We propose a novel cooling protocol within a triple-Laguerre-Gaussian cavity optomechanical system,which is designed to suppress the thermal vibrations of a rotating mirror to reach its quantum ground state.The system...We propose a novel cooling protocol within a triple-Laguerre-Gaussian cavity optomechanical system,which is designed to suppress the thermal vibrations of a rotating mirror to reach its quantum ground state.The system incorporates two auxiliary cavities and an atomic ensemble coupled to a Laguerre-Gaussian rotational cavity.By carefully selecting system parameters,the cooling process of the rotating mirror is significantly enhanced,while the heating process is effectively suppressed,enabling efficient ground-state cooling even in the unresolved sideband regime.Compared to previous works,our scheme reduces the stringent restrictions on auxiliary systems,making it more experimentally feasible under broader parameter conditions.These findings provide a robust approach for achieving ground-state cooling in mechanical resonators.展开更多
We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating sli...We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating slit mechanism,a 3D symmetric spherical focal field distribution is created in the laser-irradiated regions of transparent substrates.The corresponding focal field distribution is theoretically calculated and validated by examining the features of laser-inscribed lines in glass samples.Moreover,we investigate the influences of laser writing speed and slit rotational speed on the fabrication resolution in glass,and discuss the formation mechanism of the generated periodic microstructures.To showcase its powerful capability for3D isotropic fabrication,the high-speed rotating slit beam shaping method is applied to create straight optical waveguides,bending optical waveguides,and hollow microchannels in the glass.The proposed method holds great potential for the facile manufacture of diverse 3D isotropic microstructures and devices within transparent materials across various applications,including advanced photonics,microoptics,micro-electromechanical systems,and microfluidics.展开更多
As a type of emerging electro-mechanical conversion technology,triboelectric nanogenerators(TENGs)were widely applied in high-entropy energy harvesting,Internet of Things sensing,and biomedical fields due to the chara...As a type of emerging electro-mechanical conversion technology,triboelectric nanogenerators(TENGs)were widely applied in high-entropy energy harvesting,Internet of Things sensing,and biomedical fields due to the characteristics of lightweight,cheap,and high voltage.Among them,the rotating TENG has been extensively researched for its advantages,such as high-precision electrical signals,high electro-mechanical conversion efficiency,and effective output power.In this paper,the working mechanisms of four different rotating TENG modes were introduced in detail.Subsequently,a large amount of research works on the strengthening performance of rotating TENGs were comprehensively introduced and summarized by three gradient classifications.In addition,in view of the many applications of rotating TENGs,they were also systematically divided and generalized into three dimensions.Finally,the problems as well as challenges faced by the current rotating TENG research in the above 16 specific research directions were deeply analyzed,and the possible development directions and the solutions to the above problems were reasonably prospected in the next years.This review hopes to effectively promote the progress of rotating TENG on the road to commercialization.展开更多
In this paper,we study the issue of controlling a rotating flexible body-beam system(RFBBS)which consists of a tip mass attached to the free-end and a rigid disk attached to the clamped-end of an Euler-Bernoulli beam....In this paper,we study the issue of controlling a rotating flexible body-beam system(RFBBS)which consists of a tip mass attached to the free-end and a rigid disk attached to the clamped-end of an Euler-Bernoulli beam.The boundary control input is affected by both unknown disturbance and nonlinear input backlash.First,the input backlash is considered as desired control input combined with a nonlinear input error,converting it to an external disturbance,and then,the control signal is designed through the energy-based control method.Next,the closed-loop system’s stability is analysed through Lyapunov direct method.Finally,the efficacy of the proposed control scheme is tested through numerical simulations utilizing the finite difference method.展开更多
Rotating Single-Baseline Interferometer(RSBI)systems have attracted considerable attention for Direct Position Determination(DPD)due to their simplicity and high localization accuracy.Nevertheless,the growing complexi...Rotating Single-Baseline Interferometer(RSBI)systems have attracted considerable attention for Direct Position Determination(DPD)due to their simplicity and high localization accuracy.Nevertheless,the growing complexity of electromagnetic environments has led to scenarios with multiple time-frequency aliased sources,rendering conventional DPD methods for RSBI systems ineffective.Previous studies have predominantly concentrated on deploying antenna arrays and applying related signal-processing techniques for localization.Typically,these approaches necessitate that the number of physical antennas exceeds the number of sources.For RSBI systems already in practical operation,this would entail the installation of additional physical antennas,which implies equipment recycling and hardware upgrades.In numerous cases,such modifications are unfeasible.This paper proposes a novel Relative Offset-based Direct Position Determination(RO-DPD)method for RSBI systems that can handle multiple time-frequency aliased sources.The proposed method overcomes the challenge of simultaneous positioning without requiring hardware modifications by leveraging time accumulation and algorithmic enhancements.The implementation of the method involves three key steps.Firstly,the rotation of the interferometer is synthesized into a virtual Uniform Circular Array(UCA).Secondly,a novel estimation variable,termed relative offset,is introduced.The variable serves as an intermediate parameter to establish correlation equations between the positions of multiple time-frequency aliased sources and the intercepted signals.Thirdly,the relative offset model in the UCA is transformed into a virtual Uniform Linear Array(ULA)model,from which the cost function can be derived via the Spatial Smoothing(SS)MUSIC algorithm.Theoretical analysis and simulation results verify the effectiveness of the proposed method.Compared with traditional approaches,the RO-DPD method maintains the low complexity of RSBI systems while demonstrating robust performance in complex electromagnetic environments.展开更多
