Activeow control technology is a technique that controls the internaloweld of aircraft engines or theoweld around wings by means of disturbances induced by actuators,and adjusts the aerodynamic force and attitude of t...Activeow control technology is a technique that controls the internaloweld of aircraft engines or theoweld around wings by means of disturbances induced by actuators,and adjusts the aerodynamic force and attitude of the aircraft,so as to achieve the purposes of increasing lift,reducing drag,suppressing vibration and reducing noise.Hailed as an important source of innovative development for aircraft,this technology provides a new technical approach to solve the aerodynamic problems of aircraft,signicantly improve their comprehensive performance,break throughight boundaries,and promote disruptive innovation in the next generation of aircraft.展开更多
A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi ＂Gl...A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi ＂Global Hawk＂ airfoil using arrays of jets during the gust process. Based on unsteady Navier-Stokes equations, the grid-velocity method is introduced to simulate the gust influence, and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well. An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil’s surface to emulate the time dependent velocity boundary conditions. Firstly, after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack, it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references. Furthermore, gust response characteristic for the quasi ＂Global Hawk＂ airfoil is analyzed. Five kinds of flow control techniques are introduced as steady blowing, steady suction, unsteady blowing, unsteady suction and synthetic jets. The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice. Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation, can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.展开更多
Ferrofluid moving thin films and their possible significance with regard to active flow control for lift and attack angle enhancement are discussed.In this strategy,a very thin film of ferrofluid is strongly attached ...Ferrofluid moving thin films and their possible significance with regard to active flow control for lift and attack angle enhancement are discussed.In this strategy,a very thin film of ferrofluid is strongly attached at the wall of the wing by a normal magnetic field from below and pumped tangentially along the wing.Utilizing a simplified physical model and from the available experimental data on moving walls,the expected lift enhancement and effect on the attack angle were assessed.Additional research and design is required in order to explore the possibilities in the use of ferrofluid moving thin films.展开更多
An intelligent wind tunnel using an active learning approach automates flow control experiments to discover the aerodynamic impact of sweeping jet on a swept wing. A Gaussian process regression model is established to...An intelligent wind tunnel using an active learning approach automates flow control experiments to discover the aerodynamic impact of sweeping jet on a swept wing. A Gaussian process regression model is established to study the jet actuator's performance at various attack and flap deflection angles. By selectively focusing on the most informative experiments, the proposed framework was able to predict 3721 wing conditions from just 55experiments, significantly reducing the number of experiments required and leading to faster and cost-effective predictions. The results show that the angle of attack and flap deflection angle are coupled to affect the effectiveness of the sweeping jet. Meanwhile, increasing the jet momentum coefficient can contribute to lift enhancement;a momentum coefficient of 3% can increase the lift coefficient by at most 0.28. Additionally, the improvement effects are more pronounced when actuators are placed closer to the wing root.展开更多
Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transduce...Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transducers fabrication.This paper introduces research works of MEMS/NEMS Lab in flow measurement sensors and active flow control actuators.Micro sensors include the flexible thermal sensor array,capacitive shear stress sensor and high sensitivity pressure sensor.Micro actuators are the balloon actuator and synthetic jet actuator respectively.Through wind tunnel test,these micro transducers achieve the goals of shear stress and pressure distribution measurement,boundary layer separation control,lift enhancement,etc.And unmanned aerial vehicle(UAV) flight test verifies the ability of maneuver control of micro actuator.In the future work,micro sensor and actuator can be combined into a closed-loop control system to construct aerodynamic smart skin system for aircraft.展开更多
Modern power systems increasingly depend on interconnected microgrids to enhance reliability and renewable energy utilization.However,the high penetration of intermittent renewable sources often causes frequency devia...Modern power systems increasingly depend on interconnected microgrids to enhance reliability and renewable energy utilization.However,the high penetration of intermittent renewable sources often causes frequency deviations,voltage fluctuations,and poor reactive power coordination,posing serious challenges to grid stability.Conventional Interconnection FlowControllers(IFCs)primarily regulate active power flowand fail to effectively handle dynamic frequency variations or reactive power sharing in multi-microgrid networks.To overcome these limitations,this study proposes an enhanced Interconnection Flow Controller(e-IFC)that integrates frequency response