical method compared with some distributions determined by some of the previously used methods, so that the entire body of published data is more comparable. The main objective is to parameterize the data and present a method to predict the parameters as a function of nozzle size and pressure.

Evaporation Research: Review and Interpretation

“…Droplet size distributions for various sprinkler and spray head types are available for evaporation model input (Dadiao and Wal lender 1985;Kohl and DeBoer 1985;Solomon et al 1985;Kincaid et al 1996). Thompson (1993b) and Kincaid and Longely (1989) noted that under similar environmental conditions the fraction of the applied volume that is lost to spray evaporation increases as droplet di ameter decreases.…”

Polymer and sprinkler droplet energy effects on sugar beet emergence, soil penetration resistance, and aggregate stability

“…The applied water had a droplet size distribution with a median volumetric drop diameter (d 50) of 0.9-1.0 mm and low to moderate droplet energy, 5-8 J kg -1 , as estimated from Kincaid (1996) and Kincaid et al (1996). We irrigated the pots on the second, ninth, and fourteenth day after planting (DAP), applying about 11 mm of water each day.…”

Measurement of Sprinkler Droplet Size

“…Details of Kincaid et al (1996) and Solomon et al (1991). A total of 10,000 droplets were measured at each radial position.…”

“…Laser technology (Kincaid et al, 1996) can be used to acquire droplet distribution information in a relatively short time, but the capital investment is substantial or the equipment may not be readily available. In contrast, a labor-intensive method that uses baking flour as a droplet catchment medium was used extensively before the advent of the laser technology (Kohl, 1974).…”