Some municipal solid waste （MSW） can be used as the fuel. Combustion of MSW with high nitrogen content is successfully conducted in a lab-scale vortexing fluidized-bed incinerator （VFBI）. Pigskin with 16.5 wt.% ni...Some municipal solid waste （MSW） can be used as the fuel. Combustion of MSW with high nitrogen content is successfully conducted in a lab-scale vortexing fluidized-bed incinerator （VFBI）. Pigskin with 16.5 wt.% nitrogen content was used to simulate the high nitrogen content kitchen waste, and silica sand was used as the bed material. The effects of operating conditions, such as the bed temperature, freeboard temperature, excess oxygen ratio, and static bed height on the CO and NO concentrations at the exit of combustor and cyclone were investigated. The experimental results show that the freeboard temperature is the most important factor for CO emission. The order of operating conditions impact on the NO emission is： （1） excess oxygen ratio; （2） bed temperature; （3） freeboard temperature; and （4） static bed height. Utilizing cyclone can significantly reduce the CO emission concentration when the CO concentration released from the freeboard is higher than 50 ppm. On the other hand, the cyclone has no significant effect on the NO emission. Despite having high nitrogen content, a low conversion from fuel-N to NO was attained. Compared with other types of combustors, VFBI reduces the CO and NO emission concentrations much better when burning MSW with high nitrogen content.展开更多
Rice husk with high volatile content was burned in a pilot scale vortexing fluidized bed incinerator. The fluidized bed incinerator was constructed of 6 mm stainless steel with 0.45 m in diameter and 5 m in height. Th...Rice husk with high volatile content was burned in a pilot scale vortexing fluidized bed incinerator. The fluidized bed incinerator was constructed of 6 mm stainless steel with 0.45 m in diameter and 5 m in height. The emission characteristics of CO, NO, and SO2 were studied. The effects of operating parameters, such as primary air flow rate, secondary air flow rate, and excess air ratio on the pollutant emissions were also investigated. The results show that a large proportion of combustion occurs at the bed surface and the freeboard zone. The SO2 concentration in the flue gas decreases with increasing excess air ratio, while the NOx concentration shows reverse trend. The flow rate of secondary air has a significant impact on the CO emission. For a fixed primary air flowrate, CO emission decreases with the secondary air flowrate. For a fixed excess air ratio, CO emission decreases with the ratio of secondary to primary air flow. The minimum CO emission of 72 ppm is attained at the operating condition of 40% excess air ratio and 0.6 partition air ratio. The NOx and SO2 concentrations in the flue gas at this condition are 159 and 36 ppm, which conform to the EPA regulation of Taiwan.展开更多
Gas flows and particle mass flux were measured and clutriation experimentswere conducted in two cold test models of vortexing fluidized bed(VFB).The experimen-tal results show that the secondary air injected tangentia...Gas flows and particle mass flux were measured and clutriation experimentswere conducted in two cold test models of vortexing fluidized bed(VFB).The experimen-tal results show that the secondary air injected tangentially creates strong vortexes,estab-lishes particle suspension layers and internal circulation,and suppresses the elutriation offine particles greatly.The vortexing fluidized bed combustion has bright prospect bccauseof its much higher combustion efficiency and desulphidation efficiency than bubblingfluidized bed combustion due to long particle residence time and high slip velocity betweengas and solid,and its simpler configuration and lower cost than circulating fluidized bedcombustion.展开更多
BACKGROUND A previous study compared vortexing and Maki techniques for the diagnosis of catheter-related bloodstream infection(CRBSI),and concluded that vortexing was not superior to Maki method.AIM To determine wheth...BACKGROUND A previous study compared vortexing and Maki techniques for the diagnosis of catheter-related bloodstream infection(CRBSI),and concluded that vortexing was not superior to Maki method.AIM To determine whether the combined use of vortexing and Maki techniques provides profitability versus the Maki technique for the diagnosis of catheter tip colonization(CTC)and CRBSI.METHODS Observational and prospective study carried out in an Intensive Care Unit.Patients with suspected catheter-related infection(CRI)and with one central venous catheter for at least 7 days were included.The area under the curve(AUC)of the Maki technique,the vortexing technique and the combination of both techniques for the diagnosis of CTC and CRBSI were compared.RESULTS We included 136 episodes of suspected CRI.We found 21 cases of CTC of which 10 were also CRBSI cases.Of the 21 CTC episodes,18(85.7%)were diagnosed by Maki technique and vortexing technique,3(14.3%)only by the technique of Maki,and none only by technique of vortexing.Of the 10 CRBSI episodes,9(90.0%)were diagnosed by the techniques of Maki and vortexing,1(10.0%)was diagnosed only by the technique of Maki,and none only by the technique of vortexing.We no found differences in the comparison of AUC between the technique of Maki and the combination of Maki and vortexing techniques for the diagnosis of CTC(P=0.99)and CRBSI(P=0.99).CONCLUSION The novel finding of our study was that the combined use of vortexing and Maki techniques did not provide profitability to the technique of Maki alone to CRBSI diagnosis of.展开更多
