This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near th...This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near the separation vortex region.Three distinct motion modes are identified:periodic rotation or oscillation within the vortex(trapping),downstream transport(escape),and transition state exhibiting unstable trapping.A dynamic balance among inward migration,centrifugal effects,wall interactions,and elastic forces enables the particle to achieve stable orbital motion within two distinct limit cycles.The topology of these orbits is governed by parameters,including the aspect ratio,structural flexibility,deformation intensity,and fluid inertia,all of which are characterized by the Reynolds number(Re).Specifically,fluid inertia plays a dominant role in facilitating particle trapping.At a fixed Re,a particle with a smaller aspect ratio tends to migrate inward and become trapped,whereas one with a larger aspect ratio is more likely to escape.Structural flexibility,especially when enhanced by confinement near the wall,leads to elastic deformation that induces secondary vortices and a weak flipping motion.The deformation intensityαsignificantly influences the lateral migration of the slender particle after the initial release;a largerαcauses it to drift toward the channel centerline,increasing the probability of escape.These findings provide a theoretical foundation for optimizing the transport and capture of slender soft swimmers in complex flow environments.展开更多
Ferroptosis is a newly proposed type of programmed cell death,which has been associated with a variety of diseases including tumors.Researchers have thereby presented nanoplatforms to mediate ferroptosis for anti-canc...Ferroptosis is a newly proposed type of programmed cell death,which has been associated with a variety of diseases including tumors.Researchers have thereby presented nanoplatforms to mediate ferroptosis for anti-cancer therapy.However,the development of ferroptosis-based nanotherapeutics is generally hindered by the limited penetration depth in tumors,poor active pharmaceutical ingredient(API)loading content and the systemic toxicity.Herein,self-propelled ferroptosis nanoinducers composed of two endogenous proteins,glucose oxidase and ferritin,are presented to show enhanced tumor inhibition via ferroptosis while maintaining high API and biocompatibility.The accumulation of our proteomotors at tumor regions is facilitated by the active tumor-targeting effect of ferritin.The enhanced diffusion of proteomotors is then actuated by efficiently decomposing glucose into gluconic acid and H_(2)O_(2),leading to deeper penetration and enhanced uptake into tumors.Under the synergistic effect of glucose oxidase and ferritin,the equilibrium between reactive oxygen species and GSH is damaged,leading to lipid peroxidation.As a result,by inducing ferroptosis,our self-propelled ferroptosis nanoinducers exhibit enhanced tumor inhibitory effects.This work paves a way for the construction of a biocompatible anticancer platform with enhanced diffusion utilizing only two endogenous proteins,centered around the concept of ferroptosis.展开更多
Self-propelled robots have attracted significant attention due to their remarkable ability to navigate confined terrains.These robots usually have deformable structures while having discontinuous contact forces with t...Self-propelled robots have attracted significant attention due to their remarkable ability to navigate confined terrains.These robots usually have deformable structures while having discontinuous contact forces with the ground,resulting in a complex nonlinear system.To provide a solid foundation for the locomotion prediction and optimization for the self-propelled robots,it is necessary to conduct dynamic modelling and locomotion analysis of the robot.Motivated by these issues,this paper proposes a vibration-driven surrogate dynamic model for a deformable self-propelled robot and presents a detailed dynamic analysis.The surrogate dynamic model is employed to classify various types of stick-slip locomotion.Subsequently,the corresponding experiment demonstrates that the surrogate dynamic model effectively predicts the locomotion of the robot,particularly three types of stick-slip locomotion induced by discontinuous friction.Finally,a multi-objective coordinated optimization regarding the locomotion velocity,the cost of transport,and the energy conversion rate of the self-propelled robot is conducted,aiming to comprehensively enhance the robot’s locomotion performance.Additionally,suggestions for the selection of actuation parameters are presented.展开更多
Comparisons were performed between self-propelled boom sprayer and traditional mechanis, such as knapsack sprayer and sprayer-duster, stretcher-type powered sprayer, as well as single rotor unmanned sprayer and multi-...Comparisons were performed between self-propelled boom sprayer and traditional mechanis, such as knapsack sprayer and sprayer-duster, stretcher-type powered sprayer, as well as single rotor unmanned sprayer and multi-rotor un- manned sprayer. The effects on rice injury, lodging, and rehabilitation were conclud- ed and drug uniform distribution, sedimentation and prevention effects were ana- lyzed. The results showed that the self-propelled boom sprayer is characterized by high degree of automation, convenient operation, high adaptability, and high work efficiency. What＇s more, the sprayed fog quality is better, and fog distribution is more uniform. During the work process, fog loss would be diminished substantially, improving work efficiency and cutting down drug and water. It is notable that the underpart of the sprayer can be widely applied to plant protection in large-scale ar- eas in Jiangsu Province, significantly advancing whole-process mechanization of rice production.展开更多
