Soft robotic crawlers have limited payload capacity and crawling speed.This study proposes a high-performance inchworm-like modular robotic crawler based on fluidic prestressed composite(FPC)actuators.The FPC actuator...Soft robotic crawlers have limited payload capacity and crawling speed.This study proposes a high-performance inchworm-like modular robotic crawler based on fluidic prestressed composite(FPC)actuators.The FPC actuator is precurved and a pneumatic source is used to flatten it,requiring no energy cost to maintain the equilibrium curved shape.Pressurizing and depressurizing the actuators generate alternating stretching and bending motions of the actuators,achieving the crawling motion of the robotic crawler.Multi-modal locomotion(crawling,turning,and pipe climbing)is achieved by modular reconfiguration and gait design.An analytical kinematic model is proposed to characterize the quasi-static curvature and step size of a single-module crawler.Multiple configurations of robotic crawlers are fabricated to demonstrate the crawling ability of the proposed design.A set of systematic experiments are set up and conducted to understand how crawler responses vary as a function of FPC prestrains,input pressures,and actuation frequencies.As per the experiments,the maximum carrying load ratio(carrying load divided by robot weight)is found to be 22.32,and the highest crawling velocity is 3.02 body length(BL)per second(392 mm/s).Multi-modal capabilities are demonstrated by reconfiguring three soft crawlers,including a matrix crawler robot crawling in amphibious environments,and an inching crawler turning at an angular velocity of 2/s,as well as earthworm-like crawling robots climbing a 20 inclination slope and pipe.展开更多
The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inhere...The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inherent limitation,that is,the spreading angle cannot be controlled independently,rather by the jet volume flow rate and internal geometry.Accordingly,two types of fluidic oscillators based on the master-slave design are developed in current study to decouple this correlation.In both designs,the master layer inherits the similar oscillation mechanisms of a sweeping jet,and the slave layer resembles a steady jet channel.The difference between the two designs is that Design A has a short diverging exit in the slave layer,but Design B adds a long interaction chamber in the exit channel to intensify flow instability.The external flow fields and governing oscillation properties of these two designs are experimentally explored with time-resolved Particle Image Velocimetry(PIV),while the internal flow dynamics and driving oscillation mechanisms are numerically investigated.By fixing the total volume flow rate,the jet spreading angle of Design A can be increased smoothly from 0°to above 100°by increasing the proportion of master layer’s flow rate from 0 to 100%.For Design B,the control authority of the master layer is significantly enhanced by adding the interaction chamber in the slave layer.In addition,the added chamber causes notable jet oscillation even when the master layer has none input.展开更多
Over the past two decades,digital microfluidic biochips have been in much demand for safety-critical and biomedical applications and increasingly important in point-of-care analysis,drug discovery,and immunoassays,amo...Over the past two decades,digital microfluidic biochips have been in much demand for safety-critical and biomedical applications and increasingly important in point-of-care analysis,drug discovery,and immunoassays,among other areas.However,for complex bioassays,finding routes for the transportation of droplets in an electrowetting-on-dielectric digital biochip while maintaining their discreteness is a challenging task.In this study,we propose a deep reinforcement learning-based droplet routing technique for digital microfluidic biochips.The technique is implemented on a distributed architecture to optimize the possible paths for predefined source–target pairs of droplets.The actors of the technique calculate the possible routes of the source–target pairs and store the experience in a replay buffer,and the learner fetches the experiences and updates the routing paths.The proposed algorithm was applied to benchmark suitesⅠand Ⅲ as two different test benches,and it achieved significant improvements over state-of-the-art techniques.展开更多
The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are...The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.展开更多
As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. Howeve...As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.展开更多