balancing and an Interconnection Reactive Power Flow Controller(IRFC)within a unified adaptive control structure.The proposed e-IFC is implemented and analyzed in DIgSILENT PowerFactory to evaluate its performance under various grid disturbances,including frequency drops,load changes,and reactive power fluctuations.Simulation results reveal that the e-IFC achieves 27.4% higher active power sharing accuracy,19.6% lower reactive power deviation,and 18.2% improved frequency stability compared to the conventional IFC.The adaptive controller ensures seamless transitions between grid-connected and islanded modes and maintains stable operation even under communication delays and data noise.Overall,the proposed e-IFCsignificantly enhances active-reactive power coordination and dynamic stability in renewable-integrated multi-microgrid systems.Future research will focus on coupling the e-IFC with tertiary-level optimization frameworks and conducting hardware-in-the-loop validation to enable its application in large-scale smart microgrid environments.展开更多
Passive-active control of a flexible isolation system is investigated from the viewpoint of power flow. Dynamic transfer equations of the system are deduced based on a matrix method which uses mobility or impedance re...Passive-active control of a flexible isolation system is investigated from the viewpoint of power flow. Dynamic transfer equations of the system are deduced based on a matrix method which uses mobility or impedance representations of three substructures: the source of vibration, the receiver and the mounting system which connects the source to the receiver. The cancellation of axial input forces to the receiver is considered as the active control strategy and its effects are discussed. The results of the study show that the strategy adopted herein can effectively reduce the power transmitted to the receiver.展开更多
Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are c...Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.展开更多
Microbubbles can enhance the detection in noninvasive ultrasound imaging.Recently,targeted microbubbles have been developed to selectively adhere to specific and overexpressed p molecules in endothelial cells in some ...Microbubbles can enhance the detection in noninvasive ultrasound imaging.Recently,targeted microbubbles have been developed to selectively adhere to specific and overexpressed p molecules in endothelial cells in some pathologic conditions.However,the law of展开更多
A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonance...A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.展开更多
The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(P...The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(PSJ)on double wedge type-Ⅵand type-ⅤSSI was investigated experimentally and numerically,and the influence of discharge energy was also explored.The findings indicate that the interaction between PSJ and the high-speed freestream results in the formation of a plasma layer and a jet shock,which collectively governs the control of SSI.The control mechanism of single-pulse PSJ on SSI lies in its capacity to attenuate both shock and SSI.For type-ⅥSSI,the original second-wedge oblique shock is eliminated under the control of PSJ,resulting in a new type-ⅥSSI formed by the jet shock and the first-wedge oblique shock.For type-ⅤSSI,the presence of PSJ effectively mitigates the intensity of Mach stem,supersonic jet,and reflected shocks,thereby facilitating its transition into type-ⅥSSI.The numerical results indicate that the peak pressure can be reduced by approximately 32.26%at maximum.Furthermore,the development of PSJ also extends in the Z direction.The pressure decreases in the area affected by both PSJ and jet shock due to the attenuation of the SSI zone.With increasing discharge energy,the control effect of PSJ on SSI is gradually enhanced.展开更多
Lateral flow assays(LFAs)are widely used in point-of-care testing(POCT)due to their simplicity and rapid operation.However,their reliance on passive capillary flow limits sensitivity,making it challenging to detect lo...Lateral flow assays(LFAs)are widely used in point-of-care testing(POCT)due to their simplicity and rapid operation.However,their reliance on passive capillary flow limits sensitivity,making it challenging to detect low-abundance biomarkers accurately.Approaches such as computer signal processing,chemical modification,and physical regulation have been explored to improve LFA sensitivity,but they remain limited by passive capillary-driven flow and uncontrollable flow rate.An alternative approach is to actively regulate fluid dynamics to optimize analyte binding and signal generation.The key challenge is to enhance LFA sensitivity while preserving compatibility with existing lateral flow strips(LFSs).Here,this study introduces a centrifugation-assisted LFA(CLFA)platform with smartphone-based result processing.This platform applies centrifugal force opposite to capillary flow,actively regulating fluid movement to optimize incubation time at the reaction zone and enhance detection performance.This approach increases signal intensity while maintaining a rapid detection process(5 min)and ensuring integration with traditional LFSs.As a proof-of-concept,the CLFA platform successfully detected human chorionic gonadotropin(hCG)and hemoglobin(Hb)in artificial urine without requiring custom-designed centrifugal discs or modified chromatography membranes.Its adaptability to diverse biomarkers and smartphone-based quantification make it a promising POCT tool,particularly in resource-limited settings.展开更多
