In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the...In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.展开更多
A novel cambered surface steel tube damper(CSTD)with a cambered surface steel tube and two concave connecting plates is proposed herein.The steel tube is the main energy dissipation component and comprises a weakened ...A novel cambered surface steel tube damper(CSTD)with a cambered surface steel tube and two concave connecting plates is proposed herein.The steel tube is the main energy dissipation component and comprises a weakened segment in the middle,a transition segment,and an embedded segment.It is believed that during an earthquake,the middle weakened segment of the CSTD will be damaged,whereas the reliability of the end connection is ensured.Theoretical and experimental studies are conducted to verify the effectiveness of the proposed CSTD.Formulas for the initial stiffness and yield force of the CSTD are proposed.Subsequently,two CSTD specimens with different steel tube thicknesses are fabricated and tested under cyclic quasi-static loads.The result shows that the CSTD yields a stable hysteretic response and affords excellent energy dissipation.A parametric study is conducted to investigate the effects of the steel tube height,diameter,and thickness on the seismic performance of the CSTD.Compared with equalstiffness design steel tube dampers,the CSTD exhibits better energy dissipation performance,more stable hysteretic response,and better uniformity in plastic deformation distributions.展开更多
Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some i...Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some ingenious flapping-wing robots have been designed during the past two decades, development and application of autonomous flapping-wing robots are less successful and still require further research. Here, we report the development of a servo-driven bird-like flapping-wing robot named USTBird-I and its application in autonomous airdrop.Inspired by birds, a camber structure and a dihedral angle adjustment mechanism are introduced into the airfoil design and motion control of the wings, respectively. Computational fluid dynamics simulations and actual flight tests show that this bionic design can significantly improve the gliding performance of the robot, which is beneficial to the execution of the airdrop mission.Finally, a vision-based airdrop experiment has been successfully implemented on USTBird-I, which is the first demonstration of a bird-like flapping-wing robot conducting an outdoor airdrop mission.展开更多
基金supported by the National Key Technology R&D Program(No.2013BAD13B03)the Key R&D Project from Science and Technology Department of Zhejiang Province(Nos.2018C02026,2018C02040)+1 种基金the National Natural Science Foundation of China(No.31072246)the Fundamental Research Funds for the Central Universities(No.201564020)
文摘In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.
基金This study was funded by the National Key R&D Program of China(No.2017YFC0703600).
文摘A novel cambered surface steel tube damper(CSTD)with a cambered surface steel tube and two concave connecting plates is proposed herein.The steel tube is the main energy dissipation component and comprises a weakened segment in the middle,a transition segment,and an embedded segment.It is believed that during an earthquake,the middle weakened segment of the CSTD will be damaged,whereas the reliability of the end connection is ensured.Theoretical and experimental studies are conducted to verify the effectiveness of the proposed CSTD.Formulas for the initial stiffness and yield force of the CSTD are proposed.Subsequently,two CSTD specimens with different steel tube thicknesses are fabricated and tested under cyclic quasi-static loads.The result shows that the CSTD yields a stable hysteretic response and affords excellent energy dissipation.A parametric study is conducted to investigate the effects of the steel tube height,diameter,and thickness on the seismic performance of the CSTD.Compared with equalstiffness design steel tube dampers,the CSTD exhibits better energy dissipation performance,more stable hysteretic response,and better uniformity in plastic deformation distributions.
基金supported in part by the National Natural Science Foundation of China(62225304,61933001,61921004,62173031)the Beijing Municipal Natural Science Foundation(JQ20026)+1 种基金the Beijing Top Discipline for Artificial Intelligent Science and Engineering,University of Science and Technology Beijing。
文摘Flapping-wing flight, as the distinctive flight method retained by natural flying creatures, contains profound aerodynamic principles and brings great inspirations and encouragements to drone developers. Though some ingenious flapping-wing robots have been designed during the past two decades, development and application of autonomous flapping-wing robots are less successful and still require further research. Here, we report the development of a servo-driven bird-like flapping-wing robot named USTBird-I and its application in autonomous airdrop.Inspired by birds, a camber structure and a dihedral angle adjustment mechanism are introduced into the airfoil design and motion control of the wings, respectively. Computational fluid dynamics simulations and actual flight tests show that this bionic design can significantly improve the gliding performance of the robot, which is beneficial to the execution of the airdrop mission.Finally, a vision-based airdrop experiment has been successfully implemented on USTBird-I, which is the first demonstration of a bird-like flapping-wing robot conducting an outdoor airdrop mission.
