Irrigation uniformity with medium size sprinklers part I: Characterizationof water distribution in no-wind conditions

In order to characterize water distribution with medium-sized sprinklers a number of single leg tests were conducted in no-wind conditions. The influe nce of sprinkler type, size and number of nozzles, jet-straightening vane ( VP), working pressure, riser height and the irrigation spacing were analyze d in these tests. In a large number of main nozzles, the effect of internal "turbulence" was found when the sprinkler operated at high pressure, imply ing an important depletion of both discharge and throw. This phenomenon onl y depends upon the internal design of the main nozzle when no manufacturing defects are present. When calculating the discharge-pressure fit equation in the case of circular nozzles, the mean discharge coefficient ranged from 0.96 to 1.00. The discharge coefficient was independent of the working pre ssure. In radial indoor tests, higher irrigation uniformity was achieved wh en the sprinkler operated with double nozzle than with a single nozzle. Whe ther the sprinkler incorporated a jet-straightening vane within the main no zzle or was located at 2 m aboveground, farther throw was also attained. Wi th VP, CU values decreased; whereas, at 2 m aboveground the uniformity was similar or slightly higher. These results are complemented with those achie ved in a set of single sprinkler tests in windy conditions, which are shown in the accompanying article.