茶树叶片表面喷雾液滴斜撞击行为研究
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摘要
在喷雾场景中,茶树叶片具有不同倾斜方向,且会受到不同方向喷雾液滴的撞击。为掌握液滴斜撞击茶树叶片时的撞击行为及影响机理,提出了利用椭圆铺展面积来衡量斜撞击时液滴的铺展变化,并推导出包含叶片倾角和撞击角的斜撞击液滴铺展及反弹数学预测模型。为验证理论准确性,利用两台高速摄像机对喷雾液滴撞击茶树叶片的撞击过程及结果进行测试和分析。研究结果表明,撞击角、初始直径、撞击速度对粘附液滴的铺展面积影响由大到小为撞击速度、初始直径、撞击角,其中初始直径及撞击速度对液滴铺展面积有显著性影响,且是极强正相关。对于细、中液滴,撞击角对铺展面积无显著性影响;对于粗大液滴,撞击角有显著性影响,建议采用90°撞击角。茶树叶片表面具有亲水性,水滴撞击叶片表面时无反弹行为,此结果与反弹预测模型结果吻合。对液滴飞溅的影响程度由大到小为初始直径、撞击速度、撞击角。初始直径及撞击速度对液滴飞溅有显著性影响,液滴初始直径和撞击速度越大,越容易发生飞溅,撞击角对液滴飞溅无显著性影响。因茶树叶片表面比较光滑,无长绒毛,表面粗糙度较小,飞溅临界值Kcrit采用108. 4较合适。
In the spray scene,the tea tree leaves have different tilt directions which are subjected to impact by different directions of spray droplets. In order to grasp the impact behavior and influence mechanism of the droplet impact on the tea tree leaves,the elliptical spreading area was used to measure the spreading variation of the droplet during the oblique impact,and a new type of oblique impact droplet spreading and rebound mathematical prediction model,including blade inclination angle and impact angle was derived. In order to verify the theoretical accuracy,two high-speed cameras were used to test and analyze the impact process and results of spray droplets striking tea leaves. The results showed that the impact angle,initial diameter and impact velocity on the spreading area of the adherent droplets were the impact velocity,initial diameter and impact angle. The initial diameter and impact velocity had a significant effect on the droplet spread area,and were highly positively correlated. For fine and medium droplets,the impact angle had no significant effect on the spreading area; for coarse droplets,the impact angle had a significant effect,and 90° impact angle was recommended. The surface of the tea tree leaves was hydrophilic,and there was no rebound behavior when the water droplets hit the surface of the leaf.The result was consistent with the rebound prediction model. The degree of influence on the droplet splatter was the initial diameter,the impact velocity,and the impact angle. The initial diameter and impact velocity had a significant effect on droplet splatter. The larger the initial diameter and impact velocity of the droplet were,the more likely it was to splash. The impact angle had no significant effect on droplet splatter. Because the surface of tea leaves was relatively smooth,no long fluff,and the surface roughness was small,the splash threshold Kcritwas suitable to be 108. 4.
In the spray scene,the tea tree leaves have different tilt directions which are subjected to impact by different directions of spray droplets. In order to grasp the impact behavior and influence mechanism of the droplet impact on the tea tree leaves,the elliptical spreading area was used to measure the spreading variation of the droplet during the oblique impact,and a new type of oblique impact droplet spreading and rebound mathematical prediction model,including blade inclination angle and impact angle was derived. In order to verify the theoretical accuracy,two high-speed cameras were used to test and analyze the impact process and results of spray droplets striking tea leaves. The results showed that the impact angle,initial diameter and impact velocity on the spreading area of the adherent droplets were the impact velocity,initial diameter and impact angle. The initial diameter and impact velocity had a significant effect on the droplet spread area,and were highly positively correlated. For fine and medium droplets,the impact angle had no significant effect on the spreading area; for coarse droplets,the impact angle had a significant effect,and 90° impact angle was recommended. The surface of the tea tree leaves was hydrophilic,and there was no rebound behavior when the water droplets hit the surface of the leaf.The result was consistent with the rebound prediction model. The degree of influence on the droplet splatter was the initial diameter,the impact velocity,and the impact angle. The initial diameter and impact velocity had a significant effect on droplet splatter. The larger the initial diameter and impact velocity of the droplet were,the more likely it was to splash. The impact angle had no significant effect on droplet splatter. Because the surface of tea leaves was relatively smooth,no long fluff,and the surface roughness was small,the splash threshold Kcritwas suitable to be 108. 4.
引文
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[17]DAMATO T C,CARRASCO L D M,CARMONA-RIBEIRO A M,et al.The interactions between surfactants and the epicuticular wax on soybean or weed leaves:maximal crop protection with minimal wax solubilization[J].Crop Protection,2017,91:57-65.