This paper examines a model that combines vortex generators and leading-edge tubercles for controlling the laminar separation bubble(LSB)over an airfoil at low Reynolds numbers(Re).This new concept of passive flow con...This paper examines a model that combines vortex generators and leading-edge tubercles for controlling the laminar separation bubble(LSB)over an airfoil at low Reynolds numbers(Re).This new concept of passive flow control technique utilizing a tubercle and vortex generator(VG)close to the leading edge was analyzed numerically for a NACA0015 airfoil.In this study,the Shear Stress Transport(SST)turbulence model was employed in the numerical modelling.Numerical modelling was completed using the ANSYS-Fluent 18.2 solver.Analyses were conducted to investigate the flow pattern and understand the underlying LSB control phenomena that enabled the new passive flow control method to provide this significant performance benefit.The findings indicated that the new concept of passive flow control technique suppressed the formation of an LSB at the suction surface of the NACA0015 airfoil,resulting in a higher lift coefficient and improved aerodynamic performance.Improvements in LSB dynamics and aerodynamic performance through the passive flow control method lead to increased energy output and enhanced stability.展开更多
This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic li...This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.展开更多
The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study pro...The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.展开更多
Typhoon Bebinca in 2024 experienced a nearshore outbreak(a rapid intensification(RI)near the coast),making accurate forecasting of unpredictable tracks and intensities highly challenging.The AI model is superior to th...Typhoon Bebinca in 2024 experienced a nearshore outbreak(a rapid intensification(RI)near the coast),making accurate forecasting of unpredictable tracks and intensities highly challenging.The AI model is superior to the numerical model for typhoon track prediction but performs worse for intensity forecasting.Vortex initialization is an effective approach to further improve numerical prediction via cycle assimilation,accounting for multiple relocating TC centers and adjusting the typhoon initial structure.In addition,by integrating numerical runs with an AI weather model through real-time dynamic weight correction of the forecast,the predictive skill is further improved.For example,it can reduce the deviation of 72-h track forecasting by 25%compared with the numerical model and decrease the intensity deviation by 2%and 56%relative to the numerical run and AI forecasts,respectively.On the basis of the best-performing forecasting,the inner-core convective burst(CB)characteristics are illuminated.The attributions of the nearshore outbreak and RI of Typhoon Bebinca are examined.From the viewpoint of bottom-up convection growth,the CB is associated with the energy supply from the high-boundarylayer CAPE,the following upward-developing secondary circulation,and accompanying latent heat release of hydrometeors.The contracted radius of maximum winds(RMW)and increased inertial stability within the inner core region effectively prevent the escape of the high-energy atmosphere and favor rapid intensification and maintenance of the offshore burst of a typhoon.The intensifying secondary circulation further promotes the primary circulation of the TC and RI processes through the gradient wind balance.展开更多
With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation ...With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation in crystals driven by optical skyrmions.We find that although the skyrmion number is not conserved,the resulting high-order harmonics can exhibit a distinctive multi-vortex structure,whose features are shaped by both the topology of the optical skyrmions and the rotational symmetry of the crystal.The position of the vortex centers can be effectively tuned by employing different types of optical skyrmions.To elucidate the underlying physics,we develop a multi-absorption channel model based on the conservation laws of spin and orbital angular momentum.Our work explores the role of optical topology in extreme nonlinear light-matter interactions,offering new opportunities for the formation and manipulation of optical vortices and novel structured light fields in the visible and ultraviolet regimes.展开更多
This paper examines the connection between photonic band-gap formation in two types of two-dimensional photonic crystals and the emergence of reverse electromagnetic energy flows generated by linearly polarized plane ...This paper examines the connection between photonic band-gap formation in two types of two-dimensional photonic crystals and the emergence of reverse electromagnetic energy flows generated by linearly polarized plane waves incident on a photonic-crystal slab.We show that these reverse energy flows,observed in both transmitted and reflected fields,originate from vortex structures in the Poynting vector.The resulting energy-flow patterns exhibit striking analogies to vortex formation in fluid motion past obstacles.The geometry and dynamics of the Poynting-vector vortices determine whether the incident electromagnetic energy is impeded,leading to the formation of photonic band gaps,or instead guided through the structure,enabling transmission.展开更多
The Northeast China Cold Vortex(NCCV)is a common cut-off low-pressure system in Northeast China,frequently causing localized heavy rainfall,strong winds,and thunderstorms during the early summer.In this study,the clea...The Northeast China Cold Vortex(NCCV)is a common cut-off low-pressure system in Northeast China,frequently causing localized heavy rainfall,strong winds,and thunderstorms during the early summer.In this study,the clear-sky radiance of 48 longwave channels from the FY-4B Geostationary Interferometric Infrared Sounder(GIIRS)is assimilated into the China Meteorological Administration mesoscale model(CMA-MESO)to evaluate its impact on NCCV development and its effects on rainfall forecasting.The results show that after assimilating the GIIRS radiance data,the warm center at 200 hPa and the cold center at 850 hPa of the NCCV are strengthened,and the dry intrusion at 850 hPa becomes more pronounced.This leads to a stronger NCCV intensity in the following 24 hours and brings the precipitation intensity and area closer to the observation,resulting in significant improvements compared to the experiments that do not assimilate GIIRS radiance data.Furthermore,it is found that the enhancement of the precipitation forecast is associated with the strengthening of cold air in the middle and lower troposphere,which intensifies the uplift of the warm,moist airflow.These results highlight the potential value of GIIRS data assimilation in enhancing early warnings and forecasts of extreme weather events influenced by the NCCV.展开更多