Existing nanogenerator technologies for harvesting high-power energy from wind encounter significant chal-lenges due to limitations in current output.Here,we propose a rotating-switch triboelectric nanogenerator(RS-TE...Existing nanogenerator technologies for harvesting high-power energy from wind encounter significant chal-lenges due to limitations in current output.Here,we propose a rotating-switch triboelectric nanogenerator(RS-TENG)that uses mechanical triggering switches(on-off-on)to enhance the instantaneous current pulses during rotation.The rotating-switch in the proposed device addresses the issue of low instantaneous current output in triboelectric nanogenerators while maintaining voltage stability.At a constant rotational speed,the RS-TENG achieves an instantaneous current of 3.2 times that of its nonswitching counterpart,with an 89%reduction in response time.Furthermore,at a wind speed of 2 m·s^(-1),the RS-TENG achieves a wind power density of 10.4 mW·m^(-2)·m^(-1)·s.Additionally,by integrating the RS-TENG with energy management circuits,the nanogenerator can power wireless signal transmitters and temperature sensors,offering a self-sustaining power solution for remote wireless services.This research presents a promising technology for powering electronic devices in energy-scarce environments.展开更多
Thermal vibrational convection(TVC)refers to the time-averaged convection of a non-isothermal fluid subjected to oscillating force fields.It serves as an effective mechanism for heat transfer control,particularly unde...Thermal vibrational convection(TVC)refers to the time-averaged convection of a non-isothermal fluid subjected to oscillating force fields.It serves as an effective mechanism for heat transfer control,particularly under microgravity conditions.A key challenge in this field is understanding the effect of rotation on TVC,as fluid oscillations in rotating systems exhibit unique and specific characteristics.In this study,we examine TVC in a vertical flat layer with boundaries at different temperatures,rotating around a horizontal axis.The distinctive feature of this study is that the fluid oscillations within the cavity are not induced by vibrations of the cavity itself,but rather by the gravity field,giving them a tidal nature.Our findings reveal that inertial waves generated in the rotating layer qualitatively alter the TVC structure,producing time-averaged flows in the form of toroidal vortices.Experimental investigations of the structure of oscillatory and time-averaged flows,conducted using Particle Image Velocimetry(PIV)for flow velocity visualization,are complemented by theoretical calculations of inertial modes in a cavity with this geometry.To the best of our knowledge,this study represents the first of its kind.The agreement between experimental results and theoretical predictions confirms that the formation of convective structures in the form of toroidal vortices is driven by inertial waves induced by the gravity field.A decrease in the rotational velocity leads to a transformation of the convective structures,shifting from toroidal vortices of inertial-wave origin to classical cellular TVC.We present dimensionless parameters that define the excitation thresholds for both cellular convection and toroidal structures.展开更多
The purpose of this study was to evaluate the clinical application of a rotating pod and assess its dosimetric considerations,positional accuracy,and anatomical structure stability.A pre-dosimetric study conducted on ...The purpose of this study was to evaluate the clinical application of a rotating pod and assess its dosimetric considerations,positional accuracy,and anatomical structure stability.A pre-dosimetric study conducted on 11 patients revealed the potential for lung dose reduction using the rotational pod.Subsequently,seven patients underwent treatment with the rotational pod,and the target coverage and organs at risk doses were compared with those of conventional methods.The positional accuracy of the rotational pod,in collaboration with the imaging guidance system,was analyzed.The Dice similarity coefficient(DSC)was used to assess the settlement of tumors,trachea,and thoracic vertebrae after rotation for 20 min.In the pre-dosimetric study,there was no statistically significant difference in the volume of the internal gross tumor volume receiving≥99%of the prescription dose between the pod and conventional couch plans.However,compared to conventional couch plans,pod plans demonstrated a significant reduction in the average lung dose by 5-53%(p<0.01).Patient accrual,comprising seven cases,revealed reduced lung doses(9-26%)in four patients.For the other three patients,although there was no significant reduction in the lung dose,the use of the 90°beamline contributed to a decrease in the patient admission waiting time.The positional errors between the beams for lateral,longitudinal,vertical,ISO,pitch,and roll directions were 0.0 mm±5.3 mm,-1.2 mm±2.3 mm,-1.1 mm±2.7 mm,0.0°±0.6°,-0.1°±0.5°,and 0.0°±0.8°,respectively.The DSC for the target region and thoracic vertebrae between CT images captured before and after a 20-min rotation was higher than 0.85,whereas the DSC for the trachea was approximately 0.8.The preliminary clinical application of the rotational pod for lung tumors in fixed ion beamlines shows promise for achieving target coverage,reducing lung dose,and maintaining position accuracy.展开更多
In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The e...In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.展开更多
