The hypothesis of a linear relationship between wetted radius of gun sprinklers and wind velocity, as proposed by the Richards & Weatherhead model and widely used for simulation of water distribution by gun sprinklers under windy conditions, was evaluated in this study for medium-sized sprinklers. Distances from the sprinkler models used in this study (Agropolo/NY e Naan/5024) to the limit of the wetted area were determined through various field tests for upwind, downwind and crosswind conditions. Using the least square method it was found that, in relation to the no-wind radius, for each 1 m s-1 increase in wind velocity there was: (i) a distance reduction of 3.7% for upwind edge; (ii) a 3.0% decrease in distance for crosswind edge; and (iii) a 2.2% increase in distance for downwind edge. These results indicated that the linear relationship found between wetted radius and wind velocity was valid for the range of wind velocities considered in this study (0-3 m s-1).
uniformity tests; simulation; model by Richard & Weatherhead