Numerical simulation and control of self- propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- a...Numerical simulation and control of self- propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- and three-dimensional moving boundary problem, which combines the adaptive multi-grid finite volume method and the methods of immersed boundary and volume of fluid, it is found that due to the interactions of vortices in the wakes, without proper control, a fish school swim with a given flap- ping rule can not keep the fixed shape of a queue. In order to understand the secret of fish swimming, a new feedback con- trol strategy of fish motion is proposed for the first time, i,e., the locomotion speed is adjusted by the flapping frequency of the caudal, and the direction of swimming is controlled by the swinging of the head of a fish. Results show that with this feedback control strategy, a fish school can keep the good order of a queue in cruising, turning or swimming around circles. This new control strategy, which separates the speed control and direction control, is important in the construction of biomimetic robot fish, with which it greatly simplifies the control devices of a biomimetic robot fish.展开更多
Ship resistance issues are related to fuel economy,speed,and cost efficiency.Air lubrication is a promising technique for lowering hull frictional resistance as it is supposed to modify the energy in the turbulent bou...Ship resistance issues are related to fuel economy,speed,and cost efficiency.Air lubrication is a promising technique for lowering hull frictional resistance as it is supposed to modify the energy in the turbulent boundary layer and thereby reduce hull friction.In this paper,the objective is to identify the optimum type of air lubrication using microbubble drag reduction(MBDR)and air layer drag reduction(ALDR)techniques to reduce the resistance of a 56-m Indonesian self-propelled barge(SPB).A model with the following dimensions was constructed:length L=2000 mm,breadth B=521.60 mm,and draft T=52.50 mm.The ship model was towed using standard towing tank experimental parameters.The speed was varied over the Froude number range 0.11–0.31.The air layer flow rate was varied at 80,85,and 90 standard liters per minute(SLPM)and the microbubble injection coefficient over the range 0.20–0.60.The results show that the ship model using the air layer had the highest drag reduction up to a maximum of 90%.Based on the characteristics of the SPB,which operates at low speed,the optimum air lubrication type to reduce resistance in this instance is ALDR.展开更多
We consider the classification of wake structures produced by self-propelled fish-like swimmers based on local measurements of flow variables.This problem is inspired by the extraordinary capability of animal swimmers...We consider the classification of wake structures produced by self-propelled fish-like swimmers based on local measurements of flow variables.This problem is inspired by the extraordinary capability of animal swimmers in perceiving their hydrodynamic environments under dark condition.We train different neural networks to classify wake structures by using the streamwise velocity component,the crosswise velocity component,the vorticity and the combination of three flow variables,respectively.It is found that the neural networks trained using the two velocity components perform well in identifying the wake types,whereas the neural network trained using the vorticity suffers from a high rate of misclassification.When the neural network is trained using the combination of all three flow variables,a remarkably high accuracy in wake classification can be achieved.The results of this study can be helpful to the design of flow sensory systems in robotic underwater vehicles.展开更多
The launch dynamics theory for multibody systems emerges as an innovative and efficacious approach for the study of launch dynamics,capable of addressing the challenges of complex modeling,diminished computational eff...The launch dynamics theory for multibody systems emerges as an innovative and efficacious approach for the study of launch dynamics,capable of addressing the challenges of complex modeling,diminished computational efficiency,and imprecise analyses of system dynamic responses found in the dynamics research of intricate multi-rigid-flexible body systems,such as self-propelled artillery.This advancement aims to enhance the firing accuracy and launch safety of self-propelled artillery.Recognizing the shortfall of overlooking the band engraving process in existing theories,this study introduces a novel coupling calculation methodology for the launch dynamics of a self-propelled artillery multibody system.This method leverages the ABAQUS subroutine interface VUAMP to compute the dynamic response of the projectile and barrel during the launch process of large-caliber self-propelled artillery.Additionally,it examines the changes in projectile resistance and band deformation in relation to projectile motion throughout the band engraving process.Comparative analysis of the computational outcomes with experimental data evidences that the proposed method offers a more precise depiction of the launch process of self-propelled artillery,thereby enhancing the accuracy of launch dynamics calculations for self-propelled artillery.展开更多
Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties.However,to dat...Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties.However,to date self-propelled jumping phenomenon has only been observed and studied on superhydrophobic surfaces,other than those hydrophobic surfaces with weaker but fairish water-repellency,for instance,vulcanized silicon rubber(RTV) coatings.In this work,from the perspective of thermodynamic-based energy balance aspect,the reason that self-propelled jumping phenomenon does not happen on RTV coatings is studied.The apparent contact angles of droplets on RTV coatings can be less than the theoretical critical values therefore cannot promise energy surplus for the coalesced droplets onside.Besides,on RTV and superhydrophobic surfaces,the droplet-size dependent variation characteristics of the energy leftover from the coalescence process are opposite.For the droplets coalescing on RTV coatings,the magnitudes of energy dissipations are more sensitive to the increase in droplet size,compared to that of released surface energy.While for superhydrophobic coatings,the energy generated during the coalescence process can be more sensitive than the dissipations to the change in droplet size.展开更多