With the development of low-noise aircraft engine, airframe noise now represents a major noise source during the commercial aircraft＇s approach to landing phase. Noise control efforts have therefore been extensively ...With the development of low-noise aircraft engine, airframe noise now represents a major noise source during the commercial aircraft＇s approach to landing phase. Noise control efforts have therefore been extensively focused on the airframe noise problems in order to further reduce aircraft overall noise. In this review, various control methods explored in the last decades for noise reduction on airframe components including high-lift devices and landing gears are summarized. We introduce recent major achievements in airframe noise reduction with passive control methods such as fairings, deceleration plates, splitter plates, acoustic liners, slat cove cover and side-edge replacements, and then discuss the potential and control mechanism of some promising active flow control strategies for airframe noise reduction, such as plasma technique and air blowing/suction devices. Based on the knowledge gained throughout the extensively noise control testing, a few design concepts on the landing gear, high-lift devices and whole aircraft are provided for advanced aircraft low-noise design. Finally, discussions and suggestions are given for future research on airframe noise reduction.展开更多
Circulation Control(CC) realizes rudderless flight control by driving compressed air jet to generate a virtual rudder surface, which significantly improves low detectability. The layout plan of combined control rudder...Circulation Control(CC) realizes rudderless flight control by driving compressed air jet to generate a virtual rudder surface, which significantly improves low detectability. The layout plan of combined control rudder surface is proposed based on the tailless flying wing aircraft. The closed-loop jet actuator system and stepless rudder surface switching control strategy are used to quantitatively study the control characteristics of circulation actuator for pitch and roll attitude through 3-DOF virtual flight test in a wind tunnel with a powered model at wind speed of 40 m/s. The results show that the combined use of circulation actuators can achieve bidirectional continuous and stable control of the aircraft’s pitch and roll attitude, with the maximum pitch rate of 12.3(°)/s and the maximum roll rate of 21.5(°)/s;the response time of attitude angular rate varying with the jet pressure ratio is less than 0.02 s, which can satisfy the control response requirements of aircraft motion stability for the control system;the jet rudder surface has a strong moment control ability, and the pitch moment of the jet elevator with a pressure ratio of 1.28 is the same as that of the mechanical elevator with 28° rudder deflection, which can expand the flight control boundary.展开更多
Numerical investigations are conducted to explore the aerodynamic characteristics of three-dimensional Co-Flow Jet(CFJ) wing with simple high-lift devices during low-speed takeoff and landing. Effects of three crucial...Numerical investigations are conducted to explore the aerodynamic characteristics of three-dimensional Co-Flow Jet(CFJ) wing with simple high-lift devices during low-speed takeoff and landing. Effects of three crucial parameters of CFJ wing, i.e., angle of attack, jet momentum and swept angle, are comprehensively examined. Additionally, the aerodynamic characteristics of two CFJ configurations, i.e., using open and discrete slots for injection, are compared. The results show that applying CFJ technique to a wing with simple high-lift device is able to generate more lift,reduce drag and enlarge stall margin with lower energy expenditure due to the super-circulation effect. Increasing the jet intensity can reduce the drag significantly, which is mainly contributed by the reaction jet force. The Oswald efficiency factor is, in some circumstances, larger than one,which indicates the potential of CFJ in reducing induced drag. Compared with clean wing configuration, using CFJ technique allows the aerodynamic force variation less sensitive to the swept angle, and such phenomenon is better observed for small swept angle region. Eventually, it is interesting to know that the discrete slotted CFJ configuration demonstrates a promising enhancement in aerodynamic performance in terms of high lift, low drag and efficiency.展开更多
Both the Active Flow Control(AFC)and the variable-camber technology are considered as efficient ways to enhance the aerodynamic performance of an aircraft.The present study investigated the feasibility of the combinat...Both the Active Flow Control(AFC)and the variable-camber technology are considered as efficient ways to enhance the aerodynamic performance of an aircraft.The present study investigated the feasibility of the combination of a Co-Flow Jet(CFJ)airfoil and a parabolic flap,where the Reynolds Average Navier-Stokes(RANS)equations and the Spalart-Allmaras(S-A)turbulence model were exploited for the numerical simulation.Several significant geometric parameters,including the injection slot location,the suction slot location,the injection slot angle,the suction slot angle and the airfoil Suction Surface Translation(SST),were selected to study their effects on the aerodynamics of the proposed configuration.Then,an optimized design was created and compared with the baseline airfoil.The results show that the CFJ airfoil combined with the parabolic flap is more beneficial to the aerodynamic performance enhancement at small angles of attack.It is preferable to locate the injection slot at a 2%chord-wise location and the suction slot at a 75%chord-wise location.Both the decrease of the injection slot angle and the augmentation of the suction slot angle could reduce the drag.Furthermore,the SST of 0.5%chord is selected due to its high gain in the corrected aerodynamic efficiency at small angles of attack.Compared with the baseline,the optimized design could increase the lift coefficient and the corrected lift-to-drag ratio by 32.1%and 93.8%respectively at the angle of attack a=4°.展开更多