A type of supersonic fluidic oscillator is proposed and its ability to generate pulsating supersonic jet is proved in this paper.Unsteady two-dimensional numerical simulations reveal that the fluid transforms from sub...A type of supersonic fluidic oscillator is proposed and its ability to generate pulsating supersonic jet is proved in this paper.Unsteady two-dimensional numerical simulations reveal that the fluid transforms from subsonic to supersonic condition in the mixing chamber of oscillator after the supplied flow pressure increases from 1.1×105 Pa to 5.0×105 Pa.When the supersonic flow is formed inside the oscillator,the wall-attached flow represents expansion wave and compression wave alternately.The oscillating frequency will saturate to a certain value with the increase of supplied pressure.Examination of the internal fluid dynamics indicates that the flow direction inside the FeedBack Channel(FBC)is related to the change of the local pressure at the inlet and the outlet of the feedback channel.The vortices produced in the mixing chamber present different distribution characteristics with the change of the fluid’s direction in the FBC.The sweeping jet is divided into two jets with varying flow rate over time by the splitter.In the end of two channels,two jets are accelerated above sound speed by convergent-divergent nozzle.Therefore,pulsating supersonic jets are produced at two outlets for this type of fluidic oscillator.展开更多
Compliant mobile robotics is a developing bioinspired concept of propulsion for locomotion.This paper studies the modeling and analysis of a compliant tail-propelled fish-like robot.This biomimetic design uses a fluid...Compliant mobile robotics is a developing bioinspired concept of propulsion for locomotion.This paper studies the modeling and analysis of a compliant tail-propelled fish-like robot.This biomimetic design uses a fluid-filled network of channels embedded into the soft body to actuate the compliant tail and generate thrust.This study analyzes the nonlinear dynamics of Fish Tail Fluidic Actuator(FTFA).The fluidic expansion under pressure creates a bending moment in the tail.It is demonstrated that the tail response follows the theoretical formulation extracted from the accurate modeling.In this modeling,tail is assumed as a continuous Euler–Bernoulli beam considering large deflection and nonlinear strain.Then,the implementation of Hamilton's principle and the method of calculation lead to the motion equations.The assumed mode method is used to achieve the mathematical model in the multi-mode system that is more similar to the soft continuous system.We investigate the tendencies of the tail amplitude,swimming speed,and Strouhal number when the input driving frequency changes.The simulation results disclose that high swimming efficiency can be obtained at the multi-order resonances;meanwhile,the compliant fish robot is pushed at the corresponding frequency illustrating nonlinear behavior.展开更多
A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse...A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard <em>k-ε</em> model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of 5<span style="white-space:nowrap;">°</span> taper angle.展开更多
Fluidic oscillators(FOs)can be used as an efficient fluidic vibration tool to solve high friction problems in extended-reach wells.However,the complex mechanism of FOs makes the design challenging,and the dynamic eros...Fluidic oscillators(FOs)can be used as an efficient fluidic vibration tool to solve high friction problems in extended-reach wells.However,the complex mechanism of FOs makes the design challenging,and the dynamic erosion behavior inside FOs is still unclear.In this paper,new FOs are proposed and the working characteristics under the influence of periodic particle-laden jets are investigated.Firstly,the results reveal the working mechanism of new FOs,showing that the generation of pressure pulses is closely connected with periodic jet switching and the development of vortices.Secondly,the important performance parameters,i.e.,pressure pulse and oscillation frequency,are extensively studied through numerical simulation and experimental verification.It is found that the performance can be optimized by adjusting the tool structure according to different engineering requirements.Finally,the oscillating solid-liquid two-phase flow inside FO is studied.It is demonstrated that the accumulation of particles leads to a significant reduction in performance.The results also reveal five locations that are susceptible to erosion and the erosion behavior of these locations are studied.It has been shown that the periodic jet causes fluctuations in the amount of erosion at the outlet and splitter.This research can provide valuable references for the design and optimization of vibration friction-reduction tools.展开更多
Enhanced gas-liquid mass transfer is significant for the desulfurization and denitration of ship exhaust gases.As a fluid device,the special structure of the fluidic oscillator generates self-excited oscillations that...Enhanced gas-liquid mass transfer is significant for the desulfurization and denitration of ship exhaust gases.As a fluid device,the special structure of the fluidic oscillator generates self-excited oscillations that can effectively enhance the mass transfer process of gas-liquid.But there are few studies on the internal gas-liquid flow.The transportation of individual bubbles in the fluidic oscillator was investigated by a high-speed camera and digital image analysis.The results show that the bubble experienced a significant deceleration process in the chamber region of the fluidic oscillator.In addition,the maximum bubble offset increased with the diameter of the initial bubble.The trajectory of the bubble showed zigzag movement due to the deflecting oscillation of the fluidic oscillator.At the same time,the deformation of the bubble was intensified by the deflecting oscillation.The deformation ratio of the bubble increased with the increase of Reynolds number.By studying the transport process of a single bubble in the fluid oscillator,it is considered that the fluid oscillator has the potential to be a new bubble generator.展开更多