Rotating machinery is critical to industrial systems,necessitating robust anomaly detection(AD)to ensure operational safety and prevent failures.However,in real-world scenarios,monitoring data is typically unlabeled a...Rotating machinery is critical to industrial systems,necessitating robust anomaly detection(AD)to ensure operational safety and prevent failures.However,in real-world scenarios,monitoring data is typically unlabeled and often consists of normal samples contaminated with a small proportion of unknown anomalies.To address this,this paper proposes a diffusion-based AD method,Anomaly Detection Denoising Diffusion Probabilistic Model(AD-DDPM)for robust AD.The method employs a U-attention-net to capture local and global features and introduces a filtered contrastive mechanism to mitigate the impact of contaminated training data.By leveraging the probabilistic nature of diffusion models,AD-DDPM effectively models normal data distributions,achieving superior AD even with polluted samples.Experimental validation on fault simulation datasets demonstrates the method’s exceptional performance,outperforming traditional machine learning and deep learning baselines.The proposed approach offers a promising solution for reliable health monitoring in industrial settings.展开更多
This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and...This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.展开更多
Odd elasticity introduces active moduli to the antisymmetric components of the elastic tensor,which describe the asymmetric coupling between different deformation modes in a medium and quantify the work extracted duri...Odd elasticity introduces active moduli to the antisymmetric components of the elastic tensor,which describe the asymmetric coupling between different deformation modes in a medium and quantify the work extracted during quasi-static strain cycles.The introduction of active moduli renders the elastic tensor non-Hermitian,breaking the Maxwell-Betti reciprocity and enabling the observation of phenomena that cannot occur in traditional passive media.Here,we develop an analytical dynamic model for odd elastic circular plates to investigate the effects of odd elasticity on motion in rotationally symmetric geometries.We report a novel nonreciprocal rotating wave and explore the effects of different odd elastic moduli on chiral deformation.Nonreciprocal rotating waves represent a distinct dynamic mode,exhibiting unidirectional propagation with amplitude increasing or decreasing exclusively along a specific direction.The amplitude change during motion reveals the system’s non-conservation of energy.展开更多
The dynamics of fluid and non-buoyant particles in a librating horizontal annulus is studied experimentally.In the absence of librations,the granular material forms a cylindrical layer near the outer boundary of the a...The dynamics of fluid and non-buoyant particles in a librating horizontal annulus is studied experimentally.In the absence of librations,the granular material forms a cylindrical layer near the outer boundary of the annulus and undergoes rigid-body rotation with the fluid and the annulus.It is demonstrated that the librational liquefaction of the granular material results in pattern formation.This self-organization process stems from the excitation of inertial modes induced by the oscillatory motion of liquefied granular material under the influence of the gravitational force.The inertial wave induces vortical fluid flow which entrains particles from rest and forms eroded areas that are equidistant from each other along the axis of rotation.Theoretical analysis and experiments demonstrate that a liquefied layer of granular material oscillates with a radian frequency equal to the angular velocity of the annulus and interacts with the inertial wave it excites.The new phenomenon of libration-induced pattern formation is of practical interest as it can be used to control multiphase flows and mass transfer in rotating containers in a variety of industrial processes.展开更多
This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramj...This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramjet-based RDE fueled by gaseous ethylene are performed in OpenFOAM for configurations with 15,30,45,and 60 orifices at a flight Mach number of 4.The results show that fuels with a stripped distribution are primarily mixed via tangential diffusion in the cold flow field.The configuration with more orifices has a better upstream mixing efficiency,whereas its downstream mixing efficiency,which is limited by the depth of penetration,is difficult to improve further.Backward Pressure Perturbations(BPPs)opposite to the propagation direction of Rotating Detonation Waves(RDWs)are produced by the reflection of the upstream oblique shock wave with the incoming stream and the hot release of local reactions after RDWs,which significantly affects the propagation mode and mixing.The RDWs propagate in the stable single-wave mode in configurations with 45 or 60 orifices and in the multi-wave mode in configurations with 30 orifices,whereas they fail in configurations with 15 orifices.Compared with that in the cold flow field,deceleration of the main flow,pressurization,and tangential velocity perturbation caused by the RDW substantially enhance the mixing efficiency.Moreover,the tangential velocity perturbations of upstream oblique shock waves and BPPs reduce the unevenness of the fuel distribution for the next cycle.This study reveals the mixing enhancement mechanism of RDWs and can contribute to the design of the injection scheme of the RDE.展开更多
Two-dimensional(2D)direct numerical simulations on the dynamics of three identical ferrofluid droplets suspended in a non-magnetic ambient fluid under a rotating uniform magnetic field are conducted,and the motion and...Two-dimensional(2D)direct numerical simulations on the dynamics of three identical ferrofluid droplets suspended in a non-magnetic ambient fluid under a rotating uniform magnetic field are conducted,and the motion and deformation of the three ferrofluid droplets are studied in this paper.Results show that there are four modes(i.e.,the three droplets'direct coalescence(TC),the coalescence of two droplets and the subsequent planetary motion with the third droplet(CAP),the three droplets'planetary motion(TP),and the independent spin(IS))for the three ferrofluid droplets,dependent on the magnetic Bond number(Bom)and the initial distance(d0)between two of the droplets.It is found that the decrease in d0and the increase in Bomcan make the droplets'mode change from the IS to the planetary motion,and then turn to the CAP.Furthermore,reducing Bomor d0is helpful for the droplets to become merged.展开更多