While dielectric-barrier-discharge(DBD)based plasma actuation systems have been successfully demonstrated to suppress massive flow separation over wind turbine blades to reduce the transient aerodynamic loadings actin...While dielectric-barrier-discharge(DBD)based plasma actuation systems have been successfully demonstrated to suppress massive flow separation over wind turbine blades to reduce the transient aerodynamic loadings acting on the turbine blades,it is still a non-trivial task to establish a best combination of various operating parameters for a DBD plasma actuation system to achieve the optimized flow control effectiveness.In the present study,a regression Kriging based metamodeling technique is developed to optimize the operating parameters of a DBD plasma actuation system for suppressing deep stall over the surface of a wind turbine blade section/airfoil model.The data points were experimentally obtained by embedding a nanosecond-pulsed DBD(NS-DBD)plasma actuator at the leading edge of the airfoil model.The applied voltage and frequency for the NS-DBD plasma actuation were used as the design variables to demonstrate the optimization procedure.The highest possible lift coefficient of the turbine airfoil model at deep stalled angles of attack(i.e.,α?=?22°and 24°)were selected as the objective function for the optimization.It was found that,while the metamodeling-based procedure could accurately predict the objective function within the bounds of the design variables with an uncertainty~?2%,a global accuracy level of~?97%was achieved within the whole design space.展开更多
Actuators are one of the key points for the development of active flow control technology.Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and ma...Actuators are one of the key points for the development of active flow control technology.Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and maneuverable high speed flight.The development of high speed flight technology promotes the emergence of novel and robust actuators.This review introduces the state of the art in the development of actuators that can be used in high speed active flow control.The classification and different operation criteria of the actuators are discussed.The specifications,mechanisms and applications of various popular actuator types including fluidic,mechanical,and plasma actuators are described.Based on the realistic need of high speed flow control and the existing results of actuators,a new actuator design method is proposed.At last,the merits and drawbacks of the actuators are summarized and some suggestions on the development of active flow control technology are put forward.展开更多
Nowadays the rapidly developing artificial intelligence has become a key solution for problems of diverse disciplines,especially those involving big data.Successes in these areas also attract researchers from the comm...Nowadays the rapidly developing artificial intelligence has become a key solution for problems of diverse disciplines,especially those involving big data.Successes in these areas also attract researchers from the community of fluid mechanics,especially in the field of active flow control(AFC).This article surveys recent successful applications of machine learning in AFC,highlights general ideas,and aims at offering a basic outline for those who are interested in this specific topic.In this short review,we focus on two methodologies,i.e.,genetic programming(GP)and deep reinforcement learning(DRL),both having been proven effective,efficient,and robust in certain AFC problems,and outline some future prospects that might shed some light for relevant studies.展开更多
Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is...Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is discussed in this paper,including blowing momentum and circumferential locations of the microblowing hole of 0.5 mm in diameter on nose tip.A new kind of active control technique,named perturbation-combined active control technique,which combines the micro-grain and micro-blowing perturbation,was proposed on the basis of the above.This control technique can not only change the sign of side force of slender body arbitrarily through changing the vortices positions between yaw-left and yaw-right configuration,but also can make the magnitude of side force variable gradually even at bistable state of asymmetric vortex.Finally,the interferential mechanism of the perturbation-combined active control technique has also been concluded from this paper.The tests have been conducted at low speed wind tunnel with subcritical Reynolds number of 1.05×10~5 at angle of attack α=50° in Beihang University,Beijing,China.展开更多
文摘Activeow control technology is a technique that controls the internaloweld of aircraft engines or theoweld around wings by means of disturbances induced by actuators,and adjusts the aerodynamic force and attitude of the aircraft,so as to achieve the purposes of increasing lift,reducing drag,suppressing vibration and reducing noise.Hailed as an important source of innovative development for aircraft,this technology provides a new technical approach to solve the aerodynamic problems of aircraft,signicantly improve their comprehensive performance,break throughight boundaries,and promote disruptive innovation in the next generation of aircraft.
