Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to ...Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G,the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m.The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s,and the directions of the atomizer switched upward and downward in eight flights,the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G,respectively,and the latter was more stable.In addition,through analyzing the coefficients of variation(CVs)of droplet distribution,it was found that the CVs of the M-18B were 39.57%,33.54%,47.95%,and 59.04% at wind velocities of 0.9,1.1,1.4 and 4.6 m/s,respectively,gradually enhancing with the increasing of wind speed;the CVs of Thrush 510G were 79.12%,46.19%,14.90%,and 48.69% at wind velocities of 1.3,2.3,3.0 and 3.4 m/s,respectively,which displayed the irregularity maybe due to change of instantaneous wind direction.Moreover,in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath,choosing smaller CV(20%-45%)as the standard of estimation,it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B.The results provide a research foundation for promoting the development of aerial spraying in China.展开更多
Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear ...Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear hydrodynamic actions induced by the rigid body rotations and the variations of instantaneous wetted surface area were included in the second order analysis. The first order wave potentials and responses, which are sure to make the major contributions to the second order hydrodynamic actions, were obtained by employing the translating and pulsating source Green function and the Kelvin steady wave flow solution based on the linear three-dimensional hydroelasticity theory. The influences of the forward speed and the steady wave flow on the responses, and the differences of the predicted non-linear responses were illustrated by the numerical examples of a SWATH ship traveling with forward speed of 12 kn in irregular waves.展开更多
The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for...The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.展开更多
基金funded by the 863 National High-Tech R&D Program of China(Grant No.2012AA101901)National Natural Science Foundation of China(Grant No.41301471)+1 种基金China Postdoctoral Special Foundation(Grant No.2013T60189)International Postdoctoral Exchange Fellowship Program(Grant No.20130043).
文摘Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G,the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m.The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s,and the directions of the atomizer switched upward and downward in eight flights,the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G,respectively,and the latter was more stable.In addition,through analyzing the coefficients of variation(CVs)of droplet distribution,it was found that the CVs of the M-18B were 39.57%,33.54%,47.95%,and 59.04% at wind velocities of 0.9,1.1,1.4 and 4.6 m/s,respectively,gradually enhancing with the increasing of wind speed;the CVs of Thrush 510G were 79.12%,46.19%,14.90%,and 48.69% at wind velocities of 1.3,2.3,3.0 and 3.4 m/s,respectively,which displayed the irregularity maybe due to change of instantaneous wind direction.Moreover,in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath,choosing smaller CV(20%-45%)as the standard of estimation,it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B.The results provide a research foundation for promoting the development of aerial spraying in China.
文摘Based on the second order hydroelasticity theory of ships, the numerical methods and the calculated results of the non-linear hydroelastic responses of a ship traveling in rough seas were investigated. The non-linear hydrodynamic actions induced by the rigid body rotations and the variations of instantaneous wetted surface area were included in the second order analysis. The first order wave potentials and responses, which are sure to make the major contributions to the second order hydrodynamic actions, were obtained by employing the translating and pulsating source Green function and the Kelvin steady wave flow solution based on the linear three-dimensional hydroelasticity theory. The influences of the forward speed and the steady wave flow on the responses, and the differences of the predicted non-linear responses were illustrated by the numerical examples of a SWATH ship traveling with forward speed of 12 kn in irregular waves.
文摘The hydroelastic analysis and sonoelastic analysis methods are incorporated with the Green＇s function of the Pekeris ocean hydro-acoustic waveguide model to produce a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. The seabed condition is represented by a penetrable boundary of prescribed density and sound speed. This method is employed in this paper to predict the vibration and acoustic radiation of a 1 500 t Small Water Area Twin Hull （SWATH） ship in shallow sea acoustic environment. The wet resonant frequencies and radiation sound source levels are predicted and compared with the measured results of the ship in trial.