The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so on.The Leidenfrost effect can be utilized to significantly re...The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so on.The Leidenfrost effect can be utilized to significantly reduce motion resistance.However,the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical system.To manipulate Leidenfrost droplets,it is necessary to create 2D or quasi-2D geometries.In this study,femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient(SPHG),enabling directional self-propulsion of Leidenfrost droplets.Flow field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the SPHG,resulting in directional propulsion of the inner gas.The viscous force between the gas and liquid then drives the droplet to move.展开更多
The experimental modal analysis of the selected self-propelled gun was completed to obtain its modal frequency distribution and modes by using an operational modal analysis experimental technique.The result obtained b...The experimental modal analysis of the selected self-propelled gun was completed to obtain its modal frequency distribution and modes by using an operational modal analysis experimental technique.The result obtained by the method was compared with that obtained by the traditional method.It indicates that the two results are in good agreement.展开更多
Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration.Resistance at the front end is the main source of resistance to the robot’s motion in t...Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration.Resistance at the front end is the main source of resistance to the robot’s motion in the strata.Since there is no continuous and strong downward drilling force as in conventional drilling rigs,robot movement relies heavily on the drill bit to reduce the drilling resistance.In this study we propose a self-propelling drill bit that can discharge soil debris to provide propulsive force and reduce the resistance.The key parameter of the drill bit design,the spiral blade lead angle,was determined by theoretical analysis of the drill bit’s soil discharging effect.To verify the structural advantages of the self-propelling drill bit in reducing resistance,a comparative analysis with a conventional conical drill bit was conducted.The drilling process of both bits was simulated using finite element simulation at various rotation speeds,the penetration force and torque data of both drill bits were obtained,and tests prepared accordingly in subsea soil were conducted.The simulations and tests verified that the penetration force of the self-propelling drill bit was lower than that of the conventional conical drill bit.The self-propelling drill bit can reduce the resistance effectively,and may play an important role in the stratum movement of drilling robots.展开更多
In this paper, a model that combines the lattice Boltzmann method with the singularity distribution method is proposed to simulate a self-propelled particle swimming（exhibiting translation and rotation） in a channel...In this paper, a model that combines the lattice Boltzmann method with the singularity distribution method is proposed to simulate a self-propelled particle swimming（exhibiting translation and rotation） in a channel flow. The results show that the velocity distribution for a self-propelled particle swimming deviates from a Maxwellian distribution and exhibits highvelocity tails. The influence of an eccentric potential doublet on the translation velocity of the particle is significant. The velocity decay process can be described using a double exponential model form. No large differences in the velocity distribution were observed for different translation Reynolds numbers, rotation Reynolds numbers, or regular intervals.展开更多
Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are...Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests,a new empirical model of shear stressdisplacement relationship for saturated soft-plastic soil(SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher,a test platform,where track segment shear test and drawbar pull test can be performed in seafloor soil substitute(bentonite water mixture),was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces,including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line,drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built,and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.展开更多
Self-propelled nozzle is a critical component of the radial jet drilling technology.Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance.To improve the working pe...Self-propelled nozzle is a critical component of the radial jet drilling technology.Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance.To improve the working performance of the nozzle,the numerical simulation model is built and verified by the experimental results of propulsive force.Then the theoretical model of the energy efficiency and energy coefficient of the nozzle is built to reveal the influence of the structural parameters on the jet performance of the nozzle.The results show that the energy efficiency and energy coefficient of the backward orifice increase first and then decrease with the angle increases.The energy coefficient of forward orifice is almost constant with the angle increases.With the increase in the number and diameter,energy efficiency and energy coefficient of the forward orifice gradually decrease,but the backward orifice energy coefficient first increases and then decreases.Finally,it is obtained that the nozzle has better jet performance when the angle of backward orifice is 30°,the number of backward orifice is 6,and the value range of diameter is 2-2.2 mm.This study provides a reference for the design of efficiently self-propelled nozzle for radial jet drilling technology.展开更多