文摘A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi ＂Global Hawk＂ airfoil using arrays of jets during the gust process. Based on unsteady Navier-Stokes equations, the grid-velocity method is introduced to simulate the gust influence, and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well. An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil’s surface to emulate the time dependent velocity boundary conditions. Firstly, after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack, it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references. Furthermore, gust response characteristic for the quasi ＂Global Hawk＂ airfoil is analyzed. Five kinds of flow control techniques are introduced as steady blowing, steady suction, unsteady blowing, unsteady suction and synthetic jets. The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice. Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation, can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.
基金supported by the Spanish Ministry of Economy and Competitiveness under Fellowship Grant Ramon y Cajal(No.RYC-2013-13459)。
文摘Ferrofluid moving thin films and their possible significance with regard to active flow control for lift and attack angle enhancement are discussed.In this strategy,a very thin film of ferrofluid is strongly attached at the wall of the wing by a normal magnetic field from below and pumped tangentially along the wing.Utilizing a simplified physical model and from the available experimental data on moving walls,the expected lift enhancement and effect on the attack angle were assessed.Additional research and design is required in order to explore the possibilities in the use of ferrofluid moving thin films.
基金supported by the National Natural Science Foundation of China (Grant No.92271107)。
文摘An intelligent wind tunnel using an active learning approach automates flow control experiments to discover the aerodynamic impact of sweeping jet on a swept wing. A Gaussian process regression model is established to study the jet actuator's performance at various attack and flap deflection angles. By selectively focusing on the most informative experiments, the proposed framework was able to predict 3721 wing conditions from just 55experiments, significantly reducing the number of experiments required and leading to faster and cost-effective predictions. The results show that the angle of attack and flap deflection angle are coupled to affect the effectiveness of the sweeping jet. Meanwhile, increasing the jet momentum coefficient can contribute to lift enhancement;a momentum coefficient of 3% can increase the lift coefficient by at most 0.28. Additionally, the improvement effects are more pronounced when actuators are placed closer to the wing root.
基金National Natural Science Foundation of China (No. 90305017No. 50775188No. 51105317)
文摘Advanced flow measurement and active flow control need the development of new type devices and systems.Micro-electro-mechanical systems(MEMS) technologies become the important and feasible approach for micro transducers fabrication.This paper introduces research works of MEMS/NEMS Lab in flow measurement sensors and active flow control actuators.Micro sensors include the flexible thermal sensor array,capacitive shear stress sensor and high sensitivity pressure sensor.Micro actuators are the balloon actuator and synthetic jet actuator respectively.Through wind tunnel test,these micro transducers achieve the goals of shear stress and pressure distribution measurement,boundary layer separation control,lift enhancement,etc.And unmanned aerial vehicle(UAV) flight test verifies the ability of maneuver control of micro actuator.In the future work,micro sensor and actuator can be combined into a closed-loop control system to construct aerodynamic smart skin system for aircraft.
基金the Deanship of Scientific Research at Northern Border University,Arar,Saudi Arabia,for funding this research work through the project number“NBU-FFR-2025-3623-11”.
文摘Modern power systems increasingly depend on interconnected microgrids to enhance reliability and renewable energy utilization.However,the high penetration of intermittent renewable sources often causes frequency deviations,voltage fluctuations,and poor reactive power coordination,posing serious challenges to grid stability.Conventional Interconnection FlowControllers(IFCs)primarily regulate active power flowand fail to effectively handle dynamic frequency variations or reactive power sharing in multi-microgrid networks.To overcome these limitations,this study proposes an enhanced Interconnection Flow Controller(e-IFC)that integrates frequency response balancing and an Interconnection Reactive Power Flow Controller(IRFC)within a unified adaptive control structure.The proposed e-IFC is implemented and analyzed in DIgSILENT PowerFactory to evaluate its performance under various grid disturbances,including frequency drops,load changes,and reactive power fluctuations.Simulation results reveal that the e-IFC achieves 27.4% higher active power sharing accuracy,19.6% lower reactive power deviation,and 18.2% improved frequency stability compared to the conventional IFC.The adaptive controller ensures seamless transitions between grid-connected and islanded modes and maintains stable operation even under communication delays and data noise.Overall,the proposed e-IFCsignificantly enhances active-reactive power coordination and dynamic stability in renewable-integrated multi-microgrid systems.Future research will focus on coupling the e-IFC with tertiary-level optimization frameworks and conducting hardware-in-the-loop validation to enable its application in large-scale smart microgrid environments.
