The role of hydrodynamic effect in the meeting of multiple fish is a fascinating topic.The interactions of two self-propelled flexi-ble plates swimming in opposite directions horizontally and maintaining a certain lat...The role of hydrodynamic effect in the meeting of multiple fish is a fascinating topic.The interactions of two self-propelled flexi-ble plates swimming in opposite directions horizontally and maintaining a certain lateral distance are numerically simulated using a penalty-immersed boundary method.The effects of the flapping phase and lateral distance on the propulsive performance of two fish meetings are analyzed.Results show that,when two plates meet,if their leading edges diverge laterally,the individual plate can efficiently and rapidly move apart from the other horizontally.If their leading edges converge laterally,the plate motion can be retarded,leading to high energy consumption.Moreover,an increasing lateral distance between two plates significantly weakens the fluid-structure interactions,resulting in an exponential decline in mean cruising speed.A quantitative force analysis based on vortex dynamic theory is performed to gain physics insight into the hydrodynamic interaction mechanism.It is found that lateral separation between the two leading edges enhances the vorticity generation and boundary vorticity flux on the surface of the plate,subsequently reinforcing the thrust effect and increasing horizontal velocity.This study offers insight into the hydro-dynamic mechanisms of the fluid-structure interactions among fish moving toward each other and suggests potential strategies for enhancing the maneuverability of robotic fish in complex environment.展开更多
Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development i...Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development in China, which can be briefly divided into three periods. The first one is the early period of hardship(1971–2000). Many prototype submersibles of HOVs, ROVs, and AUVs were developed at this time, but the main achievement was the establishment of special research organizations and the training of research and development personnel. The second period can be regarded as the quick development period(2001–2015). All currently used submersibles were developed during this period. The most remarkable achievement was the successful development of 7000 m-deep manned submersible "Jiaolong." The third period aims to develop 11 000 m submersibles for challenging the full ocean depth(2016–2020). In this period, two unmanned submersibles and two manned submersibles will be the significant indicators of achievement. If this 5-year plan can be successfully completed, China can play a significant role in the investigation of the deepest part of the oceans, namely, the hadal trenches(6500–11 000 m).展开更多
This paper presents a comprehensive review and analysis of ship hull cleaning technologies.Various cleaning methods and devices applied to dry-dock cleaning and underwater cleaning are introduced in detail,including r...This paper presents a comprehensive review and analysis of ship hull cleaning technologies.Various cleaning methods and devices applied to dry-dock cleaning and underwater cleaning are introduced in detail,including rotary brushes,high-pressure and cavitation water jet technology,ultrasonic technology,and laser cleaning technology.The application of underwater robot technology in ship cleaning not only frees divers from engaging in heavy work but also creates safe and efficient industrial products.Damage to the underlying coating of the ship caused by the underwater cleaning operation can be minimized by optimizing the working process of the underwater cleaning robot.With regard to the adhesion technology mainly used in underwater robots,an overview of recent developments in permanent magnet and electromagnetic adhesion,negative pressure force adhesion,thrust force adhesion,and biologically inspired adhesion is provided.Through the analysis and comparison of current underwater robot products,this paper predicts that major changes in the application of artificial intelligence and multirobot cooperation,as well as optimization and combination of various technologies in underwater cleaning robots,could be expected to further lead to breakthroughs in developing next-generation robots for underwater cleaning.展开更多
