Comparative analysis of micro-physical characteristics of sprayed droplets using various measurement technologies

The study of the micro-physical characteristics of spray droplets provides crucial insights into the impact of sprinkler water on soil erosion, leaf impact, and the microclimate of agricultural environments. However, the variability in measurement outcomes across different technologies due to their distinct measurement principles is a significant challenge. This research aims to evaluate and compare the droplet diameter, velocity, application rate, and kinetic energy rate using four distinct measurement technologies: the paper stain method (PS), flour pellet method (FP), laser precipitation monitor (LPM), and two-dimensional video disdrometer (2DVD), alongside a rain gauge (RG) in the context of sprinkler irrigation conditions. The results reveal that: (1) The FP method struggled to capture small droplets under the same spray conditions, while the PS method recorded a maximum droplet diameter exceeding 7 mm. The LPM registered the highest droplet count per unit area and time, notably capturing a significant number of small droplets (< 1 mm). Conversely, the 2DVD provided a more uniform distribution of droplet sizes, with the LPM’s mean equivalent droplet diameter (dv) being 0.86 times that of the 2DVD. (2) Although droplet diameters and velocities measured by the 2DVD, LPM, FP, and PS, decreased with increased working pressure, these technologies concurred when assessing low-velocity and small-diameter droplet. (3) The 2DVD’s larger sampling area compared to other methods enables the acquisition of more representative droplet characteristics, including their irregular shapes, suggesting its utility in measuring the micro-physical properties of sprayed droplets. (4) Based on the kinetic energy rate measured by the 2DVD under identical conditions, kinetic energy rate calibration factors of 0.88, 1.15, and 1.10 are suggested for the LPM, FP, and PS, respectively. This study provides essential data for calibrating and applying various droplet measurement technologies.