We studied the rectified transport of underdamped particles subject to phase lag in an asymmetric periodic structure.When the inertia effect is considered,it is possible to observe reversals of the average velocity wi...We studied the rectified transport of underdamped particles subject to phase lag in an asymmetric periodic structure.When the inertia effect is considered,it is possible to observe reversals of the average velocity with small self-propelled force,whereas particles always move in the positive direction with large self-propelled force.The introduction of phase lag leads particles to follow circular orbits and suppress the polar motion.In addition,this can adjust the direction of particle motion.There exists an optimal value of polar interaction strength at which the rectification is maximal.These results open the way for many application processes,such as spatial sorting of particles mixture and separation based on their physical properties.展开更多
The Brownian motion of spherical and ellipsoidal self-propelled particles was simulated without considering the effect of inertia and using the Langevin equation and the diffusion coefficient of ellipsoidal particles ...The Brownian motion of spherical and ellipsoidal self-propelled particles was simulated without considering the effect of inertia and using the Langevin equation and the diffusion coefficient of ellipsoidal particles derived by Perrin.The P´eclet number(Pe)was introduced to measure the relative strengths of self-propelled and Brownian motions.We found that the motion state of spherical and ellipsoid self-propelled particles changed significantly under the influence of Brownian motion.For spherical particles,there were three primary states of motion:1)when Pe<30,the particles were still significantly affected by Brownian motion;2)when Pe>30,the self-propelled velocities of the particles were increasing;and 3)when Pe>100,the particles were completely controlled by the self-propelled velocities and the Brownian motion was suppressed.In the simulation of the ellipsoidal self-propelled particles,we found that the larger the aspect ratio of the particles,the more susceptible they were to the influence of Brownian motion.In addition,the value interval of Pe depended on the aspect ratio.Finally,we found that the directional motion ability of the ellipsoidal self-propelled particles was much weaker than that of the spherical self-propelled particles.展开更多
Conducting hydrodynamic and physical motion simulation tests using a large-scale self-propelled model under actual wave conditions is an important means for researching environmental adaptability of ships. During the ...Conducting hydrodynamic and physical motion simulation tests using a large-scale self-propelled model under actual wave conditions is an important means for researching environmental adaptability of ships. During the navigation test of the self-propelled model, the complex environment including various port facilities, navigation facilities, and the ships nearby must be considered carefully, because in this dense environment the impact of sea waves and winds on the model is particularly significant. In order to improve the security of the self-propelled model, this paper introduces the Q learning based on reinforcement learning combined with chaotic ideas for the model＇s collision avoidance, in order to improve the reliability of the local path planning. Simulation and sea test results show that this algorithm is a better solution for collision avoidance of the self navigation model under the interference of sea winds and waves with good adaptability.展开更多
A minimal cellular automaton model is introduced to describe the collective motion of self-propelled particles on two-dimensional square lattice. The model features discretization of directional and positional spaces ...A minimal cellular automaton model is introduced to describe the collective motion of self-propelled particles on two-dimensional square lattice. The model features discretization of directional and positional spaces and single-particle occupation on one lattice site. Contrary to the Vicsek model and its variants, our model exhibits the nonvanishing optimal noise. When the particle density increases, the collective motion is promoted with optimal noise strength and reduced with noise strength out of optimal region. In addition, when the square lattice undergoes edge percolation process, no abrupt change of alignment behaviors is observed at the critical point of percolation.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12132015,12332015,and 12302333)。
文摘This study investigates the motion behavior of a slender flexible particle in a backward-facing step(BFS)flow using the direct-forcing fictitious domain method,with a particular focus on the trapping phenomena near the separation vortex region.Three distinct motion modes are identified:periodic rotation or oscillation within the vortex(trapping),downstream transport(escape),and transition state exhibiting unstable trapping.A dynamic balance among inward migration,centrifugal effects,wall interactions,and elastic forces enables the particle to achieve stable orbital motion within two distinct limit cycles.The topology of these orbits is governed by parameters,including the aspect ratio,structural flexibility,deformation intensity,and fluid inertia,all of which are characterized by the Reynolds number(Re).Specifically,fluid inertia plays a dominant role in facilitating particle trapping.At a fixed Re,a particle with a smaller aspect ratio tends to migrate inward and become trapped,whereas one with a larger aspect ratio is more likely to escape.Structural flexibility,especially when enhanced by confinement near the wall,leads to elastic deformation that induces secondary vortices and a weak flipping motion.The deformation intensityαsignificantly influences the lateral migration of the slender particle after the initial release;a largerαcauses it to drift toward the channel centerline,increasing the probability of escape.These findings provide a theoretical foundation for optimizing the transport and capture of slender soft swimmers in complex flow environments.