As autonomous underwater vehicles(AUVs)merely adopt the inductive obstacle avoidance mechanism to avoid collisions with underwater obstacles,path planners for underwater robots should consider the poor search efficien...As autonomous underwater vehicles(AUVs)merely adopt the inductive obstacle avoidance mechanism to avoid collisions with underwater obstacles,path planners for underwater robots should consider the poor search efficiency and inadequate collision-avoidance ability.To overcome these problems,a specific two-player path planner based on an improved algorithm is designed.First,by combing the artificial attractive field(AAF)of artificial potential field(APF)approach with the random rapidly exploring tree(RRT)algorithm,an improved AAF-RRT algorithm with a changing attractive force proportional to the Euler distance between the point to be extended and the goal point is proposed.Second,a twolayer path planner is designed with path smoothing,which combines global planning and local planning.Finally,as verified by the simulations,the improved AAF-RRT algorithm has the strongest searching ability and the ability to cross the narrow passage among the studied three algorithms,which are the basic RRT algorithm,the common AAF-RRT algorithm,and the improved AAF-RRT algorithm.Moreover,the two-layer path planner can plan a global and optimal path for AUVs if a sudden obstacle is added to the simulation environment.展开更多
Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numeri...Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numerical wave tanks suffer from issues known as the numerical dissipation and numerical dispersion. The former causes wave energy to be slowly dissipated and the latter shifts wave frequencies during wave propagation. This paper proposes a simple method of depressing numerical dissipation effects on the basis of solving Euler equations using the finite difference method(FDM). The wave propagation solutions are solved analytically taking into account the influence of the damping terms. The main idea of the method is to append a source term to the momentum equation, whose strength is determined by how strong the numerical damping effect is. The method is verified by successfully depressing numerical effects during the simulation of regular linear waves, Stokes waves and irregular waves. By applying the method, wave energy is able to be close to its initial value after long distance of travel.展开更多
The title of the article“Buckling of Multiple Intersecting Spherical Shells Under Uniform External Pressure,”written by Zhang,J.,Li,S.,Cui,W.et al.,was spelled incorrectly.The original article has been corrected.
This study explored the buckling of multiple intersecting spherical shells.A three-segment spherical shell was designed using the theory of deformation coordination;the design was compared with that of a volume-equiva...This study explored the buckling of multiple intersecting spherical shells.A three-segment spherical shell was designed using the theory of deformation coordination;the design was compared with that of a volume-equivalent cylindrical shell and ring-ribbed cylindrical shell.The numerical results indicated that the buckling capacity of the three-segment spherical shell was superior to those of the other two cylindrical shells.To validate our numerical approach,three laboratory-scale shell models were fabricated.Each model was accurately measured and slowly tested in a pressure chamber;thus,the tested shells were studied numerically.The experimental collapse modes agreed well with numerical results,and the collapse load of the three-segment pressure shell was considerably higher than that of the two cylindrical shells.展开更多
Soft pneumatic actuators(SPAs)have attracted enormous attention in the growing field of robotics.Among different SPAs,composite reinforced actuators(CRAs)are widely used because of their simple structure and high cont...Soft pneumatic actuators(SPAs)have attracted enormous attention in the growing field of robotics.Among different SPAs,composite reinforced actuators(CRAs)are widely used because of their simple structure and high controllability.However,multistep molding,a time-consuming method,is still the predominant fabrication method.Here,we propose a multimaterial embedded printing method(ME3P)to fabricate CRAs.In comparison with other 3-dimensional printing methods,our method improves fabrication flexibility greatly.Via the design and fabrication of the reinforced composites’patterns and different geometries of the soft body,we demonstrate actuators with programmable responses(elongation,contraction,twisting,bending,and helical and omnidirectional bending).Finite element analysis is employed for the prediction of pneumatic responses and the inverse design of actuators based on specific actuation needs.Lastly,we use tube-crawling robots as a model system to demonstrate our ability to fabricate complex soft robots for practical applications.This work demonstrates the versatility of ME3P for the future manufacturing of CRA-based soft robots.展开更多
