采用双向流固耦合方法构建辅助气流作用下棉花叶片变形模型  

Deformation modelling of cotton leaf under assisted airflow using bidirectional fluid-structure coupling method

作　　者：刘兴华[1,2] 苑进 李扬[1,3] 索金政 刘雪美[1,2] Liu Xinghua;Yuan Jin;Li Yang;Suo Jinzheng;Liu Xuemei(College of Mechanical and Electronic Engineering,Shandong Agricultural University,Tai’an 271018,China;Shandong Provincial Engineering Laboratory of Agricultural Equipment Intelligence,Tai’an 271018,China;Shandong Provincial Key Laboratory of Horticultural Machinery and Equipment,Tai’an 271018,China)

机构地区：[1]山东农业大学机械与电子工程学院,泰安271018 [2]山东省农业装备智能化工程实验室,泰安271018 [3]山东省园艺机械与装备重点实验室,泰安271018

出　　处：《农业工程学报》2021年第5期68-76,共9页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(52075308);山东省自然科学基金项目(ZR2019PC024);山东省农业重大应用技术创新项目(SD2019NJ003)。

摘　　要：气流辅助喷雾中,辅助气流能够使冠层叶片变形、拓宽雾滴输运通道,有助于提高雾滴在作物冠层内沉积均匀性。为进一步研究辅助气流作用下叶片变形机理,以棉花叶片为研究对象,首先,在测定叶片力学参数的基础上,建立了棉花叶片双向流固耦合模型,并利用高速摄像技术验证了模型的有效性;进一步,借助耦合模型,以辅助气流风速、叶倾角、叶柄及叶面弹性模量为试验因素,以叶柄和叶面挠度值为评价指标,开展正交试验分析,得出试验因素影响叶片变形的显著性顺序依次为:气流速度、弹性模量、叶倾角;最后,基于非线性最小二乘法构建棉花叶片变形的参数辨识模型,所建的叶柄挠曲线方程的平均绝对百分比误差(Mean Absolute Percentage Error,MAPE)为5.13%,叶面主叶脉挠曲线方程的MAPE为10.43%,证明了叶片变形数学模型的有效性。依据建立的叶片变形模型,量化分析了不同风速与初始叶倾角参数组合下叶片迎风面积的动态变化过程,揭示了速度不恰当的辅助气流作用下冠层郁闭度增加的原因,明确了初始叶倾角为20°和30°时,棉花叶片的辅助气流末速度应分别不小于2.4和2.9m/s。本研究为理解辅助气流喷雾中作物冠层郁闭度的动态变化、合理选取施药工作参数提供参考。Assisted airflow can cause the deformation of canopy leaf for the wide transport channel of droplets in the air-assisted spray.The uniformity of droplet deposition can be enhanced in the crop canopy.In this study,a mathematical model of cotton leaf deformation was established under the action of assisted airflow using fluid-structure coupling and parameter identification.Firstly,the petiole and leaf surface samples of cotton were collected to obtain the size parameters.A three-point bending was selected to calculate the elastic modulus of petiole and leaf surface.The moisture content of the petiole and leaf surface was measured during drying at 105℃.The results showed that the median elastic modulus of leaf surface was 46.5 MPa,where 95%confidence interval was[28.5,64.5]MPa,whereas the median elastic modulus of petiole was 244.6 MPa,where 95%confidence interval was[215.5,273.69]MPa,while the average moisture content of petiole was 87.2%,where 95%confidence interval was[82.5%,91.9%],and the average moisture content of leaf surface was 80.7%,where 95%confidence interval was[72.3%,89.1%].Then,a bidirectional fluid-structure coupling model was established to characterize the deformation process of cotton leaf.The deflection data were obtained in four monitoring points,including the middle and end of the petiole,as well as the center and tip of leaf surface.A high-speed camera was used to carry out the deformation test of cotton leaf with assisted airflow.The deflection test data of monitoring points were captured to verify the coupling model with the maximum simulation error of 9.85%.Furthermore,an orthogonal test was performed on experimental factors,including the assisted airflow speed,leaf inclination angle,elastic moduli of petiole and leaf.A significant order of experimental factors was obtained:wind speed,elastic modulus,leaf inclination angle.Finally,a mathematical model of cotton leaf deformation was constructed using the nonlinear least square.A trust-region iterative was used to obtain the identification

关 键 词：辅助气流 模型 叶片变形 流固耦合 参数辨识 

分 类 号：TP391.9[自动化与计算机技术—计算机应用技术]