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[20]MAO T,KUHN D C S,TRAN H.Spread and rebound of liquid droplets upon impact on flat surfaces[J].Aiche Journal,1997,43(9):2169-2179.
[21]MUNDO C,TROPEA C,SOMMERFELD M.Numerical and experimental investigation of spray characteristics in the vicinity of a rigid wall[J].Experimental Thermal&Fluid Science,1997,15(1):80-86.
[22]MUNDO C,SOMMERFELD M,TROPEA C.Droplet-wall collisions:experimental studies of the deformation and breakup process[J].International Journal of Multiphase Flow,1995,21(2):151-173.
[23]FORSTER W A.MERCER G.Process-driven models for spray droplet shatter,adhesion or bounce[C]∥9th International Symposium on Adjuvants for Agrochemicals,The Netherlands,2010.
[24]张文君.农药雾滴雾化与在玉米植株上的沉积特性研究[D].北京:中国农业大学,2014.ZHANG Wenjun.The study of pesticide droplets atomization and deposit characteristics in corn leaves[D].Beijing:China Agricultural University,2014.(in Chinese)
[25]王双双.雾化过程与棉花冠层结构对雾滴沉积的影响[D].北京:中国农业大学,2015.WANG Shuangshuang.Studying the influence of spray atomization process and cotton canopy structure on the droplet deposition[D].Beijing:China Agricultural University,2015.(in Chinese)
[26]DORR G J,FORSTER W A,MAYO L C,et al.Spray retention on whole plants:modelling,simulations and experiments[J].Crop Protection,2016,88:118-130.
[27]丁维龙,金梦杰,罗临风,等.基于虚拟模型的雾滴与叶片的交互行为分析[J].农业工程学报,2017,33(14):40-48.DING Weilong,JIN Mengjie,LUO Linfeng,et al.Behavior analysis of spray droplet interacting with plant leaves based on virtual model[J].Transactions of the CSAE,2017,33(14):40-48.(in Chinese)
[28]MASSINON M,LEBEAU F.Review of physicochemical processes involved in agrochemical spray retention[J].Biotechnologie Agronomie,Sociétéet Environnement,2013,17(3):494-504.
[29]黄晓敏,冯花,郭雅玲.茶树叶片显微结构及扫描电镜研究进展[J].福建茶叶,2011,33(5):2-4.HUANG Xiaomin,FENG Hua,GUO Yaling.Advances in microstructure and scanning electron microscopy of tea leaves[J].Tea in Fujian,2011,33(5):2-4.(in Chinese)
[2]NAIRN J J,FORSTER W A,LEEUWEN R M.‘Universal’spray droplet adhesion model-accounting for hairy leaves[J].Weed Research,2013,53(6):407-417.
[3]DORR G J,WANG S S,MAYO L C,et al.Impaction of spray droplets on leaves:influence of formulation and leaf character on shatter,bounce and adhesion[J].Experiments in Fluids,2015,56(7):1-17.
[4]DELELE M A,NUYTTENS D,DUGA A T,et al.Predicting the dynamic impact behavior of spray droplets on flat plant surfaces[J].Soft Matter,2016,12(34):7195-7211.
[5]MASSINON M,COCK N D,FORSTER W A,et al.Spray droplet impaction outcomes for different plant species and spray formulations[J].Crop Protection,2017,99:65-75.
[6]BOUKHALFA H H,MASSINON M,BELHAMRA M,et al.Contribution of spray droplet pinning fragmentation to canopy retention[J].Crop Protection,2014,56:91-97.
[7]ZWERTVAEGHER I K,VERHAEGHE M,BRUSSELMAN E,et al.The impact and retention of spray droplets on a horizontal hydrophobic surface[J].Biosystems Engineering,2014,126(39):82-91.
[8]董祥.植保机械喷头雾滴撞击植物叶面过程试验测试及仿真研究[D].北京:中国农业机械化科学研究院,2013.DONG Xiang.System aticin vestigation of 3-dimentional spray droplet impaction on leaf surfaces[D].Beijing:Chinese Academy of Agricultural Mechanization Sciences,2013.(in Chinese)
[9]DONG X,ZHU H P,YANG X J.Characterization of droplet impact and deposit formation on leaf surfaces[J].Pest Management Science,2015,71(2):302-308.