This paper elaborates a nonlinear fluidic low frequency vibration isolator designed with the characteristics of quasi-zero stiffness(QZS).The existing model of QZS vibration isolator enhances amplitude of vibration an...This paper elaborates a nonlinear fluidic low frequency vibration isolator designed with the characteristics of quasi-zero stiffness(QZS).The existing model of QZS vibration isolator enhances amplitude of vibration and attenuating vibration frequencies.This concern with displacement plays a vital role in the performance and instability of oblique spring setup reduces the isolator performance in horizontal non-nominal loads,in this accordance;this paper associates double acting hydraulic cylinder(fluidic actuators in short)in oblique and helical coil spring.An approximate expression of unique analytical relationship between the stiffness of vertical spring and bulk modulus of the fluid is derived for Quasi–Zero Stiffness Non-Linear Vibration Isolator with Fluidic Actuators(NLVIFA in short)system and the force transmissibility is formulated and damping ratio are discussed for characteristic analysis.Modal analysis carried out and compared with analytical results and an experimental prototype is developed and investigated.The performance of the NLVIFA reduces the external embarrassment more at low frequencies and the series of experimental studies showing that the soft nonlinearity causes limitation in the resonant frequency thereupon the isolation will be enhanced and NLVIFA greatly outperform some other type of nonlinear isolators.展开更多
A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successf...A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.展开更多
PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing ...PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction.In this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with ANSYS.With the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of nozzle.The L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/R.The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle.The simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.展开更多
Ionic fluidic devices are gaining interest due to their role in enabling self-powered neuromorphic computing systems.In this study,we present an approach that integrates an iontronic fluidic memristive(IFM)device with...Ionic fluidic devices are gaining interest due to their role in enabling self-powered neuromorphic computing systems.In this study,we present an approach that integrates an iontronic fluidic memristive(IFM)device with low input impedance and a triboelectric nanogenerator(TENG)based on ferrofluid(FF),which has high input impedance.By incorporating contact separation electromagnetic(EMG)signals with low input impedance into our FF TENG device,we enhance the FF TENG’s performance by increasing energy harvesting,thereby enabling the autonomous powering of IFM devices for self-powered computing.Further,replicating neuronal activities using artificial iontronic fluidic systems is key to advancing neuromorphic computing.These fluidic devices,composed of soft-matter materials,dynamically adjust their conductance by altering the solution interface.We developed voltage-controlled memristor and memcapacitor memory in polydimethylsiloxane(PDMS)structures,utilising a fluidic interface of FF and polyacrylic acid partial sodium salt(PAA Na^(+)).The confined ion interactions in this system induce hysteresis in ion transport across various frequencies,resulting in significant ion memory effects.Our IFM successfully replicates diverse electric pulse patterns,making it highly suitable for neuromorphic computing.Furthermore,our system demonstrates synapse-like learning functions,storing and retrieving short-term(STM)and long-term memory(LTM).The fluidic memristor exhibits dynamic synapse-like features,making it a promising candidate for the hardware implementation of neural networks.FF TENG/EMG device adaptability and seamless integration with biological systems enable the development of advanced neuromorphic devices using iontronic fluidic materials,further enhanced by intricate chemical designs for self-powered electronics.展开更多
A pair of unidirectional turbines(UT)can operate in oscillatory airflow without additional units.However,this arrangement suffers from poor flow rectification.A fluidic diode(FD)offers variable hydrodynamic resistance...A pair of unidirectional turbines(UT)can operate in oscillatory airflow without additional units.However,this arrangement suffers from poor flow rectification.A fluidic diode(FD)offers variable hydrodynamic resistance based on the flow direction,and this can be coupled with UT to improve flow rectification.In this work,a numerical investigation on the effect of FD with UT is presented using the commercial fluid dynamics software ANSYS Fluent 16.1 with k-ωSST turbulence closure model.Periodic domains of UT and FD are numerically validated individually with experimental results.Later,both are coupled to obtain the combined effect,and these results are compared with the analytical approach.It was observed that coupling FD with UT improved the unit's performance at the lower flow coefficient(<1),but its performance decreased as the flow coefficient increased.Due to the diode's presence,fluid leaving the turbine experiences higher resistance at a higher flow coefficient,which decreases the overall performance of the combined unit.展开更多
