Experimental Characterization of the Aerodynamic Wake of a High-Clearance Sprayer with Changing Operating Parameters

Abstract

HighlightsAir velocity data were measured at seven lateral positions across the width of a modern high-clearance sprayer at multiple vertical and downstream locations relative to the nozzles. Velocity components were measured in three directions.Complex flow patterns were present behind the sprayer tractor and rear tires. An upward velocity component was measured below and downstream of the nozzles at many of the sensor locations.Elevated turbulent kinetic energy was measured downstream of the structural elements required for reconfiguring the boom structure into the transport position.Abstract. With growing pressure for increased efficiency and productivity on large farms throughout North America, high-clearance sprayers have become large machines that are operated at relatively high speed when applying pesticides during the growing season. Minimizing pesticide drift remains paramount to the safe and responsible operation of these machines. With the aim of both improving the understanding of high-clearance sprayer wake features, and to aid in the validation of numerical models of a full-scale sprayer using computational fluid dynamics (CFD), time-averaged velocity components and turbulent kinetic energy (TKE) in the wake of a sprayer were measured and reported during simulated field operation. Data were collected at various locations in the wake of a sprayer at two operating speeds (4 and 11 m s-1) at two boom heights. Ultrasonic anemometers were located directly behind the sprayer, immediately beside the sprayer tractor, and farther down the boom away from the influence of the tractor. Complex flow patterns were present behind the sprayer tractor and rear tires. An upward velocity component was measured below and downstream of the nozzles at many of the sensor locations. The magnitude of turbulence, upward velocity, and velocity deficit generally increased as the reference airspeed (travel speed combined with headwind contributions) increased. A lower boom height reduced the severity of these detrimental wake characteristics near the sprayer tractor; in general, a lower boom is known to reduce the potential of spray drift. Overall, this experimental study illustrates the variation in wake features behind a modern high-clearance sprayer under different operating conditions. Keywords: High-clearance sprayer, Spray drift, Turbulent wake, Ultrasonic anemometer.