A high-quality welding method,named plasma arc welding apparatus with rotating tungsten electrode(abbreviated as PAW-RT),was proposed in this paper.The rotation speed could be adjusted from 0 to 15000 r/min.The rotary...A high-quality welding method,named plasma arc welding apparatus with rotating tungsten electrode(abbreviated as PAW-RT),was proposed in this paper.The rotation speed could be adjusted from 0 to 15000 r/min.The rotary motion of the tungsten needle trans-ferred circumferential momentum to the arc as well as the molten pool,thereby conferring the latter with rotating fluid flow charac-teristics.The influences of tungsten electrode rotation speed on PAW arc morphology,weld formation and interfacial microstructure of the final weld joints were discussed by the experimental procedures involving in-situ ablation,surfacing and butt welding.The ex-periments were conducted on Q235B steel.The results indicated that the increase of tungsten electrode rotation speed in PAW-RT contributed to improving arc eccentricity,leading to aesthetically improved welds with more uniformity.Additionally,the strength,hardness and toughness of the welded joint increased,while porosity was reduced.展开更多
In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stag...In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.展开更多
Aerodynamic drag is the dominant factor contributing to energy consumption as the operational speed of high speed trains increases,necessitating effective aerodynamic optimization strategies.This study investigates th...Aerodynamic drag is the dominant factor contributing to energy consumption as the operational speed of high speed trains increases,necessitating effective aerodynamic optimization strategies.This study investigates the aerodynamic characteristics of the bogie region under two bogie fairing configurations:baseline bogie fairing(BBF)and full bogie fairing(FBF).Both stationary and rotating wheelset conditions are considered.Wind tunnel experiments were conducted on a full-scale bogie model equipped with a wheelset drive system to simulate wheelset rotation.Additionally,numerical simulations were employed to analyze flow structures.Results indicate that the FBF configuration promotes a more uniform front-to-rear pressure distribution in the bogie region.The rotation of the wheelset notably affects the airflow near the wheels and extends its influence throughout the entire bogie region.Specifically,wheelset rotation reduces drag by 6.38%in the BBF configuration but increases drag by 3.5%in the FBF configuration.Further analysis reveals that,in the FBF configuration,aerodynamic drag primarily originates from the wheelsets.The rotating wheelset increases the aerodynamic drag by 18.8%for the rear wheelset,which is attributed to the shift in the pressure curve on the wheelset in the rotating direction.Therefore,the impact of wheelset rotation on aerodynamic characteristics should not be overlooked.展开更多
Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or hig...Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or high temperatures.These demanding working conditions considerably influence the dynamic performance of blades.Therefore,because of the challenges posed by blades in complex working environments,in-depth research and optimization are necessary to ensure that blades can operate safely and efficiently,thus guaranteeing the reliability and performance of mechanical systems.Focusing on the vibration analysis of blades in rotating machinery,this paper conducts a comprehensive literature review on the research advancements in vibration modeling and structural optimization of blades under complex operational conditions.First,the paper outlines the development of several modeling theories for rotating blades,including one-dimensional beam theory,two-dimensional plate-shell theory,and three-dimensional solid theory.Second,the research progress in the vibrational analysis of blades under aerodynamic loads,thermal environments,and crack factors is separately discussed.Finally,the developments in rotating blade structural optimization are presented from material optimization and shape optimization perspectives.The methodology and theory of analyzing and optimizing blade vibration characteristics under multifactorial operating conditions are comprehensively outlined,aiming to assist future researchers in proposing more effective and practical approaches for the vibration analysis and optimization of blades.展开更多
Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the...Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the“thermovibrational mechanism”.Convective flow is excited due to oscillations of a non-isothermal rotating fluid.Thermal vibrational convectionmanifests in the form of two-dimensional vortices elongated along the axis of rotation,which develop in a threshold manner with an increase in the amplitude of fluid oscillations.The objective of the present study is to clarify the nature of another phenomenon,i.e.,three-dimensional convective vortices observed in the experiments both before the excitation of the convection described above and in the supercritical region.The experimental study of the oscillatory and the time-averaged flow fields by particle image velocimetry is accompanied by the theoretical research of inertial waves.It is found that three-dimensional fluid flows owe their origin to inertial waves.This is confirmed by a high degree of agreement between the experimental and theoretical results.Experiments with cavities of different lengths indicate that the vortices are clearly seen in cavities thatmeet the conditions of resonant excitation of inertial modes.Furthermore,the length of the cavity has no effect on heat transfer,which is explained by the comparatively low intensity of the wave-induced flows.The main contribution to heat transfer is due to vortices elongated along the axis of rotation.The novel results are of significant practical importance in various fields.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.62471180)。
文摘We propose a novel cooling protocol within a triple-Laguerre-Gaussian cavity optomechanical system,which is designed to suppress the thermal vibrations of a rotating mirror to reach its quantum ground state.The system incorporates two auxiliary cavities and an atomic ensemble coupled to a Laguerre-Gaussian rotational cavity.By carefully selecting system parameters,the cooling process of the rotating mirror is significantly enhanced,while the heating process is effectively suppressed,enabling efficient ground-state cooling even in the unresolved sideband regime.Compared to previous works,our scheme reduces the stringent restrictions on auxiliary systems,making it more experimentally feasible under broader parameter conditions.These findings provide a robust approach for achieving ground-state cooling in mechanical resonators.