基金supported by National Key Research and Development Program of China(No.2022YFA1206900)National Natural Science Foundation of China(Nos.22175083,82204415,51973241,22375224)GuangDong Basic and Applied Basic Research Foundation(No.2021A1515220187)。
文摘Ferroptosis is a newly proposed type of programmed cell death,which has been associated with a variety of diseases including tumors.Researchers have thereby presented nanoplatforms to mediate ferroptosis for anti-cancer therapy.However,the development of ferroptosis-based nanotherapeutics is generally hindered by the limited penetration depth in tumors,poor active pharmaceutical ingredient(API)loading content and the systemic toxicity.Herein,self-propelled ferroptosis nanoinducers composed of two endogenous proteins,glucose oxidase and ferritin,are presented to show enhanced tumor inhibition via ferroptosis while maintaining high API and biocompatibility.The accumulation of our proteomotors at tumor regions is facilitated by the active tumor-targeting effect of ferritin.The enhanced diffusion of proteomotors is then actuated by efficiently decomposing glucose into gluconic acid and H_(2)O_(2),leading to deeper penetration and enhanced uptake into tumors.Under the synergistic effect of glucose oxidase and ferritin,the equilibrium between reactive oxygen species and GSH is damaged,leading to lipid peroxidation.As a result,by inducing ferroptosis,our self-propelled ferroptosis nanoinducers exhibit enhanced tumor inhibitory effects.This work paves a way for the construction of a biocompatible anticancer platform with enhanced diffusion utilizing only two endogenous proteins,centered around the concept of ferroptosis.
基金supported by the National Natural Science Foundation of China(Grant Nos.11932015,12072237,and 12372022)the Shanghai Gaofeng Project for University Academic Program Development,and the Fundamental Research Funds for the Central Universities(Grant No.22120220590).
文摘Self-propelled robots have attracted significant attention due to their remarkable ability to navigate confined terrains.These robots usually have deformable structures while having discontinuous contact forces with the ground,resulting in a complex nonlinear system.To provide a solid foundation for the locomotion prediction and optimization for the self-propelled robots,it is necessary to conduct dynamic modelling and locomotion analysis of the robot.Motivated by these issues,this paper proposes a vibration-driven surrogate dynamic model for a deformable self-propelled robot and presents a detailed dynamic analysis.The surrogate dynamic model is employed to classify various types of stick-slip locomotion.Subsequently,the corresponding experiment demonstrates that the surrogate dynamic model effectively predicts the locomotion of the robot,particularly three types of stick-slip locomotion induced by discontinuous friction.Finally,a multi-objective coordinated optimization regarding the locomotion velocity,the cost of transport,and the energy conversion rate of the self-propelled robot is conducted,aiming to comprehensively enhance the robot’s locomotion performance.Additionally,suggestions for the selection of actuation parameters are presented.
