液滴在柔性辣椒叶片表面撞击行为研究

Impact Behavior of Droplets on Surface of Flexible Chili Leaves

液滴撞击叶片时会使叶片发生弯曲变形,这种变形会对液滴的撞击行为产生影响。基于前人液滴撞击刚性表面的理论模型,探究了液滴撞击柔性辣椒叶片时叶片弹性系数对液滴撞击行为的影响,考虑叶片弹性势能、液滴和叶片重力势能,建立了液滴撞击柔性辣椒叶片最大扩散因子数学预测模型。以液滴粒径、撞击速度、撞击点到叶尖距离占比为试验因素,对数学模型进行了合理性验证。结果表明:3个因素对液滴粘附和飞溅均有显著性影响(P<0.05)。数学模型对液滴撞击柔性辣椒叶片最大扩散因子预测误差在10%以内,但此误差会随着叶片弹性系数的增加而减小。液滴撞击柔性辣椒叶片没有发生反弹,和理论模型预测结果一致。液滴粘附时,叶片弹性系数与液滴达到最大扩散的时间呈负相关,与撞击刚性固定叶片相比,达到最大扩散的时间增加量在0.5 ms以内,最大扩散因子减小率在25%以内,传递给叶片弹性势能占初始总能量的比随着叶片弹性系数的增加呈现先减小后增大趋势。液滴飞溅时,在到叶尖距离占比的20%、40%、60%、80%处,与刚性叶片相比,飞溅临界值Kcrit分别增加16.202%、10.515%、6.508%、4.467%,说明叶片越靠近弹性系数小的区域,液滴越不容易飞溅。本文为液滴在柔性植物叶片上的撞击行为研究和喷雾参数选择提供了一种方法。

Droplets will cause the blade to bend and deform when impacting the blade,and this deformation will affect the droplet impact behavior.Based on the previous theoretical model of droplet impact on rigid surfaces,the influence of blade elasticity coefficient on droplet impact behavior when droplet impacted on flexible chili blades was investigated,and the mathematical prediction model of the maximum diffusion factor of droplet impact on flexible chili leaves was established by taking into account the elastic potential energy of blades,and the gravitational potential energy of droplets and blades.The reasonableness of the mathematical model was verified with droplet particle size,impact velocity,and the percentage of the distance from the impact point to the leaf tip as experimental variables.The results showed that all three factors had a significant effect on droplet adhesion and splashing(P<0.05).The prediction error of the mathematical model for the maximum diffusion factor of droplet impact on flexible chili leaves was within 10%.When the droplet impacted the flexible chili blade without rebound consistent with theoretical model predictions and the droplet adheres,the size of the blade’s elastic coefficient was negatively correlated with the time for the droplet to reach the maximum diffusion,and compared with the impact on the rigid fixed blade,the increase in time to reach the maximum diffusion was within 0.5 ms,and the reduction rate of the maximum diffusion factor was within 25%,and the ratio of elastic potential energy to the total initial energy transferred to the blade showed a trend of decreasing and then increasing with the increase in the blade elasticity coefficient,which showed a tendency to decrease first and then increase.When the droplet splashed at 20%,40%,60%,80%of the distance to the leaf tip,the splash critical value Kcrit was increased by 16.202%,10.515%,6.508%,4.467%,respectively,compared with the splash value of the rigid blade,which indicated that the closer the leaf was to the region where the blade elasticity coefficient was small,the droplet would be less likely to splash.The research result can provide a method for the study of droplet impact behavior on flexible plant leaves and spray parameter selection.