Field and Wind Tunnel Measurements of the Airborne Spray Volume Downwind of Single Flat-Fan Nozzles

Abstract

Considerable effort is now being directed at using wind tunnel approaches to define the risk of drift from nozzle systems mounted on boom sprayers. The work reported here assesses the level of agreement that is likely to be obtained in such wind tunnel procedures through investigation using a simplified single-nozzle arrangement. The airborne spray volume 2·0 m downwind from two sizes of a single flat-fan nozzle was measured in field conditions and the results compared with those obtained from similar experiments conducted with two different wind tunnel configurations. Results from the field tests were also compared with predictions from a computer simulation model.Airborne spray volume measured downwind of the nozzles in field conditions was shown to increase approximately linearly with increasing wind speed as expected. The measurements of total drift in the wind tunnel reproduced the form of equivalent field results. Vertical profiles of airborne spray volume measured in both the field and wind tunnel experiments at nominal cross-wind speeds of 2·0 and 3·0 m/s appeared relatively insensitive to the vertical profile of the mean wind. Results from the computer simulation model also gave a reasonable description of the form of the airborne spray volume profiles, but the total quantity of drifting spray was under-predicted by the model by a factor of between two and three.