We study Onsager vortex clustered states in a shell-shaped superfluid containing a large number of quantum vortices.In the incompressible limit and at low temperatures,the relevant problem can be boiled down to the st...We study Onsager vortex clustered states in a shell-shaped superfluid containing a large number of quantum vortices.In the incompressible limit and at low temperatures,the relevant problem can be boiled down to the statistical mechanics of neutral point vortices confined on a sphere.We analyze rotation-free vortex-clustered states within the mean-field theory in the microcanonical ensemble.We find that the sandwich state,which involves the separating of vortices with opposite circulation and the clustering of vortices with the same circulation around the poles and the equator,is the maximum entropy vortex distribution,subject to a zero angular momentum constraint.The dipole moment vanishes for the sandwich state and the quadrupole tensor serves as an order parameter to characterize the vortex cluster structure.For a given finite angular momentum,the equilibrium vortex distribution forms a dipole structure,i.e.,vortices with opposite sign are separated and accumulate around the south and north poles,respectively.The conditions for the onset of clustering and the exponents associated with the quadrupole moment and the dipole moment as functions of energy are obtained within the mean field theory.At large energies,we obtain asymptotically exact vortex density distributions using the stereographic projection method,yielding the parameter bounds for the vortex clustered states.The analytical predictions are in excellent agreement with microcanonical Monte Carlo simulations.展开更多
The intrinsic interaction mechanism of flutter between the flow and structure of a rectangular plate remains a mystery from the viewpoint of unsteady flow.The present study provides a novel insight into this interacti...The intrinsic interaction mechanism of flutter between the flow and structure of a rectangular plate remains a mystery from the viewpoint of unsteady flow.The present study provides a novel insight into this interaction mechanism based on an adequate understanding of the formation and evolution of the flapping leading-edge vortex(LEV).A series of wind tunnel tests was conducted to investigate the nonlinear flutter instability of an 8∶1 rectangular plate.The complete flow fields around the model throughout the flutter process were obtained by a particle image velocimetry(PIV)technique using two synchronous cameras with an interpolation and resampling method.To acquire the flow structures corresponding to the characteristic frequency of flutter,the spectral proper orthogonal decomposition(SPOD)method was extended to a noninertial frame to reconstruct the low-rank flow field during flutter and extract the characteristic flow pattern coupled with oscillations.It was found that when the 8∶1 rectangular plate undergoes flutter,the LEVs exhibit a periodic flapping phenomenon induced by the structure oscillations.A two-dimensional correlation analysis of the flapping LEVs was conducted for different inflow velocities.The results demonstrate that there is a substantial phase lead phenomenon in the LEV evolution downstream for a higher inflow velocity.This phenomenon may be related to a phase offset of aerodynamic forces,and finally,it gives rise to flutter.展开更多
Focusing on the unclear mechanism of aerodynamic interference in overlapping rotors of heavy-load electric vertical take-off and landing(eVTOL)aircraft,this paper aims to reveal the aerodynamic interference characteri...Focusing on the unclear mechanism of aerodynamic interference in overlapping rotors of heavy-load electric vertical take-off and landing(eVTOL)aircraft,this paper aims to reveal the aerodynamic interference characteristics and flow field evolution laws of overlapping rotor configurations in hovering conditions through numerical simulation methods.The research method involves constructing a computational model for rotor flow fields and aerodynamic characteristics based on the Reynolds-averaged Navier-Stokes(RANS)equations and the Spalart-Allmaras(S-A)turbulence model.The dynamic simulation of rotor rotational motion was achieved by using the moving nested grid technology.The reliability of the computational method was ensured through the grid independence verification and the comparison with experimental data.The research results indicate that in overlapping rotor systems,rotorⅡexperiences a decrease in thrust,significant power fluctuations,and reduced hovering efficiency due to continuous interference from the adjacent rotor’s wake and blade-vortex interactions.Blade-tip vortices undergo breakage,fusion,and secondary rolling in the overlapping region,forming large-scale turbulent structures that lead to attenuation of the induced velocity field and aerodynamic efficiency losses.Additionally,the interaction between the rotor downwash and the fuselage triggers a“fountain effect”and a sudden increase in surface pressure on the fuselage,exacerbating flow field distortion.Based on the aforementioned mechanisms,the safe flight of overlapping rotor configurations can be achieved by optimizing the configuration strategy of the rotational speed phase difference between adjacent blades.This study provides a theoretical basis for the rotor layout design and the aerodynamic performance enhancement of heavy-load eVTOL aircraft.展开更多
