Effect of nozzle orientation on droplet size and droplet velocity from vineyard sprays | Effet de l'orientation des buses sur la taille et la vitesse des gouttes de sprays utilisés en viticulture

Spray drift has become an important issue in pesticide application. Vineyard spraying is particularly interesting to consider, as pesticide droplets are not directed towards the ground but rather towards the targeted crop. The aim of this study was to investigate the influence of nozzle orientation on droplet size and droplet velocity using three different nozzles (IDK, TVI, and TXA) used in vineyards. Two series of measurement were performed in order to assess the effect of the gravity on sprays. Droplet size and one-dimensional droplet velocity characteristics were measured using a phase Doppler particle analyser (PDPA). Two planes, i.e., one horizontal and one vertical, were considered. Results suggest that the nozzle orientation slightly affects the size distribution, which is shifted towards larger droplets when nozzles spray horizontally compared to vertically spray. However, droplet axial velocity distribution is shifted towards lower values. Supposing that the only droplets which can reach the crop are those with an axial velocity greater than 1 m/s and a diameter larger than 100 μm, results showed significant differences according to the nozzle and orientation. More than 98.6% of the spray volume would reach the target whatever the orientation of the IDK nozzle, 78.8% of the spray volume would reach the crop when the TVI nozzle sprays horizontally, while only 16.0% of the spray volume would reach the crop when TXA nozzle sprays horizontally. This paper offers new perspectives in the comprehension and the optimization of the deposition process into the vegetation based from droplet size and velocity profiles from horizontally oriented sprays from flat fan or hollow cone nozzles.