Experimental Study On The Aerodynamic Characteristics Of Paper Mulberry Leaves

The study is about reconfiguration and vibration of single paper mulberry leaf which is vertically hanging to the flow in the 0²5m/s wind.It need to take the shapes of the laminae and the windward surface into account.The laminae are very large mittens with one or two lobes looking like left or right thumbs,double thumbs or no thumbs.They were front or back surface facing wind.The experiments mainly include the force balance test,high-speed camera capturing the changes leaves states and the elastic modulus of the petiole test.The main method of data analysis is statistical.The following conclusions are obtained through a large number of experiments:With the increasing of wind speed,there are several reconfigurations and several vibration at the given speeds.There are three types of lamina steady status of the whole,i.e,wing shape,conical shape,thin delta wing,and three main ways of rolling up,i.e,U,?and?type.The reconfiguration would greatly reduce the size of the windward surface of the leaves,especially the width,and the average width is 0.21 to the beginning in 25m/s.The vibrations are mainly caused by the petiole,and the edge and tip of blade vibrate,too.The vibration frequency of the petiole is several to tens Hertz.The back has better aerodynamic performance.The leaf angle and yaw angle are close to 0°with the increasing of wind speed.The relationship between drag and wind speed is affected by vibration and stability,and the performance of reconfiguration is excellent in reducing drag,but the vibration will increase the drag coefficient.The drag coefficient is close to 0.05 with the increasing of wind speed.Elastic modulus of Paper mulberry petiole is 154MPa.The average bending stiffness of paper mulberry leave is 7.46×10^-7N?m².The critical wind speed of vibration is a function of the elastic modulus of petiole,the length of petiole,and the real-time width of laminae.