基金National Natural Science Foundation of China (No.50275085)
文摘Passive-active control of a flexible isolation system is investigated from the viewpoint of power flow. Dynamic transfer equations of the system are deduced based on a matrix method which uses mobility or impedance representations of three substructures: the source of vibration, the receiver and the mounting system which connects the source to the receiver. The cancellation of axial input forces to the receiver is considered as the active control strategy and its effects are discussed. The results of the study show that the strategy adopted herein can effectively reduce the power transmitted to the receiver.
基金co-supported by the Postdoctoral Foundation of China (Nos. 2013M542525, 2014T71019)
文摘Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.
基金supported by National Natural Science Foundation of China,No.30700151
文摘Microbubbles can enhance the detection in noninvasive ultrasound imaging.Recently,targeted microbubbles have been developed to selectively adhere to specific and overexpressed p molecules in endothelial cells in some pathologic conditions.However,the law of
基金This project is supported by Commission of Science Technology and Industry for National Defense, China.
文摘A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.
基金supported by the Independent Innovation Science Fund of National University of Defense Technology(No.24-ZZCX-BC-05)National Natural Science Foundation of China(Nos.92271110 and 12202488)+2 种基金the Major National Science and Technology Project(No.J2019-Ⅲ0010-0054)the National Postdoctoral Researcher Program of China(No.GZB20230985)the Natural Science Program of National University of Defense Technology(No.ZK22-30)。
文摘The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(PSJ)on double wedge type-Ⅵand type-ⅤSSI was investigated experimentally and numerically,and the influence of discharge energy was also explored.The findings indicate that the interaction between PSJ and the high-speed freestream results in the formation of a plasma layer and a jet shock,which collectively governs the control of SSI.The control mechanism of single-pulse PSJ on SSI lies in its capacity to attenuate both shock and SSI.For type-ⅥSSI,the original second-wedge oblique shock is eliminated under the control of PSJ,resulting in a new type-ⅥSSI formed by the jet shock and the first-wedge oblique shock.For type-ⅤSSI,the presence of PSJ effectively mitigates the intensity of Mach stem,supersonic jet,and reflected shocks,thereby facilitating its transition into type-ⅥSSI.The numerical results indicate that the peak pressure can be reduced by approximately 32.26%at maximum.Furthermore,the development of PSJ also extends in the Z direction.The pressure decreases in the area affected by both PSJ and jet shock due to the attenuation of the SSI zone.With increasing discharge energy,the control effect of PSJ on SSI is gradually enhanced.
基金financial support from the programs of the Natural Science Foundation of the Jiangsu Higher Education(24KJB460030)XJTLU RDF project(RDF-21-02-076)+4 种基金partially supported by the XJTLU AI University Research Centre,Jiangsu Province Engineering Research Centre of Data Science and Cognitive Computation at XJTLUthe SIP AI innovation platform(YZCXPT2022103)Jiangsu Provincial Outstanding Youth Program(BK20230072)Suzhou Industrial Foresight and Key Core Technology Project(SYC2022044)grants from Jiangsu QingLan Project and Jiangsu 333 high-level talents.
文摘Lateral flow assays(LFAs)are widely used in point-of-care testing(POCT)due to their simplicity and rapid operation.However,their reliance on passive capillary flow limits sensitivity,making it challenging to detect low-abundance biomarkers accurately.Approaches such as computer signal processing,chemical modification,and physical regulation have been explored to improve LFA sensitivity,but they remain limited by passive capillary-driven flow and uncontrollable flow rate.An alternative approach is to actively regulate fluid dynamics to optimize analyte binding and signal generation.The key challenge is to enhance LFA sensitivity while preserving compatibility with existing lateral flow strips(LFSs).Here,this study introduces a centrifugation-assisted LFA(CLFA)platform with smartphone-based result processing.This platform applies centrifugal force opposite to capillary flow,actively regulating fluid movement to optimize incubation time at the reaction zone and enhance detection performance.This approach increases signal intensity while maintaining a rapid detection process(5 min)and ensuring integration with traditional LFSs.As a proof-of-concept,the CLFA platform successfully detected human chorionic gonadotropin(hCG)and hemoglobin(Hb)in artificial urine without requiring custom-designed centrifugal discs or modified chromatography membranes.Its adaptability to diverse biomarkers and smartphone-based quantification make it a promising POCT tool,particularly in resource-limited settings.