For the design and operation of a floating bridge,the understanding of its hydroelastic behavior in waves is of great importance.This paper investigated the hydroelastic performances of a ribbon bridge under wave acti...For the design and operation of a floating bridge,the understanding of its hydroelastic behavior in waves is of great importance.This paper investigated the hydroelastic performances of a ribbon bridge under wave action.A brief introduction on the estimation of dynamic responses of the floating bridge and the comparisons between the experiments and estimation were presented.Based on the 3D hydroelasticity theory,the hydroelastic behavior of the ribbon bridge modeled by finite element method(FEM)was analyzed by employing the mode superposition method.And the relevant comparisons between the numerical results and experimental data obtained from one tenth scale elastic model test in the ocean basin were made.It is found that the present method is applicable and adaptable for predicting the hydroelastic response of the floating bridge in waves.展开更多
With the continuous deepening of ocean exploration,submersibles have become essential tools that have garnered considerable attention in the academia.As of the 2020s,driven by advancements in materials and various dis...With the continuous deepening of ocean exploration,submersibles have become essential tools that have garnered considerable attention in the academia.As of the 2020s,driven by advancements in materials and various disciplines,the development of submersibles has undergone important transformations compared to their initial state.In this paper,we provide a comprehensive review of the developments in submersible technology from a historical point of view.In particular,we emphasize the emergence of the robotic fish-type submersibles.This process is characterized by the fusion of biomimicry and advanced technologies,and represents the future direction of submersible developments.Thus,we also emphasize the key technological challenges that robotic fish-type submersibles should focus on.Finally,we outline a general procedure for developing biomimetic robotic fish-type submersibles by drawing insights from a recent 2,000-m biomimicry prototype study.We hope to pave a smoother path for the future advancement of submersibles.展开更多
We report self-organized periodic nanostructures on amorphous silicon thin flms by femtosecond laser-induced oxidation.The dependence of structural periodicity on the thickness of silicon flms and the substrate materi...We report self-organized periodic nanostructures on amorphous silicon thin flms by femtosecond laser-induced oxidation.The dependence of structural periodicity on the thickness of silicon flms and the substrate materials is investigated.The results reveal that when silicon flm is 200 nm,the period of self-organized nanostructures is close to the laser wavelength and is insensitive to the substrates.In contrast,when the silicon flm is 50 nm,the period of nanostructures is much shorter than the laser wavelength,and is dependent on the substrates.Furthermore,we demonstrate that,for the thick silicon flms,quasi-cylindrical waves dominate the formation of periodic nanostructures,while for the thin silicon flms,the formation originates from slab waveguide modes.Finite-diference time-domain method-based numerical simulations support the experimental discoveries.展开更多
The processes and phenomena hidden in massive marine data importantly impact heat transportation,material transportation,and climate formation.Visualization can assist people in mining and understanding marine data to...The processes and phenomena hidden in massive marine data importantly impact heat transportation,material transportation,and climate formation.Visualization can assist people in mining and understanding marine data to gain insight.Thus,oceanographers must study ocean processes and phenomena.However,one remaining challenge in the existing visualization methods is efficiently rendering marine data with large volumes and illustrating the internal structure of marine phenomena.To solve this problem,we propose a new visual analytics framework involving 4 parts for visualizing extensive marine scalar volume data.We first use a single box and double spheres separately as proxy geometries to draw a flat Earth and spherical Earth.Second,we design a new ray-casting algorithm based on graphics processing unit to reduce the volume of marine data.This algorithm accelerates volume rendering by using an adaptive texture sampling rate and step size.Third,we use a depth correction algorithm to accurately restore the ocean scale.Finally,we develop an internal roaming algorithm to observe the internal structure of marine data.In this way,users can dynamically observe the internal structure of marine phenomena.To illustrate the effectiveness of our algorithms,we use them to visualize Hybrid Coordinate Ocean Model data and Argo data.展开更多
基金joined PI of Westlake University(Grant Nos.041030150118 and 103110556022101)Scientific Research Funding Project of Westlake University(Grant No.2021WUFP017).