基金supported by the National Key Research and Development Program of China(2022YFA1404800)National Natural Science Foundation of China(12174107,12004221,12192254,92250304,W2441005,12334014,12192251)+4 种基金Natural Science Foundation of Shandong Province(ZR2024QA024,ZR2021ZD02)Postdoctoral Innovation Talents Support Program of Shandong Province(No.SDBX2019005)Shanghai Municipal Science and Technology Major ProjectFundamental Research Funds for the Central UniversitiesEngineering Research Center for Nanophotonics&Advanced Instrument,Ministry of Education,East China Normal University(No.2023nmc005)。
文摘We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating slit mechanism,a 3D symmetric spherical focal field distribution is created in the laser-irradiated regions of transparent substrates.The corresponding focal field distribution is theoretically calculated and validated by examining the features of laser-inscribed lines in glass samples.Moreover,we investigate the influences of laser writing speed and slit rotational speed on the fabrication resolution in glass,and discuss the formation mechanism of the generated periodic microstructures.To showcase its powerful capability for3D isotropic fabrication,the high-speed rotating slit beam shaping method is applied to create straight optical waveguides,bending optical waveguides,and hollow microchannels in the glass.The proposed method holds great potential for the facile manufacture of diverse 3D isotropic microstructures and devices within transparent materials across various applications,including advanced photonics,microoptics,micro-electromechanical systems,and microfluidics.
基金supported by the China National Postdoctoral Program for Innovative Talents(BX20230037)Talent Fund of Beijing Jiaotong University(2023XKRC034)+1 种基金China Postdoctoral Science Foundation(2023M730205)China Scholarship Council(202407090030)。
文摘As a type of emerging electro-mechanical conversion technology,triboelectric nanogenerators(TENGs)were widely applied in high-entropy energy harvesting,Internet of Things sensing,and biomedical fields due to the characteristics of lightweight,cheap,and high voltage.Among them,the rotating TENG has been extensively researched for its advantages,such as high-precision electrical signals,high electro-mechanical conversion efficiency,and effective output power.In this paper,the working mechanisms of four different rotating TENG modes were introduced in detail.Subsequently,a large amount of research works on the strengthening performance of rotating TENGs were comprehensively introduced and summarized by three gradient classifications.In addition,in view of the many applications of rotating TENGs,they were also systematically divided and generalized into three dimensions.Finally,the problems as well as challenges faced by the current rotating TENG research in the above 16 specific research directions were deeply analyzed,and the possible development directions and the solutions to the above problems were reasonably prospected in the next years.This review hopes to effectively promote the progress of rotating TENG on the road to commercialization.
基金supported in part by the National Natural Science Fundation of China under Grant Nos.62403263 and 62373207in part by the Natural Science Fundation of Qingdao,China under Grant No.24-4-4-zrjj-88-jch+1 种基金in part by the Team Plan for Youth Innovation of Universities in Shandong Province under Grant No.2024KJH148in part by the Foundation of Key Laboratory of Autonomous Systems and Networked Control(South China University of Technology),Ministry of Education under Grant No.2024A01.
文摘In this paper,we study the issue of controlling a rotating flexible body-beam system(RFBBS)which consists of a tip mass attached to the free-end and a rigid disk attached to the clamped-end of an Euler-Bernoulli beam.The boundary control input is affected by both unknown disturbance and nonlinear input backlash.First,the input backlash is considered as desired control input combined with a nonlinear input error,converting it to an external disturbance,and then,the control signal is designed through the energy-based control method.Next,the closed-loop system’s stability is analysed through Lyapunov direct method.Finally,the efficacy of the proposed control scheme is tested through numerical simulations utilizing the finite difference method.
基金partially supported by the National Natural Science Foundation of China(Nos.61901494,62101563)。
文摘Rotating Single-Baseline Interferometer(RSBI)systems have attracted considerable attention for Direct Position Determination(DPD)due to their simplicity and high localization accuracy.Nevertheless,the growing complexity of electromagnetic environments has led to scenarios with multiple time-frequency aliased sources,rendering conventional DPD methods for RSBI systems ineffective.Previous studies have predominantly concentrated on deploying antenna arrays and applying related signal-processing techniques for localization.Typically,these approaches necessitate that the number of physical antennas exceeds the number of sources.For RSBI systems already in practical operation,this would entail the installation of additional physical antennas,which implies equipment recycling and hardware upgrades.In numerous cases,such modifications are unfeasible.This paper proposes a novel Relative Offset-based Direct Position Determination(RO-DPD)method for RSBI systems that can handle multiple time-frequency aliased sources.The proposed method overcomes the challenge of simultaneous positioning without requiring hardware modifications by leveraging time accumulation and algorithmic enhancements.The implementation of the method involves three key steps.Firstly,the rotation of the interferometer is synthesized into a virtual Uniform Circular Array(UCA).Secondly,a novel estimation variable,termed relative offset,is introduced.The variable serves as an intermediate parameter to establish correlation equations between the positions of multiple time-frequency aliased sources and the intercepted signals.Thirdly,the relative offset model in the UCA is transformed into a virtual Uniform Linear Array(ULA)model,from which the cost function can be derived via the Spatial Smoothing(SS)MUSIC algorithm.Theoretical analysis and simulation results verify the effectiveness of the proposed method.Compared with traditional approaches,the RO-DPD method maintains the low complexity of RSBI systems while demonstrating robust performance in complex electromagnetic environments.
基金financially supported by the National Natural Science Foundation of China(Grant No.62431006)the Inner Mongolia Major Science and Technology Project(Grant No.2020ZD0024)+2 种基金Local Science and Technology Development Project of the Central Government(Grant Nos.2021ZY0006,2022ZY0011)Natural Science Foundation of Inner Mongolia(Grant No.2024LHMS05046)Inner Mongolia Autonomous Region Key Research and Technological Achievements Transformation Plan Project(Grant No.2023YFHH0063).