基金Supported by National Natural Science Foundation of China(31401296)Independent Innovation Foundation of Science and Technology in Jiangsu Province(CX(14)2101)
文摘Comparisons were performed between self-propelled boom sprayer and traditional mechanis, such as knapsack sprayer and sprayer-duster, stretcher-type powered sprayer, as well as single rotor unmanned sprayer and multi-rotor un- manned sprayer. The effects on rice injury, lodging, and rehabilitation were conclud- ed and drug uniform distribution, sedimentation and prevention effects were ana- lyzed. The results showed that the self-propelled boom sprayer is characterized by high degree of automation, convenient operation, high adaptability, and high work efficiency. What＇s more, the sprayed fog quality is better, and fog distribution is more uniform. During the work process, fog loss would be diminished substantially, improving work efficiency and cutting down drug and water. It is notable that the underpart of the sprayer can be widely applied to plant protection in large-scale ar- eas in Jiangsu Province, significantly advancing whole-process mechanization of rice production.
基金supported by the National Natural Science Foundation of China(10172095 and 10672183)
文摘Numerical simulation and control of self- propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- and three-dimensional moving boundary problem, which combines the adaptive multi-grid finite volume method and the methods of immersed boundary and volume of fluid, it is found that due to the interactions of vortices in the wakes, without proper control, a fish school swim with a given flap- ping rule can not keep the fixed shape of a queue. In order to understand the secret of fish swimming, a new feedback con- trol strategy of fish motion is proposed for the first time, i,e., the locomotion speed is adjusted by the flapping frequency of the caudal, and the direction of swimming is controlled by the swinging of the head of a fish. Results show that with this feedback control strategy, a fish school can keep the good order of a queue in cruising, turning or swimming around circles. This new control strategy, which separates the speed control and direction control, is important in the construction of biomimetic robot fish, with which it greatly simplifies the control devices of a biomimetic robot fish.
文摘Ship resistance issues are related to fuel economy,speed,and cost efficiency.Air lubrication is a promising technique for lowering hull frictional resistance as it is supposed to modify the energy in the turbulent boundary layer and thereby reduce hull friction.In this paper,the objective is to identify the optimum type of air lubrication using microbubble drag reduction(MBDR)and air layer drag reduction(ALDR)techniques to reduce the resistance of a 56-m Indonesian self-propelled barge(SPB).A model with the following dimensions was constructed:length L=2000 mm,breadth B=521.60 mm,and draft T=52.50 mm.The ship model was towed using standard towing tank experimental parameters.The speed was varied over the Froude number range 0.11–0.31.The air layer flow rate was varied at 80,85,and 90 standard liters per minute(SLPM)and the microbubble injection coefficient over the range 0.20–0.60.The results show that the ship model using the air layer had the highest drag reduction up to a maximum of 90%.Based on the characteristics of the SPB,which operates at low speed,the optimum air lubrication type to reduce resistance in this instance is ALDR.
基金the National Natural Science Foundation of China(Grants 11772338 and 11372331)Chinese Academy of Sciences(Grants XDB22040104 and XDA22040203).
文摘We consider the classification of wake structures produced by self-propelled fish-like swimmers based on local measurements of flow variables.This problem is inspired by the extraordinary capability of animal swimmers in perceiving their hydrodynamic environments under dark condition.We train different neural networks to classify wake structures by using the streamwise velocity component,the crosswise velocity component,the vorticity and the combination of three flow variables,respectively.It is found that the neural networks trained using the two velocity components perform well in identifying the wake types,whereas the neural network trained using the vorticity suffers from a high rate of misclassification.When the neural network is trained using the combination of all three flow variables,a remarkably high accuracy in wake classification can be achieved.The results of this study can be helpful to the design of flow sensory systems in robotic underwater vehicles.
基金supported by the National Natural Science Foundation of China (Grant Number:12372093)。
文摘The launch dynamics theory for multibody systems emerges as an innovative and efficacious approach for the study of launch dynamics,capable of addressing the challenges of complex modeling,diminished computational efficiency,and imprecise analyses of system dynamic responses found in the dynamics research of intricate multi-rigid-flexible body systems,such as self-propelled artillery.This advancement aims to enhance the firing accuracy and launch safety of self-propelled artillery.Recognizing the shortfall of overlooking the band engraving process in existing theories,this study introduces a novel coupling calculation methodology for the launch dynamics of a self-propelled artillery multibody system.This method leverages the ABAQUS subroutine interface VUAMP to compute the dynamic response of the projectile and barrel during the launch process of large-caliber self-propelled artillery.Additionally,it examines the changes in projectile resistance and band deformation in relation to projectile motion throughout the band engraving process.Comparative analysis of the computational outcomes with experimental data evidences that the proposed method offers a more precise depiction of the launch process of self-propelled artillery,thereby enhancing the accuracy of launch dynamics calculations for self-propelled artillery.