In this study, we present speed and displacement measurements of micro-fluid in a hollow-core optical fiber, where an optical interference signal is created by two guided beams reflected at a fixed facet and a moving ...In this study, we present speed and displacement measurements of micro-fluid in a hollow-core optical fiber, where an optical interference signal is created by two guided beams reflected at a fixed facet and a moving fluid end. By counting the number of intensity oscillations of the signal, the movement of the fluid end is successfully traced with high accuracy. Furthermore, we could detect the change in curvature diameters of the fluid end depending on the flow direction by monitoring the visibility of the interference signal.展开更多
Three-dimensional(3D)particle focusing in microfluidics is a fundamental capability with a wide range of applications,such as on-chip flow cytometry,where high-throughput analysis at the single-cell level is performed...Three-dimensional(3D)particle focusing in microfluidics is a fundamental capability with a wide range of applications,such as on-chip flow cytometry,where high-throughput analysis at the single-cell level is performed.Currently,3D focusing is achieved mainly in devices with complex layouts,additional sheath fluids,and complex pumping systems.In this work,we present a compact microfluidic device capable of 3D particle focusing at high flow rates and with a small footprint,without the requirement of external fields or lateral sheath flows,but using only a single-inlet,single-outlet microfluidic sequence of straight channels and tightly curving vertical loops.This device exploits inertial fluidic effects that occur in a laminar regime at sufficiently high flow rates,manipulating the particle positions by the combination of inertial lift forces and Dean drag forces.The device is fabricated by femtosecond laser irradiation followed by chemical etching,which is a simple two-step process enabling the creation of 3D microfluidic networks in fused silica glass substrates.The use of tightly curving three-dimensional microfluidic loops produces strong Dean drag forces along the whole loop but also induces an asymmetric Dean flow decay in the subsequent straight channel,thus producing rapid cross-sectional mixing flows that assist with 3D particle focusing.The use of out-of-plane loops favors a compact parallelization of multiple focusing channels,allowing one to process large amounts of samples.In addition,the low fluidic resistance of the channel network is compatible with vacuum driven flows.The resulting device is quite interesting for high-throughput on-chip flow cytometry.展开更多
To address the temperature cross-talk issue in detecting heavy metal ions in natural waters, a highly-integrated and fully fiber-optic metal ion sensing system capable of temperature-concentration decoupling measureme...To address the temperature cross-talk issue in detecting heavy metal ions in natural waters, a highly-integrated and fully fiber-optic metal ion sensing system capable of temperature-concentration decoupling measurement has been designed. This system integrates a fluidic detection structure assisted by side-polished fibers(SPFs) with a Sagnac interferometer.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.62203174the Guangzhou Municipal Science and Technology Project under Grant No.202201010179.
文摘Soft robotic crawlers have limited payload capacity and crawling speed.This study proposes a high-performance inchworm-like modular robotic crawler based on fluidic prestressed composite(FPC)actuators.The FPC actuator is precurved and a pneumatic source is used to flatten it,requiring no energy cost to maintain the equilibrium curved shape.Pressurizing and depressurizing the actuators generate alternating stretching and bending motions of the actuators,achieving the crawling motion of the robotic crawler.Multi-modal locomotion(crawling,turning,and pipe climbing)is achieved by modular reconfiguration and gait design.An analytical kinematic model is proposed to characterize the quasi-static curvature and step size of a single-module crawler.Multiple configurations of robotic crawlers are fabricated to demonstrate the crawling ability of the proposed design.A set of systematic experiments are set up and conducted to understand how crawler responses vary as a function of FPC prestrains,input pressures,and actuation frequencies.As per the experiments,the maximum carrying load ratio(carrying load divided by robot weight)is found to be 22.32,and the highest crawling velocity is 3.02 body length(BL)per second(392 mm/s).Multi-modal capabilities are demonstrated by reconfiguring three soft crawlers,including a matrix crawler robot crawling in amphibious environments,and an inching crawler turning at an angular velocity of 2/s,as well as earthworm-like crawling robots climbing a 20 inclination slope and pipe.