文摘Existing nanogenerator technologies for harvesting high-power energy from wind encounter significant chal-lenges due to limitations in current output.Here,we propose a rotating-switch triboelectric nanogenerator(RS-TENG)that uses mechanical triggering switches(on-off-on)to enhance the instantaneous current pulses during rotation.The rotating-switch in the proposed device addresses the issue of low instantaneous current output in triboelectric nanogenerators while maintaining voltage stability.At a constant rotational speed,the RS-TENG achieves an instantaneous current of 3.2 times that of its nonswitching counterpart,with an 89%reduction in response time.Furthermore,at a wind speed of 2 m·s^(-1),the RS-TENG achieves a wind power density of 10.4 mW·m^(-2)·m^(-1)·s.Additionally,by integrating the RS-TENG with energy management circuits,the nanogenerator can power wireless signal transmitters and temperature sensors,offering a self-sustaining power solution for remote wireless services.This research presents a promising technology for powering electronic devices in energy-scarce environments.
基金funded by the Ministry of Education of the Russian Federation within the framework of a state assignment,number 1023032300071-6-2.3.1.
文摘Thermal vibrational convection(TVC)refers to the time-averaged convection of a non-isothermal fluid subjected to oscillating force fields.It serves as an effective mechanism for heat transfer control,particularly under microgravity conditions.A key challenge in this field is understanding the effect of rotation on TVC,as fluid oscillations in rotating systems exhibit unique and specific characteristics.In this study,we examine TVC in a vertical flat layer with boundaries at different temperatures,rotating around a horizontal axis.The distinctive feature of this study is that the fluid oscillations within the cavity are not induced by vibrations of the cavity itself,but rather by the gravity field,giving them a tidal nature.Our findings reveal that inertial waves generated in the rotating layer qualitatively alter the TVC structure,producing time-averaged flows in the form of toroidal vortices.Experimental investigations of the structure of oscillatory and time-averaged flows,conducted using Particle Image Velocimetry(PIV)for flow velocity visualization,are complemented by theoretical calculations of inertial modes in a cavity with this geometry.To the best of our knowledge,this study represents the first of its kind.The agreement between experimental results and theoretical predictions confirms that the formation of convective structures in the form of toroidal vortices is driven by inertial waves induced by the gravity field.A decrease in the rotational velocity leads to a transformation of the convective structures,shifting from toroidal vortices of inertial-wave origin to classical cellular TVC.We present dimensionless parameters that define the excitation thresholds for both cellular convection and toroidal structures.
基金supported by the Shanghai Municipal Health Commission Funds(No.20214Y0026).
文摘The purpose of this study was to evaluate the clinical application of a rotating pod and assess its dosimetric considerations,positional accuracy,and anatomical structure stability.A pre-dosimetric study conducted on 11 patients revealed the potential for lung dose reduction using the rotational pod.Subsequently,seven patients underwent treatment with the rotational pod,and the target coverage and organs at risk doses were compared with those of conventional methods.The positional accuracy of the rotational pod,in collaboration with the imaging guidance system,was analyzed.The Dice similarity coefficient(DSC)was used to assess the settlement of tumors,trachea,and thoracic vertebrae after rotation for 20 min.In the pre-dosimetric study,there was no statistically significant difference in the volume of the internal gross tumor volume receiving≥99%of the prescription dose between the pod and conventional couch plans.However,compared to conventional couch plans,pod plans demonstrated a significant reduction in the average lung dose by 5-53%(p<0.01).Patient accrual,comprising seven cases,revealed reduced lung doses(9-26%)in four patients.For the other three patients,although there was no significant reduction in the lung dose,the use of the 90°beamline contributed to a decrease in the patient admission waiting time.The positional errors between the beams for lateral,longitudinal,vertical,ISO,pitch,and roll directions were 0.0 mm±5.3 mm,-1.2 mm±2.3 mm,-1.1 mm±2.7 mm,0.0°±0.6°,-0.1°±0.5°,and 0.0°±0.8°,respectively.The DSC for the target region and thoracic vertebrae between CT images captured before and after a 20-min rotation was higher than 0.85,whereas the DSC for the trachea was approximately 0.8.The preliminary clinical application of the rotational pod for lung tumors in fixed ion beamlines shows promise for achieving target coverage,reducing lung dose,and maintaining position accuracy.
基金supported by the National Natural Science Foundation of China (Grant No. 12202204)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220953)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Science and Technology Association's Young Talent Nurturing Program of Jiangsu Province (Grant No. JSTJ-2024-004)
文摘In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.
基金supported by The National Natural Science Foundation of China under Grant(5247512)National Key Lab of Aerospace Power System and Plasma Technology Foundation(APSPT202304002).
文摘Rotating machinery is critical to industrial systems,necessitating robust anomaly detection(AD)to ensure operational safety and prevent failures.However,in real-world scenarios,monitoring data is typically unlabeled and often consists of normal samples contaminated with a small proportion of unknown anomalies.To address this,this paper proposes a diffusion-based AD method,Anomaly Detection Denoising Diffusion Probabilistic Model(AD-DDPM)for robust AD.The method employs a U-attention-net to capture local and global features and introduces a filtered contrastive mechanism to mitigate the impact of contaminated training data.By leveraging the probabilistic nature of diffusion models,AD-DDPM effectively models normal data distributions,achieving superior AD even with polluted samples.Experimental validation on fault simulation datasets demonstrates the method’s exceptional performance,outperforming traditional machine learning and deep learning baselines.The proposed approach offers a promising solution for reliable health monitoring in industrial settings.
