A MATHEMATICAL MODEL FOR EVALUATING THE EFFECT OF WIND ON DOWNWARD-SPRAYING RAINFALL SIMULATORS

Abstract

Rainfall simulators are used to study a variety of different processes (e.g., water erosion, infiltration, overland flow, irrigation, movement of agrochemicals, etc.). Wind affects field experiments that make use of rainfall simulators. Water-drop trajectories and velocities are altered, affecting water application and kinetic energy distributions.In this study, a three-dimensional numerical model was developed from the movement of individual drops after their release from the nozzle of a downward-spraying rainfall simulator. Drag forces, wind and gravity affect the original momentum of a single drop. Water application and kinetic energy were estimated from the coupling of a hydrodynamic model for drop movement, a drop generator representing a single full-cone spray nozzle, and an appropriate interception algorithm at the soil surface.The mathematical model should facilitate the selection of single full-cone spray nozzles and the size and configuration of the spray area for rainfall simulation in order to achieve high application uniformity values on the plot area. It can contribute to the adequate choice of nozzles as well as operating conditions necessary for laboratory and field purposes. Laboratory and field experiments were conducted to evaluate the adequacy of the proposed methodology.