文摘The role of hydrodynamic effect in the meeting of multiple fish is a fascinating topic.The interactions of two self-propelled flexi-ble plates swimming in opposite directions horizontally and maintaining a certain lateral distance are numerically simulated using a penalty-immersed boundary method.The effects of the flapping phase and lateral distance on the propulsive performance of two fish meetings are analyzed.Results show that,when two plates meet,if their leading edges diverge laterally,the individual plate can efficiently and rapidly move apart from the other horizontally.If their leading edges converge laterally,the plate motion can be retarded,leading to high energy consumption.Moreover,an increasing lateral distance between two plates significantly weakens the fluid-structure interactions,resulting in an exponential decline in mean cruising speed.A quantitative force analysis based on vortex dynamic theory is performed to gain physics insight into the hydrodynamic interaction mechanism.It is found that lateral separation between the two leading edges enhances the vorticity generation and boundary vorticity flux on the surface of the plate,subsequently reinforcing the thrust effect and increasing horizontal velocity.This study offers insight into the hydro-dynamic mechanisms of the fluid-structure interactions among fish moving toward each other and suggests potential strategies for enhancing the maneuverability of robotic fish in complex environment.
基金supported by the State Key Program of National Natural Science of China "Structural Reliability Analysis on the Spherical Hull of Deep Sea MSs"(Grant No.51439004)the Scientific Innovation Program Project of "Key technology research and experimental validation of deep MS" by the Shanghai Committee of Science and Technology(Grant No.15DZ1207000)
文摘Given the recent success in the development of several submersibles in China, people's interest in the history of submersible development is increasing. This paper presents the history of submersible development in China, which can be briefly divided into three periods. The first one is the early period of hardship(1971–2000). Many prototype submersibles of HOVs, ROVs, and AUVs were developed at this time, but the main achievement was the establishment of special research organizations and the training of research and development personnel. The second period can be regarded as the quick development period(2001–2015). All currently used submersibles were developed during this period. The most remarkable achievement was the successful development of 7000 m-deep manned submersible "Jiaolong." The third period aims to develop 11 000 m submersibles for challenging the full ocean depth(2016–2020). In this period, two unmanned submersibles and two manned submersibles will be the significant indicators of achievement. If this 5-year plan can be successfully completed, China can play a significant role in the investigation of the deepest part of the oceans, namely, the hadal trenches(6500–11 000 m).
基金Supported by the General Program of the National Natural Science Foundation of China under Grant No.51879157the“Construction of a Leading Innovation Team”project by the Hangzhou Municipal Governmentthe Startup Funding of Newjoined PI of Westlake University under Grant No.041030150118。
文摘This paper presents a comprehensive review and analysis of ship hull cleaning technologies.Various cleaning methods and devices applied to dry-dock cleaning and underwater cleaning are introduced in detail,including rotary brushes,high-pressure and cavitation water jet technology,ultrasonic technology,and laser cleaning technology.The application of underwater robot technology in ship cleaning not only frees divers from engaging in heavy work but also creates safe and efficient industrial products.Damage to the underlying coating of the ship caused by the underwater cleaning operation can be minimized by optimizing the working process of the underwater cleaning robot.With regard to the adhesion technology mainly used in underwater robots,an overview of recent developments in permanent magnet and electromagnetic adhesion,negative pressure force adhesion,thrust force adhesion,and biologically inspired adhesion is provided.Through the analysis and comparison of current underwater robot products,this paper predicts that major changes in the application of artificial intelligence and multirobot cooperation,as well as optimization and combination of various technologies in underwater cleaning robots,could be expected to further lead to breakthroughs in developing next-generation robots for underwater cleaning.
基金Supported by Zhejiang Key R&D Program 558 No.2021C03157the“Construction of a Leading Innovation Team”project by the Hangzhou Munic-559 ipal government,the Startup funding of New-joined PI of Westlake University with Grant No.560(041030150118)the funding support from the Westlake University and Bright Dream Joint In-561 stitute for Intelligent Robotics.