[10]贾卫东,朱和平,董祥,等.喷雾液滴撞击大豆叶片表面研究[J/OL].农业机械学报,2013,44(12):87-93.JIA Weidong,ZHU Heping,DONG Xiang,et al.Impact of spray droplet on soybean leaf surface[J/OL].Transactions of the Chinese Society for Agricultural Machinery,2013,44(12):87-93.http://www.j-csam.org/jcsam/ch/reader/view_abstract.aspx?flag=1&file_no=20131215&journal_id=jcsam.DOI:10.6041/j.issn.1000-1298.2013.12.015.(in Chinese)
[11]KWON D,HUH H K,SANG J L.Wettability and impact dynamics of water droplets on rice(Oryza sativa L.)leaves[J].Experiments in Fluids,2014,55(3):1691.
[12]AHMAD S,TANG H,YAO H.Oblique impact of two successive droplets on a flat surface[J].International Journal of Heat&Mass Transfer,2018,119:433-445.
[13]RAMAN K A,JAIMAN R K,LEE T S,et al.Dynamics of simultaneously impinging drops on a dry surface:role of impact velocity and air inertia[J].Journal of Colloid&Interface Science,2017,486(C):265-276.
[14]RAMAN K A,JAIMAN R K,LEE T S,et al.Lattice Boltzmann simulations of droplet impact onto surfaces with varying wettabilities[J].International Journal of Heat&Mass Transfer,2016,95:336-354.
[15]ABOUD D G K,ANNE-MARIE K.Splashing threshold of oblique droplet impacts on surfaces of various wettability[J].Langmuir the Acs Journal of Surfaces&Colloids,2015,31(36):10100-10111.
[16]LIN H,ZHOU H P,XU L Y,et al.Effect of surfactant concentration on the spreading properties of pesticide droplets on Eucalyptus leaves[J].Biosystems Engineering,2016,143:42-49.
[17]DAMATO T C,CARRASCO L D M,CARMONA-RIBEIRO A M,et al.The interactions between surfactants and the epicuticular wax on soybean or weed leaves:maximal crop protection with minimal wax solubilization[J].Crop Protection,2017,91:57-65.
[18]MAYO L C,MCCUE S W,MORONEY T J,et al.Simulating droplet motion on virtual leaf surfaces[J].Royal Society Open Science,2015,2(5):140528.
[19]ZHU L,GE J R,QI Y Y,et al.Droplet impingement behavior analysis on the leaf surface of Shu-ChaZao under different pesticide formulations[J].Computers&Electronics in Agriculture,2018,144:16-25.
[20]MAO T,KUHN D C S,TRAN H.Spread and rebound of liquid droplets upon impact on flat surfaces[J].Aiche Journal,1997,43(9):2169-2179.
[21]MUNDO C,TROPEA C,SOMMERFELD M.Numerical and experimental investigation of spray characteristics in the vicinity of a rigid wall[J].Experimental Thermal&Fluid Science,1997,15(1):80-86.
[22]MUNDO C,SOMMERFELD M,TROPEA C.Droplet-wall collisions:experimental studies of the deformation and breakup process[J].International Journal of Multiphase Flow,1995,21(2):151-173.
[23]FORSTER W A.MERCER G.Process-driven models for spray droplet shatter,adhesion or bounce[C]∥9th International Symposium on Adjuvants for Agrochemicals,The Netherlands,2010.
[24]张文君.农药雾滴雾化与在玉米植株上的沉积特性研究[D].北京:中国农业大学,2014.ZHANG Wenjun.The study of pesticide droplets atomization and deposit characteristics in corn leaves[D].Beijing:China Agricultural University,2014.(in Chinese)
[25]王双双.雾化过程与棉花冠层结构对雾滴沉积的影响[D].北京:中国农业大学,2015.WANG Shuangshuang.Studying the influence of spray atomization process and cotton canopy structure on the droplet deposition[D].Beijing:China Agricultural University,2015.(in Chinese)
[26]DORR G J,FORSTER W A,MAYO L C,et al.Spray retention on whole plants:modelling,simulations and experiments[J].Crop Protection,2016,88:118-130.
[27]丁维龙,金梦杰,罗临风,等.基于虚拟模型的雾滴与叶片的交互行为分析[J].农业工程学报,2017,33(14):40-48.DING Weilong,JIN Mengjie,LUO Linfeng,et al.Behavior analysis of spray droplet interacting with plant leaves based on virtual model[J].Transactions of the CSAE,2017,33(14):40-48.(in Chinese)
[28]MASSINON M,LEBEAU F.Review of physicochemical processes involved in agrochemical spray retention[J].Biotechnologie Agronomie,Sociétéet Environnement,2013,17(3):494-504.
[29]黄晓敏,冯花,郭雅玲.茶树叶片显微结构及扫描电镜研究进展[J].福建茶叶,2011,33(5):2-4.HUANG Xiaomin,FENG Hua,GUO Yaling.Advances in microstructure and scanning electron microscopy of tea leaves[J].Tea in Fujian,2011,33(5):2-4.(in Chinese)