基金supported by the National Natural Science Foundation of China(Grant Nos.11902002 and 51705002)the Sichuan Provincial Natural Science Foundation(Grant No.2022NSFSC0275)the University Outstanding Youth Researcher Support Program of the Education Department of Anhui Province,and the Teaching Project of the Education Department of Anhui Province(Grant No.2022xxsfkc023).
文摘This study focuses on coupled vibrations of rotating thin-walled composite beams subjected to hygrothermal effects.In the existing literature,many studies have been conducted on coupled bending-torsional vibration and resonance in hygrothermal environments.Few studies considered the coupled flapwise-edgewise and resonances of composite thin-walled beams.Considering this,the flapwise-edgewise coupling effects and resonant characteristics of rotating thin-walled composite beams in a hygrothermal environment are studied.The Rayleigh–Ritz method is used to solve the equations of the beam.Results indicate that flapwise-edgewise coupling factors are essential for the vibration analysis of rectangular thin-walled beams.The ply angle and setting angle strongly affect the internal and external resonances.Large ply angles can significantly reduce the chances of primary internal and external resonances occurring when the permitted rotational speed is lower.
基金The Innovative Projects of Key Disciplines of Civil Engineering of Changsha University of Science and Technology,24ZDXK07,Andi Lai。
文摘Odd elasticity introduces active moduli to the antisymmetric components of the elastic tensor,which describe the asymmetric coupling between different deformation modes in a medium and quantify the work extracted during quasi-static strain cycles.The introduction of active moduli renders the elastic tensor non-Hermitian,breaking the Maxwell-Betti reciprocity and enabling the observation of phenomena that cannot occur in traditional passive media.Here,we develop an analytical dynamic model for odd elastic circular plates to investigate the effects of odd elasticity on motion in rotationally symmetric geometries.We report a novel nonreciprocal rotating wave and explore the effects of different odd elastic moduli on chiral deformation.Nonreciprocal rotating waves represent a distinct dynamic mode,exhibiting unidirectional propagation with amplitude increasing or decreasing exclusively along a specific direction.The amplitude change during motion reveals the system’s non-conservation of energy.
基金funded by the Ministry of Education of the Russian Federation within the framework of a state assignment,number 1023032300071-6-2.3.1.
文摘The dynamics of fluid and non-buoyant particles in a librating horizontal annulus is studied experimentally.In the absence of librations,the granular material forms a cylindrical layer near the outer boundary of the annulus and undergoes rigid-body rotation with the fluid and the annulus.It is demonstrated that the librational liquefaction of the granular material results in pattern formation.This self-organization process stems from the excitation of inertial modes induced by the oscillatory motion of liquefied granular material under the influence of the gravitational force.The inertial wave induces vortical fluid flow which entrains particles from rest and forms eroded areas that are equidistant from each other along the axis of rotation.Theoretical analysis and experiments demonstrate that a liquefied layer of granular material oscillates with a radian frequency equal to the angular velocity of the annulus and interacts with the inertial wave it excites.The new phenomenon of libration-induced pattern formation is of practical interest as it can be used to control multiphase flows and mass transfer in rotating containers in a variety of industrial processes.
基金supported from support from the National Natural Science Foundation of China(Nos.12441204,12302451 and 1202491)the Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20210075)。
文摘This study investigates the mixing enhancement mechanism and propagation characteristics of the detonation flow field of a Rotating Detonation Engine(RDE).Three-dimensional numerical simulations of a non-premixed ramjet-based RDE fueled by gaseous ethylene are performed in OpenFOAM for configurations with 15,30,45,and 60 orifices at a flight Mach number of 4.The results show that fuels with a stripped distribution are primarily mixed via tangential diffusion in the cold flow field.The configuration with more orifices has a better upstream mixing efficiency,whereas its downstream mixing efficiency,which is limited by the depth of penetration,is difficult to improve further.Backward Pressure Perturbations(BPPs)opposite to the propagation direction of Rotating Detonation Waves(RDWs)are produced by the reflection of the upstream oblique shock wave with the incoming stream and the hot release of local reactions after RDWs,which significantly affects the propagation mode and mixing.The RDWs propagate in the stable single-wave mode in configurations with 45 or 60 orifices and in the multi-wave mode in configurations with 30 orifices,whereas they fail in configurations with 15 orifices.Compared with that in the cold flow field,deceleration of the main flow,pressurization,and tangential velocity perturbation caused by the RDW substantially enhance the mixing efficiency.Moreover,the tangential velocity perturbations of upstream oblique shock waves and BPPs reduce the unevenness of the fuel distribution for the next cycle.This study reveals the mixing enhancement mechanism of RDWs and can contribute to the design of the injection scheme of the RDE.
基金Project supported by the National Natural Science Foundation of China(No.12372263)。
文摘Two-dimensional(2D)direct numerical simulations on the dynamics of three identical ferrofluid droplets suspended in a non-magnetic ambient fluid under a rotating uniform magnetic field are conducted,and the motion and deformation of the three ferrofluid droplets are studied in this paper.Results show that there are four modes(i.e.,the three droplets'direct coalescence(TC),the coalescence of two droplets and the subsequent planetary motion with the third droplet(CAP),the three droplets'planetary motion(TP),and the independent spin(IS))for the three ferrofluid droplets,dependent on the magnetic Bond number(Bom)and the initial distance(d0)between two of the droplets.It is found that the decrease in d0and the increase in Bomcan make the droplets'mode change from the IS to the planetary motion,and then turn to the CAP.Furthermore,reducing Bomor d0is helpful for the droplets to become merged.