文摘As autonomous underwater vehicles(AUVs)merely adopt the inductive obstacle avoidance mechanism to avoid collisions with underwater obstacles,path planners for underwater robots should consider the poor search efficiency and inadequate collision-avoidance ability.To overcome these problems,a specific two-player path planner based on an improved algorithm is designed.First,by combing the artificial attractive field(AAF)of artificial potential field(APF)approach with the random rapidly exploring tree(RRT)algorithm,an improved AAF-RRT algorithm with a changing attractive force proportional to the Euler distance between the point to be extended and the goal point is proposed.Second,a twolayer path planner is designed with path smoothing,which combines global planning and local planning.Finally,as verified by the simulations,the improved AAF-RRT algorithm has the strongest searching ability and the ability to cross the narrow passage among the studied three algorithms,which are the basic RRT algorithm,the common AAF-RRT algorithm,and the improved AAF-RRT algorithm.Moreover,the two-layer path planner can plan a global and optimal path for AUVs if a sudden obstacle is added to the simulation environment.
基金The National Natural Science Foundation of China under contract No.51609101 and 51909103the Natural Science Foundation of Fujian Province of China under contract Nos 2017J01701,2017J05085 and 2018J05090the Outstanding Young University Scientific Research Talents Cultivation Plan of Fujian Province of China
文摘Numerical wave tanks are widely-acknowledged tools in studying waves and wave-structure interactions. They can generate waves under realistic scales and offers more information on the fluid field. However, most numerical wave tanks suffer from issues known as the numerical dissipation and numerical dispersion. The former causes wave energy to be slowly dissipated and the latter shifts wave frequencies during wave propagation. This paper proposes a simple method of depressing numerical dissipation effects on the basis of solving Euler equations using the finite difference method(FDM). The wave propagation solutions are solved analytically taking into account the influence of the damping terms. The main idea of the method is to append a source term to the momentum equation, whose strength is determined by how strong the numerical damping effect is. The method is verified by successfully depressing numerical effects during the simulation of regular linear waves, Stokes waves and irregular waves. By applying the method, wave energy is able to be close to its initial value after long distance of travel.
文摘The title of the article“Buckling of Multiple Intersecting Spherical Shells Under Uniform External Pressure,”written by Zhang,J.,Li,S.,Cui,W.et al.,was spelled incorrectly.The original article has been corrected.
基金This study was supported by the National Natural Science Foundation of China(Grant numbers 51709132 and 51679133),Jiangsu Provincial Government Scholarship Programme,and the“Construction of a Leading Innovation Team”project by Hangzhou City Government.
文摘This study explored the buckling of multiple intersecting spherical shells.A three-segment spherical shell was designed using the theory of deformation coordination;the design was compared with that of a volume-equivalent cylindrical shell and ring-ribbed cylindrical shell.The numerical results indicated that the buckling capacity of the three-segment spherical shell was superior to those of the other two cylindrical shells.To validate our numerical approach,three laboratory-scale shell models were fabricated.Each model was accurately measured and slowly tested in a pressure chamber;thus,the tested shells were studied numerically.The experimental collapse modes agreed well with numerical results,and the collapse load of the three-segment pressure shell was considerably higher than that of the two cylindrical shells.
基金The authors are grateful for the financial support for this research by the Zhejiang Provincial Key R&D Program of China(2021C03157)the National Natural Science Foundation of China(No.51905446)+2 种基金Guangdong Provincial Key R&D Program of 2021 Ocean Six Industrial Project(2021-45)Scientific Research Funding Project of Westlake University(2021WUFP017)the Startup funding of New-joined PI of Westlake University(041030150118)。
文摘Soft pneumatic actuators(SPAs)have attracted enormous attention in the growing field of robotics.Among different SPAs,composite reinforced actuators(CRAs)are widely used because of their simple structure and high controllability.However,multistep molding,a time-consuming method,is still the predominant fabrication method.Here,we propose a multimaterial embedded printing method(ME3P)to fabricate CRAs.In comparison with other 3-dimensional printing methods,our method improves fabrication flexibility greatly.Via the design and fabrication of the reinforced composites’patterns and different geometries of the soft body,we demonstrate actuators with programmable responses(elongation,contraction,twisting,bending,and helical and omnidirectional bending).Finite element analysis is employed for the prediction of pneumatic responses and the inverse design of actuators based on specific actuation needs.Lastly,we use tube-crawling robots as a model system to demonstrate our ability to fabricate complex soft robots for practical applications.This work demonstrates the versatility of ME3P for the future manufacturing of CRA-based soft robots.
