Design And Experimental Research On Measuring Device Of Crop Leaf Drag Coefficient

Crop leaf drag coefficient is an important parameter to quantify the resistance of crop leaves.It has important guiding significance for the study of crop position and morphological information,so as to provide parameter support for the study of crop dynamics in the air and precision application technology.For a long time,there have been continuous explorations of theories,simulations and experiments around the problem of obtaining crop position and morphological information at home and abroad.However,due to the complexity of the problem,the limitations of research methods and the increasing requirements of modern agriculture for precision and efficiency This aspect has always been a key technical field for domestic and foreign scholars to conquer.At present,domestic and foreign scholars mainly focus on obtaining crop position and morphology information through sensor technology,and rarely involve the influence of external factors such as wind power on crops,and they are slightly inadequate in precision application.At the same time,domestic and foreign researches mostly focus on the position and morphological information of the whole crop,but there is no effective research plan on the movement of individual crop leaves under the action of wind.In order to effectively solve the problem of measuring the resistance coefficient of a single crop leaf,this paper refers to the current research status of drag coefficient at home and abroad,and combines the characteristics of pepper crop leaves to design a crop leaf drag coefficient measurement device based on a liquid sedimentation column.The measurement results are applied to the air using similar principles and verified by wind tunnel tests.Provide parameter support for studying the aerodynamic characteristics of crop leaves and precision application technology.The main research contents are as follows:（1）Based on the current research status of drag coefficient measurement and the characteristics of crop leaves,the research work of crop leaf drag coefficient measurement devices has been carried out.Determine the structural design scheme,power transmission mode,and motion measurement scheme of the measuring device.Some important parameters of the measuring device were measured through experiments,and a preliminary prototype was developed.（2）Using numerical simulation combined with experimental measurement to study the force curve of the rope during the measurement process,the maximum force of the rope obtained is 7.92 N and 8.25 N,respectively.Tests have verified that the loadbearing capacity of 0.8 mm nylon rope is above 10 N,so the rope will not break during the measurement.Through finite element simulation analysis,it is found that the stress on the moving mechanism during the measurement is much smaller than the allowable stress of the material.Use the simulation model of crop leaf motion to analyze the wall effect.The drag coefficient of the sphere and the disc is measured,and the measurement accuracy of the drag coefficient measuring device is preliminarily explained,so as to further measure the drag coefficient of crop leaves.（3）Using similarity theory,taking liquid measurement test as prototype test and air measurement test as model test,establish the similar relationship between prototype test and model test,that is,um ≈14.5up.The designed drag coefficient measuring device is used to carry out the prototype test,and the wall effect of the circular tube is considered.When the terminal speed is 0.59,0.61,0.65 m/s,the drag coefficients of the crop leaves in the borderless liquid are 0.342,0.327 and 0.301,respectively.A wind tunnel device was used to carry out a model test,and the drag coefficients of crop leaves in the air were measured to be 0.331,0.313 and 0.294 respectively under the same conditions.The relative error between the two is within 5%.The conversion relationship between the blade resistance coefficient in liquid and the blade resistance coefficient in air is established,and the expression is C_d,la=λ²C_d,l。...