By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integra...By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.展开更多
This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,t...This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.展开更多
The free-surface vortex is a rotational flow phenomenon characterized by two-phase coupling,formed by the rupture of surface fluid in the final stage of discharge.It is a significant concept with broad applications in...The free-surface vortex is a rotational flow phenomenon characterized by two-phase coupling,formed by the rupture of surface fluid in the final stage of discharge.It is a significant concept with broad applications in engineering fields like metallurgy and hydraulics.The basic concepts and characteristics of free-surface vortices were introduced,and their hazards in various fields were discussed.The development of theoretical and numerical models over recent decades was reviewed,and the factors affecting vortex formation and existing suppression methods were outlined.Finally,the key challenges and focus areas on the study of free-surface vortex were summarized.With the ongoing advancements in computational fluid dynamics and experimental technology,research on free-surface vortices will become more in depth and precise.Additionally,interdisciplinary cooperation and technological innovation are expected to achieve precise control and optimal design of free-surface vortices,offering more efficient and sustainable solutions for metallurgy and related engineering fields.展开更多
The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to...The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.展开更多
We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW...We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW structure interacts with a weak probe laser field,a spatially independent 2D standing-wave(SW)field,and a Laguerre–Gaussian(LG)vortex field,respectively.The results indicate that the diffraction patterns are highly sensitive to amplitude modulation and phase modulation.Because of the existence of vortex light,it is possible to realize asymmetric high-order diffraction in the SQW structure,and then a 2D asymmetric grating is established.By adjusting the detunings of the probe field,vortex field,and SW field,as well as the interaction length,diffraction intensity,and direction of the 2D asymmetric electromagnetically induced grating(EIG)can be controlled effectively.In addition,the number of orbital angular momenta(OAM)and beam waist parameter can be used to modulate the diffraction intensity and energy transfer of the probe light in different regions.High-order diffraction intensity is enhanced and high-efficiency 2D asymmetric diffraction grating with different diffraction patterns is obtained in the scheme.Such 2D asymmetric diffraction grating may be beneficial to the research of optical communication and innovative semiconductor quantum devices.展开更多
Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and...Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and water.Nevertheless,a critical hurdle for these vehicles lies in mitigating the adverse effects of repeatedly transitioning between these environments,particularly during water-surface takeoffs.Currently,research on the interference caused by rotors approaching water surfaces remains limited.This paper introduces a novel adaptive rotor aerodynamic model based on continuous finite vortex theory to predict rotor thrust within gas–liquid flow field.Initially,the model's sensitivity to system parameters was analyzed to optimize its predictive capabilities.Subsequently,a comprehensive ground/water experimental setup was designed to investigate the intricate aerodynamic interactions between the rotor flow field and water.By varying rotor sizes,the characteristics of the rotor flow field and water surface were examined at different rotor-water surface distances.The performance of different modeling methods was analyzed based on the rotor experimental data of a diameter of 0.38 m,and the prediction results were quantified using the percentage of the mean-square error.The results show that the average error of the finite vortex rotor model is the smallest.Finally,a novel transition boundary is proposed to divide the rotor flow field of the gas–liquid mixture into two stages.The thrust loss zone is defined to delineate the safe operating range of the aircraft,providing a basis for the design of aerial-aquatic rotorcraft.展开更多
基金sponsored by the National Natural Science Foundation of China (No. 99-2221-E-003-057)
文摘Some municipal solid waste （MSW） can be used as the fuel. Combustion of MSW with high nitrogen content is successfully conducted in a lab-scale vortexing fluidized-bed incinerator （VFBI）. Pigskin with 16.5 wt.% nitrogen content was used to simulate the high nitrogen content kitchen waste, and silica sand was used as the bed material. The effects of operating conditions, such as the bed temperature, freeboard temperature, excess oxygen ratio, and static bed height on the CO and NO concentrations at the exit of combustor and cyclone were investigated. The experimental results show that the freeboard temperature is the most important factor for CO emission. The order of operating conditions impact on the NO emission is： （1） excess oxygen ratio; （2） bed temperature; （3） freeboard temperature; and （4） static bed height. Utilizing cyclone can significantly reduce the CO emission concentration when the CO concentration released from the freeboard is higher than 50 ppm. On the other hand, the cyclone has no significant effect on the NO emission. Despite having high nitrogen content, a low conversion from fuel-N to NO was attained. Compared with other types of combustors, VFBI reduces the CO and NO emission concentrations much better when burning MSW with high nitrogen content.