基金financial support from the National Natural Science Foundation of China(Nos.12072196 and 11702172)Science and Technology Commission of Shanghai Municipality(No.19JC1412900)+1 种基金Aeronautics Power Foundation(No.6141B09050393)Key Laboratory of Aerodynamic Noise Control(No.ANCL20190106)extended to this study。
文摘The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inherent limitation,that is,the spreading angle cannot be controlled independently,rather by the jet volume flow rate and internal geometry.Accordingly,two types of fluidic oscillators based on the master-slave design are developed in current study to decouple this correlation.In both designs,the master layer inherits the similar oscillation mechanisms of a sweeping jet,and the slave layer resembles a steady jet channel.The difference between the two designs is that Design A has a short diverging exit in the slave layer,but Design B adds a long interaction chamber in the exit channel to intensify flow instability.The external flow fields and governing oscillation properties of these two designs are experimentally explored with time-resolved Particle Image Velocimetry(PIV),while the internal flow dynamics and driving oscillation mechanisms are numerically investigated.By fixing the total volume flow rate,the jet spreading angle of Design A can be increased smoothly from 0°to above 100°by increasing the proportion of master layer’s flow rate from 0 to 100%.For Design B,the control authority of the master layer is significantly enhanced by adding the interaction chamber in the slave layer.In addition,the added chamber causes notable jet oscillation even when the master layer has none input.
文摘Over the past two decades,digital microfluidic biochips have been in much demand for safety-critical and biomedical applications and increasingly important in point-of-care analysis,drug discovery,and immunoassays,among other areas.However,for complex bioassays,finding routes for the transportation of droplets in an electrowetting-on-dielectric digital biochip while maintaining their discreteness is a challenging task.In this study,we propose a deep reinforcement learning-based droplet routing technique for digital microfluidic biochips.The technique is implemented on a distributed architecture to optimize the possible paths for predefined source–target pairs of droplets.The actors of the technique calculate the possible routes of the source–target pairs and store the experience in a replay buffer,and the learner fetches the experiences and updates the routing paths.The proposed algorithm was applied to benchmark suitesⅠand Ⅲ as two different test benches,and it achieved significant improvements over state-of-the-art techniques.
基金Project supported by the National Basic Research Program (973) of China (No.2006CB705400)the National Natural Science Foundation of China (No.50575200)
文摘The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.
文摘As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.
基金supported by the National Science and Technology Major Project(No.2017-III-0011-0037)。
文摘A type of supersonic fluidic oscillator is proposed and its ability to generate pulsating supersonic jet is proved in this paper.Unsteady two-dimensional numerical simulations reveal that the fluid transforms from subsonic to supersonic condition in the mixing chamber of oscillator after the supplied flow pressure increases from 1.1×105 Pa to 5.0×105 Pa.When the supersonic flow is formed inside the oscillator,the wall-attached flow represents expansion wave and compression wave alternately.The oscillating frequency will saturate to a certain value with the increase of supplied pressure.Examination of the internal fluid dynamics indicates that the flow direction inside the FeedBack Channel(FBC)is related to the change of the local pressure at the inlet and the outlet of the feedback channel.The vortices produced in the mixing chamber present different distribution characteristics with the change of the fluid’s direction in the FBC.The sweeping jet is divided into two jets with varying flow rate over time by the splitter.In the end of two channels,two jets are accelerated above sound speed by convergent-divergent nozzle.Therefore,pulsating supersonic jets are produced at two outlets for this type of fluidic oscillator.
文摘Compliant mobile robotics is a developing bioinspired concept of propulsion for locomotion.This paper studies the modeling and analysis of a compliant tail-propelled fish-like robot.This biomimetic design uses a fluid-filled network of channels embedded into the soft body to actuate the compliant tail and generate thrust.This study analyzes the nonlinear dynamics of Fish Tail Fluidic Actuator(FTFA).The fluidic expansion under pressure creates a bending moment in the tail.It is demonstrated that the tail response follows the theoretical formulation extracted from the accurate modeling.In this modeling,tail is assumed as a continuous Euler–Bernoulli beam considering large deflection and nonlinear strain.Then,the implementation of Hamilton's principle and the method of calculation lead to the motion equations.The assumed mode method is used to achieve the mathematical model in the multi-mode system that is more similar to the soft continuous system.We investigate the tendencies of the tail amplitude,swimming speed,and Strouhal number when the input driving frequency changes.The simulation results disclose that high swimming efficiency can be obtained at the multi-order resonances;meanwhile,the compliant fish robot is pushed at the corresponding frequency illustrating nonlinear behavior.
文摘A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard <em>k-ε</em> model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of 5<span style="white-space:nowrap;">°</span> taper angle.