文摘With the development of low-noise aircraft engine, airframe noise now represents a major noise source during the commercial aircraft＇s approach to landing phase. Noise control efforts have therefore been extensively focused on the airframe noise problems in order to further reduce aircraft overall noise. In this review, various control methods explored in the last decades for noise reduction on airframe components including high-lift devices and landing gears are summarized. We introduce recent major achievements in airframe noise reduction with passive control methods such as fairings, deceleration plates, splitter plates, acoustic liners, slat cove cover and side-edge replacements, and then discuss the potential and control mechanism of some promising active flow control strategies for airframe noise reduction, such as plasma technique and air blowing/suction devices. Based on the knowledge gained throughout the extensively noise control testing, a few design concepts on the landing gear, high-lift devices and whole aircraft are provided for advanced aircraft low-noise design. Finally, discussions and suggestions are given for future research on airframe noise reduction.
基金supported by the Equipment Pre-research Common Technology Project,China(No.41406010101).
文摘Circulation Control(CC) realizes rudderless flight control by driving compressed air jet to generate a virtual rudder surface, which significantly improves low detectability. The layout plan of combined control rudder surface is proposed based on the tailless flying wing aircraft. The closed-loop jet actuator system and stepless rudder surface switching control strategy are used to quantitatively study the control characteristics of circulation actuator for pitch and roll attitude through 3-DOF virtual flight test in a wind tunnel with a powered model at wind speed of 40 m/s. The results show that the combined use of circulation actuators can achieve bidirectional continuous and stable control of the aircraft’s pitch and roll attitude, with the maximum pitch rate of 12.3(°)/s and the maximum roll rate of 21.5(°)/s;the response time of attitude angular rate varying with the jet pressure ratio is less than 0.02 s, which can satisfy the control response requirements of aircraft motion stability for the control system;the jet rudder surface has a strong moment control ability, and the pitch moment of the jet elevator with a pressure ratio of 1.28 is the same as that of the mechanical elevator with 28° rudder deflection, which can expand the flight control boundary.
基金the National Natural Science Foundation of China (No. 11672133)the Fundamental Research Funds for the Central Universities, China (No. kfjj20180104)support from Rotor Aerodynamics Key Laboratory, China (No. RAL20190202-2/RAL20190101-1)
文摘Numerical investigations are conducted to explore the aerodynamic characteristics of three-dimensional Co-Flow Jet(CFJ) wing with simple high-lift devices during low-speed takeoff and landing. Effects of three crucial parameters of CFJ wing, i.e., angle of attack, jet momentum and swept angle, are comprehensively examined. Additionally, the aerodynamic characteristics of two CFJ configurations, i.e., using open and discrete slots for injection, are compared. The results show that applying CFJ technique to a wing with simple high-lift device is able to generate more lift,reduce drag and enlarge stall margin with lower energy expenditure due to the super-circulation effect. Increasing the jet intensity can reduce the drag significantly, which is mainly contributed by the reaction jet force. The Oswald efficiency factor is, in some circumstances, larger than one,which indicates the potential of CFJ in reducing induced drag. Compared with clean wing configuration, using CFJ technique allows the aerodynamic force variation less sensitive to the swept angle, and such phenomenon is better observed for small swept angle region. Eventually, it is interesting to know that the discrete slotted CFJ configuration demonstrates a promising enhancement in aerodynamic performance in terms of high lift, low drag and efficiency.
基金supported by the National Natural Science Foundation of China(Nos.12102431,12002340,and 11902320).