文摘Rice husk with high volatile content was burned in a pilot scale vortexing fluidized bed incinerator. The fluidized bed incinerator was constructed of 6 mm stainless steel with 0.45 m in diameter and 5 m in height. The emission characteristics of CO, NO, and SO2 were studied. The effects of operating parameters, such as primary air flow rate, secondary air flow rate, and excess air ratio on the pollutant emissions were also investigated. The results show that a large proportion of combustion occurs at the bed surface and the freeboard zone. The SO2 concentration in the flue gas decreases with increasing excess air ratio, while the NOx concentration shows reverse trend. The flow rate of secondary air has a significant impact on the CO emission. For a fixed primary air flowrate, CO emission decreases with the secondary air flowrate. For a fixed excess air ratio, CO emission decreases with the ratio of secondary to primary air flow. The minimum CO emission of 72 ppm is attained at the operating condition of 40% excess air ratio and 0.6 partition air ratio. The NOx and SO2 concentrations in the flue gas at this condition are 159 and 36 ppm, which conform to the EPA regulation of Taiwan.
文摘Gas flows and particle mass flux were measured and clutriation experimentswere conducted in two cold test models of vortexing fluidized bed(VFB).The experimen-tal results show that the secondary air injected tangentially creates strong vortexes,estab-lishes particle suspension layers and internal circulation,and suppresses the elutriation offine particles greatly.The vortexing fluidized bed combustion has bright prospect bccauseof its much higher combustion efficiency and desulphidation efficiency than bubblingfluidized bed combustion due to long particle residence time and high slip velocity betweengas and solid,and its simpler configuration and lower cost than circulating fluidized bedcombustion.
文摘BACKGROUND A previous study compared vortexing and Maki techniques for the diagnosis of catheter-related bloodstream infection(CRBSI),and concluded that vortexing was not superior to Maki method.AIM To determine whether the combined use of vortexing and Maki techniques provides profitability versus the Maki technique for the diagnosis of catheter tip colonization(CTC)and CRBSI.METHODS Observational and prospective study carried out in an Intensive Care Unit.Patients with suspected catheter-related infection(CRI)and with one central venous catheter for at least 7 days were included.The area under the curve(AUC)of the Maki technique,the vortexing technique and the combination of both techniques for the diagnosis of CTC and CRBSI were compared.RESULTS We included 136 episodes of suspected CRI.We found 21 cases of CTC of which 10 were also CRBSI cases.Of the 21 CTC episodes,18(85.7%)were diagnosed by Maki technique and vortexing technique,3(14.3%)only by the technique of Maki,and none only by technique of vortexing.Of the 10 CRBSI episodes,9(90.0%)were diagnosed by the techniques of Maki and vortexing,1(10.0%)was diagnosed only by the technique of Maki,and none only by the technique of vortexing.We no found differences in the comparison of AUC between the technique of Maki and the combination of Maki and vortexing techniques for the diagnosis of CTC(P=0.99)and CRBSI(P=0.99).CONCLUSION The novel finding of our study was that the combined use of vortexing and Maki techniques did not provide profitability to the technique of Maki alone to CRBSI diagnosis of.
基金the Scientific Research Projects Unit of Erciyes University under contract no:FDS-2022-11532 and FOA-2025-14773.
文摘This paper examines a model that combines vortex generators and leading-edge tubercles for controlling the laminar separation bubble(LSB)over an airfoil at low Reynolds numbers(Re).This new concept of passive flow control technique utilizing a tubercle and vortex generator(VG)close to the leading edge was analyzed numerically for a NACA0015 airfoil.In this study,the Shear Stress Transport(SST)turbulence model was employed in the numerical modelling.Numerical modelling was completed using the ANSYS-Fluent 18.2 solver.Analyses were conducted to investigate the flow pattern and understand the underlying LSB control phenomena that enabled the new passive flow control method to provide this significant performance benefit.The findings indicated that the new concept of passive flow control technique suppressed the formation of an LSB at the suction surface of the NACA0015 airfoil,resulting in a higher lift coefficient and improved aerodynamic performance.Improvements in LSB dynamics and aerodynamic performance through the passive flow control method lead to increased energy output and enhanced stability.