基金supported by the National Natural Science Foundation of China(U22B20127)the National Natural Science Foundation of China(52175305)Taishan Scholars Project(tstp20230618).
文摘A high-quality welding method,named plasma arc welding apparatus with rotating tungsten electrode(abbreviated as PAW-RT),was proposed in this paper.The rotation speed could be adjusted from 0 to 15000 r/min.The rotary motion of the tungsten needle trans-ferred circumferential momentum to the arc as well as the molten pool,thereby conferring the latter with rotating fluid flow charac-teristics.The influences of tungsten electrode rotation speed on PAW arc morphology,weld formation and interfacial microstructure of the final weld joints were discussed by the experimental procedures involving in-situ ablation,surfacing and butt welding.The ex-periments were conducted on Q235B steel.The results indicated that the increase of tungsten electrode rotation speed in PAW-RT contributed to improving arc eccentricity,leading to aesthetically improved welds with more uniformity.Additionally,the strength,hardness and toughness of the welded joint increased,while porosity was reduced.
基金funded by the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement(Grant No.101026104)by the National Natural Science Foundation of China(Grant No.U20A6004)in part by the State Key Laboratory of Precision Electronics Manufacturing Technology and Equipment(Grant No.JMDZ202314).
文摘In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.
基金Projects(52322215,U2368213,U24B20119,12202142)supported by the National Natural Science Foundation of China。
文摘Aerodynamic drag is the dominant factor contributing to energy consumption as the operational speed of high speed trains increases,necessitating effective aerodynamic optimization strategies.This study investigates the aerodynamic characteristics of the bogie region under two bogie fairing configurations:baseline bogie fairing(BBF)and full bogie fairing(FBF).Both stationary and rotating wheelset conditions are considered.Wind tunnel experiments were conducted on a full-scale bogie model equipped with a wheelset drive system to simulate wheelset rotation.Additionally,numerical simulations were employed to analyze flow structures.Results indicate that the FBF configuration promotes a more uniform front-to-rear pressure distribution in the bogie region.The rotation of the wheelset notably affects the airflow near the wheels and extends its influence throughout the entire bogie region.Specifically,wheelset rotation reduces drag by 6.38%in the BBF configuration but increases drag by 3.5%in the FBF configuration.Further analysis reveals that,in the FBF configuration,aerodynamic drag primarily originates from the wheelsets.The rotating wheelset increases the aerodynamic drag by 18.8%for the rear wheelset,which is attributed to the shift in the pressure curve on the wheelset in the rotating direction.Therefore,the impact of wheelset rotation on aerodynamic characteristics should not be overlooked.
基金Supported by the National Natural Science Foundation of China under Grant No.52271309Natural Science Foundation of Heilongjiang Province of China under Grant No.YQ2022E104.
文摘Blades are important parts of rotating machinery such as marine gas turbines and wind turbines,which are exposed to harsh environments during mechanical operations,including centrifugal loads,aerodynamic forces,or high temperatures.These demanding working conditions considerably influence the dynamic performance of blades.Therefore,because of the challenges posed by blades in complex working environments,in-depth research and optimization are necessary to ensure that blades can operate safely and efficiently,thus guaranteeing the reliability and performance of mechanical systems.Focusing on the vibration analysis of blades in rotating machinery,this paper conducts a comprehensive literature review on the research advancements in vibration modeling and structural optimization of blades under complex operational conditions.First,the paper outlines the development of several modeling theories for rotating blades,including one-dimensional beam theory,two-dimensional plate-shell theory,and three-dimensional solid theory.Second,the research progress in the vibrational analysis of blades under aerodynamic loads,thermal environments,and crack factors is separately discussed.Finally,the developments in rotating blade structural optimization are presented from material optimization and shape optimization perspectives.The methodology and theory of analyzing and optimizing blade vibration characteristics under multifactorial operating conditions are comprehensively outlined,aiming to assist future researchers in proposing more effective and practical approaches for the vibration analysis and optimization of blades.
基金funded by the Ministry of Education of the Russian Federation within the framework of a state assignment,number 1023032300071-6-2.3.1.
文摘Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied.The centrifugal force plays a stabilizing role,while thermal convection is determined by the“thermovibrational mechanism”.Convective flow is excited due to oscillations of a non-isothermal rotating fluid.Thermal vibrational convectionmanifests in the form of two-dimensional vortices elongated along the axis of rotation,which develop in a threshold manner with an increase in the amplitude of fluid oscillations.The objective of the present study is to clarify the nature of another phenomenon,i.e.,three-dimensional convective vortices observed in the experiments both before the excitation of the convection described above and in the supercritical region.The experimental study of the oscillatory and the time-averaged flow fields by particle image velocimetry is accompanied by the theoretical research of inertial waves.It is found that three-dimensional fluid flows owe their origin to inertial waves.This is confirmed by a high degree of agreement between the experimental and theoretical results.Experiments with cavities of different lengths indicate that the vortices are clearly seen in cavities thatmeet the conditions of resonant excitation of inertial modes.Furthermore,the length of the cavity has no effect on heat transfer,which is explained by the comparatively low intensity of the wave-induced flows.The main contribution to heat transfer is due to vortices elongated along the axis of rotation.The novel results are of significant practical importance in various fields.