文摘Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties.However,to date self-propelled jumping phenomenon has only been observed and studied on superhydrophobic surfaces,other than those hydrophobic surfaces with weaker but fairish water-repellency,for instance,vulcanized silicon rubber(RTV) coatings.In this work,from the perspective of thermodynamic-based energy balance aspect,the reason that self-propelled jumping phenomenon does not happen on RTV coatings is studied.The apparent contact angles of droplets on RTV coatings can be less than the theoretical critical values therefore cannot promise energy surplus for the coalesced droplets onside.Besides,on RTV and superhydrophobic surfaces,the droplet-size dependent variation characteristics of the energy leftover from the coalescence process are opposite.For the droplets coalescing on RTV coatings,the magnitudes of energy dissipations are more sensitive to the increase in droplet size,compared to that of released surface energy.While for superhydrophobic coatings,the energy generated during the coalescence process can be more sensitive than the dissipations to the change in droplet size.
基金supported by the Beijing Municipal Natural Science Foundation(JQ20015)National Key Research and Development Program of China(No.2022YFB4601300)+3 种基金the National Science Fund for Distinguished Young Scholars(No.52325505)the National Natural Science Foundation of China(NSFC)(No.52075041)the Joint Funds of the National Natural Science Foundation of China(Grant No.U2037205)the Open Project Program of Wuhan National Laboratory for Optoelectronics(No2021WNLOKF016)。
文摘The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so on.The Leidenfrost effect can be utilized to significantly reduce motion resistance.However,the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical system.To manipulate Leidenfrost droplets,it is necessary to create 2D or quasi-2D geometries.In this study,femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient(SPHG),enabling directional self-propulsion of Leidenfrost droplets.Flow field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the SPHG,resulting in directional propulsion of the inner gas.The viscous force between the gas and liquid then drives the droplet to move.
文摘The experimental modal analysis of the selected self-propelled gun was completed to obtain its modal frequency distribution and modes by using an operational modal analysis experimental technique.The result obtained by the method was compared with that obtained by the traditional method.It indicates that the two results are in good agreement.
基金supported by the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(No.2021JJLH0051)the Finance Science and Technology Project of Hainan Province(No.ZDKJ202019)the 2020 Research Program of Sanya Yazhou Bay Science and Technology City(No.SKYC-2020-01-001),China.
文摘Robotic subsea stratum drilling robot is a method for new subsea stratigraphic geological investigation and resource exploration.Resistance at the front end is the main source of resistance to the robot’s motion in the strata.Since there is no continuous and strong downward drilling force as in conventional drilling rigs,robot movement relies heavily on the drill bit to reduce the drilling resistance.In this study we propose a self-propelling drill bit that can discharge soil debris to provide propulsive force and reduce the resistance.The key parameter of the drill bit design,the spiral blade lead angle,was determined by theoretical analysis of the drill bit’s soil discharging effect.To verify the structural advantages of the self-propelling drill bit in reducing resistance,a comparative analysis with a conventional conical drill bit was conducted.The drilling process of both bits was simulated using finite element simulation at various rotation speeds,the penetration force and torque data of both drill bits were obtained,and tests prepared accordingly in subsea soil were conducted.The simulations and tests verified that the penetration force of the self-propelling drill bit was lower than that of the conventional conical drill bit.The self-propelling drill bit can reduce the resistance effectively,and may play an important role in the stratum movement of drilling robots.
基金supported by the National Natural Science Foundation of China(Grant No.11632016)
文摘In this paper, a model that combines the lattice Boltzmann method with the singularity distribution method is proposed to simulate a self-propelled particle swimming（exhibiting translation and rotation） in a channel flow. The results show that the velocity distribution for a self-propelled particle swimming deviates from a Maxwellian distribution and exhibits highvelocity tails. The influence of an eccentric potential doublet on the translation velocity of the particle is significant. The velocity decay process can be described using a double exponential model form. No large differences in the velocity distribution were observed for different translation Reynolds numbers, rotation Reynolds numbers, or regular intervals.
文摘Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests,a new empirical model of shear stressdisplacement relationship for saturated soft-plastic soil(SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher,a test platform,where track segment shear test and drawbar pull test can be performed in seafloor soil substitute(bentonite water mixture),was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces,including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line,drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built,and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.