基金supported by the National Natural Science Foundation of China(Grant No.42305013)Joint Research Project for Meteorological Capacity Improvement(Grant Nos.23NLTSQ002 and 24NLTSQ001)+2 种基金China Meteorological Administration Tornado Key Laboratory(Grant No.TKL202307)the China Meteorological Administration Youth Innovation Team Fund(Grant No.CMA2024QN05)a research project of the Chinese Academy of Meteorological Science(Grant No.2023Z019)。
文摘This study presents a comprehensive analysis of 132 tornadic events in northeastern China from 2004 to 2023,utilizing radar and ERA5 reanalysis data to investigate the climatology,environmental drivers,and synoptic linkages with Northeast China cold vortices(NCCVs)of tornadic storms under different convective modes.Results reveal that discrete storms account for 70%of events,with clustered cells(CC)being the most frequent mode,while significant tornadoes(EF2+)are primarily associated with isolated cells(IC)and broken lines(BL).The storm mode distribution in northeastern China resembles that of the central United States but with a higher proportion of CC and lower IC.In contrast,southern China exhibits a higher frequency of quasi-linear(QL)modes(>50%),similar to European patterns.Although no single parameter clearly differentiates between all tornado modes,distinct morphological characteristics emerge through specific parameter combinations:NL modes are characterized by high 0-1 km storm-relative helicity(SRH1)and humidity but low 0-6 km shear(SR6),whereas IC modes display contrasting features with low SRH1 and high CAPE.Notably,83%of tornadoes are associated with NCCVs,preferentially forming in southeastern/southwestern quadrants.Strong tornadoes favor southeastern quadrants,while NCCV intensity correlates with tornadic distance from vortex centers.Three characteristic synoptic configurations emerge:(T1)strong deep vortices with vertically aligned cold troughs,generating southeast-dominant tornado clusters characterized by a high proportion of BL and QL modes;(T2)weaker vortices featuring sub-synoptic troughs,with southern-distributed events dominated by a predominance of the CC mode;(T3)transverse-trough systems exhibiting CAPE-SRH decoupling and reduced tornadic activity.This study enhances our understanding of tornadoes in northeastern China,informing future research on formation mechanisms,prediction methods,and disaster prevention strategies.
基金supported by the National Natural Science Foundation of China(Grant Nos.42192551,42150710531).
文摘The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB0760300)the National Natural Science Foundation of China (Grant Nos.42175010 and 41875079)。
文摘Typhoon Bebinca in 2024 experienced a nearshore outbreak(a rapid intensification(RI)near the coast),making accurate forecasting of unpredictable tracks and intensities highly challenging.The AI model is superior to the numerical model for typhoon track prediction but performs worse for intensity forecasting.Vortex initialization is an effective approach to further improve numerical prediction via cycle assimilation,accounting for multiple relocating TC centers and adjusting the typhoon initial structure.In addition,by integrating numerical runs with an AI weather model through real-time dynamic weight correction of the forecast,the predictive skill is further improved.For example,it can reduce the deviation of 72-h track forecasting by 25%compared with the numerical model and decrease the intensity deviation by 2%and 56%relative to the numerical run and AI forecasts,respectively.On the basis of the best-performing forecasting,the inner-core convective burst(CB)characteristics are illuminated.The attributions of the nearshore outbreak and RI of Typhoon Bebinca are examined.From the viewpoint of bottom-up convection growth,the CB is associated with the energy supply from the high-boundarylayer CAPE,the following upward-developing secondary circulation,and accompanying latent heat release of hydrometeors.The contracted radius of maximum winds(RMW)and increased inertial stability within the inner core region effectively prevent the escape of the high-energy atmosphere and favor rapid intensification and maintenance of the offshore burst of a typhoon.The intensifying secondary circulation further promotes the primary circulation of the TC and RI processes through the gradient wind balance.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12234002, 92250303, 12474486, 12504301, and 12504396)the National Key Research and Development Program of China (Grant No. 2024YFA1612101)。
文摘With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation in crystals driven by optical skyrmions.We find that although the skyrmion number is not conserved,the resulting high-order harmonics can exhibit a distinctive multi-vortex structure,whose features are shaped by both the topology of the optical skyrmions and the rotational symmetry of the crystal.The position of the vortex centers can be effectively tuned by employing different types of optical skyrmions.To elucidate the underlying physics,we develop a multi-absorption channel model based on the conservation laws of spin and orbital angular momentum.Our work explores the role of optical topology in extreme nonlinear light-matter interactions,offering new opportunities for the formation and manipulation of optical vortices and novel structured light fields in the visible and ultraviolet regimes.