基金funded by the National Key Research and Development Program of China under grant number 2020YFC1807200the National Natural Science Foundation of China under grant number 41872186the National Natural Science Foundation of China(Grant number 51978674)。
文摘Fluidic oscillators(FOs)can be used as an efficient fluidic vibration tool to solve high friction problems in extended-reach wells.However,the complex mechanism of FOs makes the design challenging,and the dynamic erosion behavior inside FOs is still unclear.In this paper,new FOs are proposed and the working characteristics under the influence of periodic particle-laden jets are investigated.Firstly,the results reveal the working mechanism of new FOs,showing that the generation of pressure pulses is closely connected with periodic jet switching and the development of vortices.Secondly,the important performance parameters,i.e.,pressure pulse and oscillation frequency,are extensively studied through numerical simulation and experimental verification.It is found that the performance can be optimized by adjusting the tool structure according to different engineering requirements.Finally,the oscillating solid-liquid two-phase flow inside FO is studied.It is demonstrated that the accumulation of particles leads to a significant reduction in performance.The results also reveal five locations that are susceptible to erosion and the erosion behavior of these locations are studied.It has been shown that the periodic jet causes fluctuations in the amount of erosion at the outlet and splitter.This research can provide valuable references for the design and optimization of vibration friction-reduction tools.
基金This work was supported by the National Natural Science Foundation of China(No.22178329)the Taishan Scholars Program,the Shandong Provincial Natural Science Foundation(Nos.ZR2020ME175,ZR2020QE192)the Fundamental Research Funds for the Central Universities(No.202165002).
文摘Enhanced gas-liquid mass transfer is significant for the desulfurization and denitration of ship exhaust gases.As a fluid device,the special structure of the fluidic oscillator generates self-excited oscillations that can effectively enhance the mass transfer process of gas-liquid.But there are few studies on the internal gas-liquid flow.The transportation of individual bubbles in the fluidic oscillator was investigated by a high-speed camera and digital image analysis.The results show that the bubble experienced a significant deceleration process in the chamber region of the fluidic oscillator.In addition,the maximum bubble offset increased with the diameter of the initial bubble.The trajectory of the bubble showed zigzag movement due to the deflecting oscillation of the fluidic oscillator.At the same time,the deformation of the bubble was intensified by the deflecting oscillation.The deformation ratio of the bubble increased with the increase of Reynolds number.By studying the transport process of a single bubble in the fluid oscillator,it is considered that the fluid oscillator has the potential to be a new bubble generator.
文摘This paper elaborates a nonlinear fluidic low frequency vibration isolator designed with the characteristics of quasi-zero stiffness(QZS).The existing model of QZS vibration isolator enhances amplitude of vibration and attenuating vibration frequencies.This concern with displacement plays a vital role in the performance and instability of oblique spring setup reduces the isolator performance in horizontal non-nominal loads,in this accordance;this paper associates double acting hydraulic cylinder(fluidic actuators in short)in oblique and helical coil spring.An approximate expression of unique analytical relationship between the stiffness of vertical spring and bulk modulus of the fluid is derived for Quasi–Zero Stiffness Non-Linear Vibration Isolator with Fluidic Actuators(NLVIFA in short)system and the force transmissibility is formulated and damping ratio are discussed for characteristic analysis.Modal analysis carried out and compared with analytical results and an experimental prototype is developed and investigated.The performance of the NLVIFA reduces the external embarrassment more at low frequencies and the series of experimental studies showing that the soft nonlinearity causes limitation in the resonant frequency thereupon the isolation will be enhanced and NLVIFA greatly outperform some other type of nonlinear isolators.
基金This work was financially supported by the National Natural Science Foundation of China. （No.20271033, 20335020, 90408014）.
文摘A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.
基金Supported by′111′Project and Chongqing Natural Science Foundation(2006BB2043,2006BB2142)
文摘PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction.In this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with ANSYS.With the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of nozzle.The L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/R.The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle.The simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.
基金supported by the System on Chip Lab grant from the Khalifa University of Science and Technology under awards Nos.8474000134 and 8474000137.
