Use of the Logistic Function to Model Cumulative Volumes of Spray Nozzles

Modeling spray drop size distribution helps a proper nozzle selection in order to reduce the impact of pesticides on the environment during phytosanitary treatments. In fact, drop size is recognized as the most important factor that affects all aspects of a pesticide application: biological efficacy, environmental pollution, and operator exposure. This research represents a preliminary study in using the logistic function to fit the cumulative volume curves of a spray. Its S-shaped form may be useful in describing in simple manner the cumulative volume curves and then the pulverization capabilities of a nozzle. Experimental tests were carried out with an Albuz (France) orange hollow cone nozzle ATR 80 (European color code) at four pressures: 300, 500, 1000, and 1500 kPa. Drop size was measured by exploiting the liquid immersion method in a custom-made test-bench. Preliminary results showed that the proposed model, when used on a validation dataset, fitted the experimental data with high correlation coefficient (on average 0.9992) and low percentage of bias values, tending to improve when the pressure increased (decreasing from +3.69 % to -0.08 % when the pressure increased from 300 to 1500 kPa).