文摘This paper examines the connection between photonic band-gap formation in two types of two-dimensional photonic crystals and the emergence of reverse electromagnetic energy flows generated by linearly polarized plane waves incident on a photonic-crystal slab.We show that these reverse energy flows,observed in both transmitted and reflected fields,originate from vortex structures in the Poynting vector.The resulting energy-flow patterns exhibit striking analogies to vortex formation in fluid motion past obstacles.The geometry and dynamics of the Poynting-vector vortices determine whether the incident electromagnetic energy is impeded,leading to the formation of photonic band gaps,or instead guided through the structure,enabling transmission.
基金sponsored by the National Natural Science Foundation of China(Grant No.42275171)the Basic Research Operating Expenses of the Institute of Meteorological Sciences,CMA(Grant No.2023Z019)+3 种基金the National Key Research and Development Program of China(Grant No.2022YFF0801304)the China Meteorological Administration Youth Innovation Team Fund(Grant No.CMA2024QN05)a Liaoning Provincial Meteorological Bureau Project(Grant No.D202201)Shenyang Institute of Atmospheric Environment Projects(Grant Nos.2022SYIAEJY13 and 2018SYIAEZD5).
文摘The Northeast China Cold Vortex(NCCV)is a common cut-off low-pressure system in Northeast China,frequently causing localized heavy rainfall,strong winds,and thunderstorms during the early summer.In this study,the clear-sky radiance of 48 longwave channels from the FY-4B Geostationary Interferometric Infrared Sounder(GIIRS)is assimilated into the China Meteorological Administration mesoscale model(CMA-MESO)to evaluate its impact on NCCV development and its effects on rainfall forecasting.The results show that after assimilating the GIIRS radiance data,the warm center at 200 hPa and the cold center at 850 hPa of the NCCV are strengthened,and the dry intrusion at 850 hPa becomes more pronounced.This leads to a stronger NCCV intensity in the following 24 hours and brings the precipitation intensity and area closer to the observation,resulting in significant improvements compared to the experiments that do not assimilate GIIRS radiance data.Furthermore,it is found that the enhancement of the precipitation forecast is associated with the strengthening of cold air in the middle and lower troposphere,which intensifies the uplift of the warm,moist airflow.These results highlight the potential value of GIIRS data assimilation in enhancing early warnings and forecasts of extreme weather events influenced by the NCCV.
基金support from the National Natural Science Foundation of China(Grant No.12175215,Grant No.12475041)the National Key Research and Development Program of China(Grant No.2022YFA 1405300)NSAF(Grant No.U2330401)。
文摘We study Onsager vortex clustered states in a shell-shaped superfluid containing a large number of quantum vortices.In the incompressible limit and at low temperatures,the relevant problem can be boiled down to the statistical mechanics of neutral point vortices confined on a sphere.We analyze rotation-free vortex-clustered states within the mean-field theory in the microcanonical ensemble.We find that the sandwich state,which involves the separating of vortices with opposite circulation and the clustering of vortices with the same circulation around the poles and the equator,is the maximum entropy vortex distribution,subject to a zero angular momentum constraint.The dipole moment vanishes for the sandwich state and the quadrupole tensor serves as an order parameter to characterize the vortex cluster structure.For a given finite angular momentum,the equilibrium vortex distribution forms a dipole structure,i.e.,vortices with opposite sign are separated and accumulate around the south and north poles,respectively.The conditions for the onset of clustering and the exponents associated with the quadrupole moment and the dipole moment as functions of energy are obtained within the mean field theory.At large energies,we obtain asymptotically exact vortex density distributions using the stereographic projection method,yielding the parameter bounds for the vortex clustered states.The analytical predictions are in excellent agreement with microcanonical Monte Carlo simulations.
基金The National Natural Science Foundation of China(No.52178470)the National Key Research and Development Program of China(No.2022YFC3005303).
文摘The intrinsic interaction mechanism of flutter between the flow and structure of a rectangular plate remains a mystery from the viewpoint of unsteady flow.The present study provides a novel insight into this interaction mechanism based on an adequate understanding of the formation and evolution of the flapping leading-edge vortex(LEV).A series of wind tunnel tests was conducted to investigate the nonlinear flutter instability of an 8∶1 rectangular plate.The complete flow fields around the model throughout the flutter process were obtained by a particle image velocimetry(PIV)technique using two synchronous cameras with an interpolation and resampling method.To acquire the flow structures corresponding to the characteristic frequency of flutter,the spectral proper orthogonal decomposition(SPOD)method was extended to a noninertial frame to reconstruct the low-rank flow field during flutter and extract the characteristic flow pattern coupled with oscillations.It was found that when the 8∶1 rectangular plate undergoes flutter,the LEVs exhibit a periodic flapping phenomenon induced by the structure oscillations.A two-dimensional correlation analysis of the flapping LEVs was conducted for different inflow velocities.The results demonstrate that there is a substantial phase lead phenomenon in the LEV evolution downstream for a higher inflow velocity.This phenomenon may be related to a phase offset of aerodynamic forces,and finally,it gives rise to flutter.