基金the paper was supported by the Natural Science Foundation of China(No.51974036 and No.51604039)the Yangtze Fund for Youth Teams of Science and Technology Innovation(No.2016cqt01)。
文摘Self-propelled nozzle is a critical component of the radial jet drilling technology.Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance.To improve the working performance of the nozzle,the numerical simulation model is built and verified by the experimental results of propulsive force.Then the theoretical model of the energy efficiency and energy coefficient of the nozzle is built to reveal the influence of the structural parameters on the jet performance of the nozzle.The results show that the energy efficiency and energy coefficient of the backward orifice increase first and then decrease with the angle increases.The energy coefficient of forward orifice is almost constant with the angle increases.With the increase in the number and diameter,energy efficiency and energy coefficient of the forward orifice gradually decrease,but the backward orifice energy coefficient first increases and then decreases.Finally,it is obtained that the nozzle has better jet performance when the angle of backward orifice is 30°,the number of backward orifice is 6,and the value range of diameter is 2-2.2 mm.This study provides a reference for the design of efficiently self-propelled nozzle for radial jet drilling technology.
基金Project supported by the National Natural Science Foundation of China(Grant No.12075090)the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2019B030330001)+2 种基金the Science and Technology Program of Guangzhou City(Grant No.2019050001)the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030313029)the Major Basic Research Project of Guangdong Province,China(Grant No.2017KZDXM024)。
文摘We studied the rectified transport of underdamped particles subject to phase lag in an asymmetric periodic structure.When the inertia effect is considered,it is possible to observe reversals of the average velocity with small self-propelled force,whereas particles always move in the positive direction with large self-propelled force.The introduction of phase lag leads particles to follow circular orbits and suppress the polar motion.In addition,this can adjust the direction of particle motion.There exists an optimal value of polar interaction strength at which the rectification is maximal.These results open the way for many application processes,such as spatial sorting of particles mixture and separation based on their physical properties.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12372251 and 12132015)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.2023YW69).
文摘The Brownian motion of spherical and ellipsoidal self-propelled particles was simulated without considering the effect of inertia and using the Langevin equation and the diffusion coefficient of ellipsoidal particles derived by Perrin.The P´eclet number(Pe)was introduced to measure the relative strengths of self-propelled and Brownian motions.We found that the motion state of spherical and ellipsoid self-propelled particles changed significantly under the influence of Brownian motion.For spherical particles,there were three primary states of motion:1)when Pe<30,the particles were still significantly affected by Brownian motion;2)when Pe>30,the self-propelled velocities of the particles were increasing;and 3)when Pe>100,the particles were completely controlled by the self-propelled velocities and the Brownian motion was suppressed.In the simulation of the ellipsoidal self-propelled particles,we found that the larger the aspect ratio of the particles,the more susceptible they were to the influence of Brownian motion.In addition,the value interval of Pe depended on the aspect ratio.Finally,we found that the directional motion ability of the ellipsoidal self-propelled particles was much weaker than that of the spherical self-propelled particles.
基金Foundation item： Supported by the National Natural Science Foundation of China under Grant No.61100005.
文摘Conducting hydrodynamic and physical motion simulation tests using a large-scale self-propelled model under actual wave conditions is an important means for researching environmental adaptability of ships. During the navigation test of the self-propelled model, the complex environment including various port facilities, navigation facilities, and the ships nearby must be considered carefully, because in this dense environment the impact of sea waves and winds on the model is particularly significant. In order to improve the security of the self-propelled model, this paper introduces the Q learning based on reinforcement learning combined with chaotic ideas for the model＇s collision avoidance, in order to improve the reliability of the local path planning. Simulation and sea test results show that this algorithm is a better solution for collision avoidance of the self navigation model under the interference of sea winds and waves with good adaptability.
基金Project supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)the National Natural Science Foundation of China(Grant No.12090054)。
文摘A minimal cellular automaton model is introduced to describe the collective motion of self-propelled particles on two-dimensional square lattice. The model features discretization of directional and positional spaces and single-particle occupation on one lattice site. Contrary to the Vicsek model and its variants, our model exhibits the nonvanishing optimal noise. When the particle density increases, the collective motion is promoted with optimal noise strength and reduced with noise strength out of optimal region. In addition, when the square lattice undergoes edge percolation process, no abrupt change of alignment behaviors is observed at the critical point of percolation.
