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Background <p>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 (<i>We</i>), leaf curvature (<i>C</i><sup>*</sup>), and leaf vibration frequency (<i>f</i>) on droplet impact dynamics remain insufficiently understood.</p> Results <p>By independently regulating <i>We</i>, <i>C</i><sup>*</sup>, and <i>f</i> and using high-speed imaging, we found that higher leaf curvature caused asymmetric spreading, with the maximum diameter increasing by 6.89% along the <i>x</i>-axis and decreasing by 1.95% along the <i>y</i>-axis. At high <i>We</i> (≥ 168), spreading duration was reduced by at least 35.88%, while splashing probability increased. Vibration experiments showed that droplet-leaf motion shifted from synchronous (<i>θ</i><sub><i>p</i></sub> → 0) to counter-rotating (<i>θ</i><sub><i>p</i></sub> → <i>π</i>) as <i>f</i> increased from 10 to 80&#xa0;Hz. Within the resonance range (40–50&#xa0;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 <i>We</i> and <i>f</i> as the dominant factors influencing maximum spreading (<i>P</i> &lt; 0.05; <i>We</i> &gt; <i>f</i> &gt; <i>C</i><sup>*</sup>).</p> Conclusion <p>This study clarifies the coupled roles of <i>We</i>, <i>C</i><sup>*</sup>, and <i>f</i> in droplet-leaf interactions and suggests maintaining <i>We</i> &lt; 132 in practical spraying. Under typical conditions, droplet impact velocity should be kept at 3–5&#xa0;m/s, and reduced to 2–3&#xa0;m/s for larger droplets (&gt; 500&#xa0;μm). To avoid resonance-induced splashing, airflow in air-assisted spraying should be controlled at 6–10&#xa0;m/s. These findings provide guidance for improving pesticide deposition and optimizing spray practices.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月30日

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  • Zhouming Gao,
  • Jinlong Lin,
  • Jing Ma,
  • Wei Hu,
  • Xiaoya Dong,
  • Baijing Qiu

摘要

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 (θp → 0) to counter-rotating (θp → 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.