文摘Both the Active Flow Control(AFC)and the variable-camber technology are considered as efficient ways to enhance the aerodynamic performance of an aircraft.The present study investigated the feasibility of the combination of a Co-Flow Jet(CFJ)airfoil and a parabolic flap,where the Reynolds Average Navier-Stokes(RANS)equations and the Spalart-Allmaras(S-A)turbulence model were exploited for the numerical simulation.Several significant geometric parameters,including the injection slot location,the suction slot location,the injection slot angle,the suction slot angle and the airfoil Suction Surface Translation(SST),were selected to study their effects on the aerodynamics of the proposed configuration.Then,an optimized design was created and compared with the baseline airfoil.The results show that the CFJ airfoil combined with the parabolic flap is more beneficial to the aerodynamic performance enhancement at small angles of attack.It is preferable to locate the injection slot at a 2%chord-wise location and the suction slot at a 75%chord-wise location.Both the decrease of the injection slot angle and the augmentation of the suction slot angle could reduce the drag.Furthermore,the SST of 0.5%chord is selected due to its high gain in the corrected aerodynamic efficiency at small angles of attack.Compared with the baseline,the optimized design could increase the lift coefficient and the corrected lift-to-drag ratio by 32.1%and 93.8%respectively at the angle of attack a=4°.
基金the National Science Foundation(NSF)(Grants OISE-1826978 and CBET-1916380).
文摘While dielectric-barrier-discharge(DBD)based plasma actuation systems have been successfully demonstrated to suppress massive flow separation over wind turbine blades to reduce the transient aerodynamic loadings acting on the turbine blades,it is still a non-trivial task to establish a best combination of various operating parameters for a DBD plasma actuation system to achieve the optimized flow control effectiveness.In the present study,a regression Kriging based metamodeling technique is developed to optimize the operating parameters of a DBD plasma actuation system for suppressing deep stall over the surface of a wind turbine blade section/airfoil model.The data points were experimentally obtained by embedding a nanosecond-pulsed DBD(NS-DBD)plasma actuator at the leading edge of the airfoil model.The applied voltage and frequency for the NS-DBD plasma actuation were used as the design variables to demonstrate the optimization procedure.The highest possible lift coefficient of the turbine airfoil model at deep stalled angles of attack(i.e.,α?=?22°and 24°)were selected as the objective function for the optimization.It was found that,while the metamodeling-based procedure could accurately predict the objective function within the bounds of the design variables with an uncertainty~?2%,a global accuracy level of~?97%was achieved within the whole design space.
基金supported by the National Natural Science Foundation of China (Grant No. 11002161)the Foundation for the Author of National Excellent Doctor Dissertation of China (Grant No. 201058)the Specialized Research Fund for the Doctor Program of Higher Education of China (Grant No. 20104307110007)
文摘Actuators are one of the key points for the development of active flow control technology.Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and maneuverable high speed flight.The development of high speed flight technology promotes the emergence of novel and robust actuators.This review introduces the state of the art in the development of actuators that can be used in high speed active flow control.The classification and different operation criteria of the actuators are discussed.The specifications,mechanisms and applications of various popular actuator types including fluidic,mechanical,and plasma actuators are described.Based on the realistic need of high speed flow control and the existing results of actuators,a new actuator design method is proposed.At last,the merits and drawbacks of the actuators are summarized and some suggestions on the development of active flow control technology are put forward.
基金This work was support by the Research Grants Council of Hong Kong under General Research Fund(Grant Nos.15249316,15214418)the Departmental General Research Fund(Grant No.G-YBXQ).
文摘Nowadays the rapidly developing artificial intelligence has become a key solution for problems of diverse disciplines,especially those involving big data.Successes in these areas also attract researchers from the community of fluid mechanics,especially in the field of active flow control(AFC).This article surveys recent successful applications of machine learning in AFC,highlights general ideas,and aims at offering a basic outline for those who are interested in this specific topic.In this short review,we focus on two methodologies,i.e.,genetic programming(GP)and deep reinforcement learning(DRL),both having been proven effective,efficient,and robust in certain AFC problems,and outline some future prospects that might shed some light for relevant studies.
基金supported by the National Natural Science Foundation of China (Grant No. 10872019)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20101102110015),NCET-06-0176
文摘Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is discussed in this paper,including blowing momentum and circumferential locations of the microblowing hole of 0.5 mm in diameter on nose tip.A new kind of active control technique,named perturbation-combined active control technique,which combines the micro-grain and micro-blowing perturbation,was proposed on the basis of the above.This control technique can not only change the sign of side force of slender body arbitrarily through changing the vortices positions between yaw-left and yaw-right configuration,but also can make the magnitude of side force variable gradually even at bistable state of asymmetric vortex.Finally,the interferential mechanism of the perturbation-combined active control technique has also been concluded from this paper.The tests have been conducted at low speed wind tunnel with subcritical Reynolds number of 1.05×10~5 at angle of attack α=50° in Beihang University,Beijing,China.