基金This project was supported by the Commission of Science,Technology and Industry for National Defense.
文摘For the design and operation of a floating bridge,the understanding of its hydroelastic behavior in waves is of great importance.This paper investigated the hydroelastic performances of a ribbon bridge under wave action.A brief introduction on the estimation of dynamic responses of the floating bridge and the comparisons between the experiments and estimation were presented.Based on the 3D hydroelasticity theory,the hydroelastic behavior of the ribbon bridge modeled by finite element method(FEM)was analyzed by employing the mode superposition method.And the relevant comparisons between the numerical results and experimental data obtained from one tenth scale elastic model test in the ocean basin were made.It is found that the present method is applicable and adaptable for predicting the hydroelastic response of the floating bridge in waves.
基金funded by the National Key Research and Development Program of China(2022YFC2805200)startup funding from Westlake University(041030150118)the Scientific Research Funding Project of Westlake University(2021WUFP017).
文摘With the continuous deepening of ocean exploration,submersibles have become essential tools that have garnered considerable attention in the academia.As of the 2020s,driven by advancements in materials and various disciplines,the development of submersibles has undergone important transformations compared to their initial state.In this paper,we provide a comprehensive review of the developments in submersible technology from a historical point of view.In particular,we emphasize the emergence of the robotic fish-type submersibles.This process is characterized by the fusion of biomimicry and advanced technologies,and represents the future direction of submersible developments.Thus,we also emphasize the key technological challenges that robotic fish-type submersibles should focus on.Finally,we outline a general procedure for developing biomimetic robotic fish-type submersibles by drawing insights from a recent 2,000-m biomimicry prototype study.We hope to pave a smoother path for the future advancement of submersibles.
基金supported by the National Natural Science Foundation of China(Grant Nos.12004314 and 62105269)LPS was supported by the Open Project Program of the Wuhan National Laboratory for Optoelectronics(No.2020WNLOKF004)the Zhejiang Provincial Natural Science Foundation of China(No.Q21A040010).
文摘We report self-organized periodic nanostructures on amorphous silicon thin flms by femtosecond laser-induced oxidation.The dependence of structural periodicity on the thickness of silicon flms and the substrate materials is investigated.The results reveal that when silicon flm is 200 nm,the period of self-organized nanostructures is close to the laser wavelength and is insensitive to the substrates.In contrast,when the silicon flm is 50 nm,the period of nanostructures is much shorter than the laser wavelength,and is dependent on the substrates.Furthermore,we demonstrate that,for the thick silicon flms,quasi-cylindrical waves dominate the formation of periodic nanostructures,while for the thin silicon flms,the formation originates from slab waveguide modes.Finite-diference time-domain method-based numerical simulations support the experimental discoveries.
文摘The processes and phenomena hidden in massive marine data importantly impact heat transportation,material transportation,and climate formation.Visualization can assist people in mining and understanding marine data to gain insight.Thus,oceanographers must study ocean processes and phenomena.However,one remaining challenge in the existing visualization methods is efficiently rendering marine data with large volumes and illustrating the internal structure of marine phenomena.To solve this problem,we propose a new visual analytics framework involving 4 parts for visualizing extensive marine scalar volume data.We first use a single box and double spheres separately as proxy geometries to draw a flat Earth and spherical Earth.Second,we design a new ray-casting algorithm based on graphics processing unit to reduce the volume of marine data.This algorithm accelerates volume rendering by using an adaptive texture sampling rate and step size.Third,we use a depth correction algorithm to accurately restore the ocean scale.Finally,we develop an internal roaming algorithm to observe the internal structure of marine data.In this way,users can dynamically observe the internal structure of marine phenomena.To illustrate the effectiveness of our algorithms,we use them to visualize Hybrid Coordinate Ocean Model data and Argo data.