文摘Ionic fluidic devices are gaining interest due to their role in enabling self-powered neuromorphic computing systems.In this study,we present an approach that integrates an iontronic fluidic memristive(IFM)device with low input impedance and a triboelectric nanogenerator(TENG)based on ferrofluid(FF),which has high input impedance.By incorporating contact separation electromagnetic(EMG)signals with low input impedance into our FF TENG device,we enhance the FF TENG’s performance by increasing energy harvesting,thereby enabling the autonomous powering of IFM devices for self-powered computing.Further,replicating neuronal activities using artificial iontronic fluidic systems is key to advancing neuromorphic computing.These fluidic devices,composed of soft-matter materials,dynamically adjust their conductance by altering the solution interface.We developed voltage-controlled memristor and memcapacitor memory in polydimethylsiloxane(PDMS)structures,utilising a fluidic interface of FF and polyacrylic acid partial sodium salt(PAA Na^(+)).The confined ion interactions in this system induce hysteresis in ion transport across various frequencies,resulting in significant ion memory effects.Our IFM successfully replicates diverse electric pulse patterns,making it highly suitable for neuromorphic computing.Furthermore,our system demonstrates synapse-like learning functions,storing and retrieving short-term(STM)and long-term memory(LTM).The fluidic memristor exhibits dynamic synapse-like features,making it a promising candidate for the hardware implementation of neural networks.FF TENG/EMG device adaptability and seamless integration with biological systems enable the development of advanced neuromorphic devices using iontronic fluidic materials,further enhanced by intricate chemical designs for self-powered electronics.
基金performed as a Grant-in-Aid for Early-Career Scientists(No.22K14434)supported by the Japan Society for the Promotion of Science(JSPS)JSPS for their financial help in conducting this studyⅡT Madras for the computational facility and financial help to present part of the work in AJWTF-2020。
文摘A pair of unidirectional turbines(UT)can operate in oscillatory airflow without additional units.However,this arrangement suffers from poor flow rectification.A fluidic diode(FD)offers variable hydrodynamic resistance based on the flow direction,and this can be coupled with UT to improve flow rectification.In this work,a numerical investigation on the effect of FD with UT is presented using the commercial fluid dynamics software ANSYS Fluent 16.1 with k-ωSST turbulence closure model.Periodic domains of UT and FD are numerically validated individually with experimental results.Later,both are coupled to obtain the combined effect,and these results are compared with the analytical approach.It was observed that coupling FD with UT improved the unit's performance at the lower flow coefficient(<1),but its performance decreased as the flow coefficient increased.Due to the diode's presence,fluid leaving the turbine experiences higher resistance at a higher flow coefficient,which decreases the overall performance of the combined unit.
文摘In this study, we present speed and displacement measurements of micro-fluid in a hollow-core optical fiber, where an optical interference signal is created by two guided beams reflected at a fixed facet and a moving fluid end. By counting the number of intensity oscillations of the signal, the movement of the fluid end is successfully traced with high accuracy. Furthermore, we could detect the change in curvature diameters of the fluid end depending on the flow direction by monitoring the visibility of the interference signal.
文摘Three-dimensional(3D)particle focusing in microfluidics is a fundamental capability with a wide range of applications,such as on-chip flow cytometry,where high-throughput analysis at the single-cell level is performed.Currently,3D focusing is achieved mainly in devices with complex layouts,additional sheath fluids,and complex pumping systems.In this work,we present a compact microfluidic device capable of 3D particle focusing at high flow rates and with a small footprint,without the requirement of external fields or lateral sheath flows,but using only a single-inlet,single-outlet microfluidic sequence of straight channels and tightly curving vertical loops.This device exploits inertial fluidic effects that occur in a laminar regime at sufficiently high flow rates,manipulating the particle positions by the combination of inertial lift forces and Dean drag forces.The device is fabricated by femtosecond laser irradiation followed by chemical etching,which is a simple two-step process enabling the creation of 3D microfluidic networks in fused silica glass substrates.The use of tightly curving three-dimensional microfluidic loops produces strong Dean drag forces along the whole loop but also induces an asymmetric Dean flow decay in the subsequent straight channel,thus producing rapid cross-sectional mixing flows that assist with 3D particle focusing.The use of out-of-plane loops favors a compact parallelization of multiple focusing channels,allowing one to process large amounts of samples.In addition,the low fluidic resistance of the channel network is compatible with vacuum driven flows.The resulting device is quite interesting for high-throughput on-chip flow cytometry.
基金supported by the National Natural Science Foundation of China(Nos.61705027,62375031 and 52075131)the Chongqing Science and Technology Commission Basic Research Project(No.CSTC-2020jcyj-msxm0603)the Chongqing Municipal Education Commission Science and Technology Research Program(No.KJQN202000609)。
文摘To address the temperature cross-talk issue in detecting heavy metal ions in natural waters, a highly-integrated and fully fiber-optic metal ion sensing system capable of temperature-concentration decoupling measurement has been designed. This system integrates a fluidic detection structure assisted by side-polished fibers(SPFs) with a Sagnac interferometer.
