Experimental investigation of droplet impact behavior considering leaf curvature and vibration effects

Abstract Background The impact behavior of droplets on crop leaves is a key factor in evaluating pesticide spray effectiveness. However, the coupled influences of the Weber number ( We ), leaf curvature ( C * ), and leaf vibration frequency ( f ) on droplet impact dynamics remain insufficiently understood. Results By independently regulating We , C * , and f and using high-speed imaging, we found that higher leaf curvature caused asymmetric spreading, with the maximum diameter increasing by 6.89% along the x -axis and decreasing by 1.95% along the y -axis. At high We (≥ 168), spreading duration was reduced by at least 35.88%, while splashing probability increased. Vibration experiments showed that droplet-leaf motion shifted from synchronous ( θ p → 0) to counter-rotating ( θ p → π ) as f increased from 10 to 80 Hz. Within the resonance range (40–50 Hz), both spreading and amplitude reached peak values, accompanied by the highest splashing risk. A quadratic regression model developed from a three-factor orthogonal design identified We and f as the dominant factors influencing maximum spreading ( P < 0.05; We > f > C * ). Conclusion This study clarifies the coupled roles of We , C * , and f in droplet-leaf interactions and suggests maintaining We < 132 in practical spraying. Under typical conditions, droplet impact velocity should be kept at 3–5 m/s, and reduced to 2–3 m/s for larger droplets (> 500 μm). To avoid resonance-induced splashing, airflow in air-assisted spraying should be controlled at 6–10 m/s. These findings provide guidance for improving pesticide deposition and optimizing spray practices.