Modelagem da AplicaÃÃo de Ãgua com CanhÃes HidrÃulicos Sob Diferentes CondiÃÃes de Vento / Modeling gun sprinkler water application under different wind conditions.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

PRADO, Giuliani do. Modeling gun sprinkler water application under different wind conditions. 2008. 121 p. Thesis (Doctor Science in Agricultural Engineering) - Federal University of Lavras, Lavras, Minas Gerais, Brazil.2 Gun sprinklers are widely used, to apply water and vinasse, on sugarcane fields, that represent an important component of Brazilian economy. Guns sprinklers also provide a way to mechanize irrigation on small irregular shaped areas. Although raingun versatility has been proved, they have been criticized due to their low water application uniformity. Raingun low water application uniformity, that compromises crop yield and increases waste of water, energy, and fertilizers, is a consequence of the lack of knowledge about raingun water distribution characteristics. This unfamiliarity leads to inadequate design and operation criteria of irrigation systems in which gun sprinklers are used. Aiming to improve raingun application, thought a easier, and faster, characterization of raingun water application, the following procedures were developed and evaluated: i) a computer algorithm that, based on catch can water application measurements of each individual nozzle, simulates the radial water application profile of rainguns operating with two nozzles; ii) a computer algorithm that builds radial water application profiles based on catch can data collected during standard field evaluations of traveller irrigation machines; iii) a computer algorithm that adjust six empirical parameters of a wind distortion application pattern model, developed by de Richards &Weatherhead (1993), based on catch can data collected during standard field evaluations of sprinkler water application distribution; and iv) a computer algorithm that adjust six empirical parameters of a wind distortion application pattern model, developed by de Richards &Weatherhead (1993), based on catch can data collected during standard field evaluations of traveller irrigation machines. Values of water application rates, taken from radial profiles simulated by algorithms number i and ii, as described above, were very near to the ones taken from radial profiles determined during laboratory tests. The proximity among simulated and measured radial water application profiles was further reinforced by the proximity among Christiansen water uniformity values, computed for traveller irrigation machines based on those radial profiles. Comparisons of spatial water application patterns, simulated by the third algorithm and measured ones, showed that tests held under conditions of greater wind velocity were associated with greater values of average application rates and, consequently, greater values of average absolute deviations (from 2.168 to 3.611 mm h-1). A similar behavior was observed when comparing measured water application depth values with depth values simulated by the algorithm number iv. Averages of absolute deviation values also increased with wind velocity values observed during the tests (from 1.521 to 2.307 mm). These results demonstrate that with the help of the proposed algoritms it is possible: i) to decrease the number of standard field tests required to determine raingun radial water application profile; ii) to determine raingun radial water application profile directly from data collect at standard field evaluations of travel irrigation machines; and iii) to adjust the empirical parameters of the wind distortion application pattern model developed by de Richards &Weatherhead (1993) using catch can data collected at standard water distribution tests or collected at standard field evaluations of traveller irrigation machines.

ASSUNTO(S)

engenharia de agua e solo

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