基金supported by the National Natural Science Foundation of China(No.11872211)。
文摘Focusing on the unclear mechanism of aerodynamic interference in overlapping rotors of heavy-load electric vertical take-off and landing(eVTOL)aircraft,this paper aims to reveal the aerodynamic interference characteristics and flow field evolution laws of overlapping rotor configurations in hovering conditions through numerical simulation methods.The research method involves constructing a computational model for rotor flow fields and aerodynamic characteristics based on the Reynolds-averaged Navier-Stokes(RANS)equations and the Spalart-Allmaras(S-A)turbulence model.The dynamic simulation of rotor rotational motion was achieved by using the moving nested grid technology.The reliability of the computational method was ensured through the grid independence verification and the comparison with experimental data.The research results indicate that in overlapping rotor systems,rotorⅡexperiences a decrease in thrust,significant power fluctuations,and reduced hovering efficiency due to continuous interference from the adjacent rotor’s wake and blade-vortex interactions.Blade-tip vortices undergo breakage,fusion,and secondary rolling in the overlapping region,forming large-scale turbulent structures that lead to attenuation of the induced velocity field and aerodynamic efficiency losses.Additionally,the interaction between the rotor downwash and the fuselage triggers a“fountain effect”and a sudden increase in surface pressure on the fuselage,exacerbating flow field distortion.Based on the aforementioned mechanisms,the safe flight of overlapping rotor configurations can be achieved by optimizing the configuration strategy of the rotational speed phase difference between adjacent blades.This study provides a theoretical basis for the rotor layout design and the aerodynamic performance enhancement of heavy-load eVTOL aircraft.
文摘By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.
基金supported by the National Key R&D Program of China(2022YFC3003903)Natural Science Foundation of Beijing(Grant No.8222079)and of China(Grant No.42475014,U2442204)the Basic Research Fund of CAMS(2023Z001).
文摘This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.
基金supported by the National Natural Science Foundation of China(Grant No.52474339)Anhui Province Outstanding Research and Innovation Team in Higher Education Institutions(Grant No.2022AH010024).
文摘The free-surface vortex is a rotational flow phenomenon characterized by two-phase coupling,formed by the rupture of surface fluid in the final stage of discharge.It is a significant concept with broad applications in engineering fields like metallurgy and hydraulics.The basic concepts and characteristics of free-surface vortices were introduced,and their hazards in various fields were discussed.The development of theoretical and numerical models over recent decades was reviewed,and the factors affecting vortex formation and existing suppression methods were outlined.Finally,the key challenges and focus areas on the study of free-surface vortex were summarized.With the ongoing advancements in computational fluid dynamics and experimental technology,research on free-surface vortices will become more in depth and precise.Additionally,interdisciplinary cooperation and technological innovation are expected to achieve precise control and optimal design of free-surface vortices,offering more efficient and sustainable solutions for metallurgy and related engineering fields.
基金Project(2020YFA0710903)supported by the National Key Research and Development Program of ChinaProject(2025ZZTS0623)supported by the Graduate Student Independent Innovation Project of Central South University,ChinaProject(202406370145)supported by the China Scholarship Council。
文摘The stability of high-speed trains under crosswind conditions has become a key consideration in aerodynamic design.As running speeds continue to increase and car body weight decreases,crosswinds pose a greater risk to train safety,significantly lowering the critical wind velocity.Therefore,developing strategies to enhance crosswind stability is essential.This study focuses on the leeward region adjacent to the train body,where separated flows with large vortices generate significant negative surface pressure.Enhancing this negative pressure distribution is proposed as a potential method to improve a train’s resistance to overturning.To achieve this,winglets are installed on the leeward side as a flow control measure,and their effects at different deflection angles are evaluated.The influence of five deflection angles on the leeward-side flow field and aerodynamic loads is analyzed,considering the head,middle,and tail cars.Results indicate that a deflection angle of 90°optimally reduces the overall overturning moment by 27.6%compared to the baseline model in a three-car configuration.These findings highlight that optimizing the winglet deflection angle to approximately 90°can significantly enhance a train’s resistance to overturning,offering valuable insights for aerodynamic optimization in strong wind conditions.
基金supported by the National Natural Science Foundation of China(Grant No.12105210)the Knowledge Innovation Program of Wuhan-Basi Research(Grant No.2023010201010149)。
文摘We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW structure interacts with a weak probe laser field,a spatially independent 2D standing-wave(SW)field,and a Laguerre–Gaussian(LG)vortex field,respectively.The results indicate that the diffraction patterns are highly sensitive to amplitude modulation and phase modulation.Because of the existence of vortex light,it is possible to realize asymmetric high-order diffraction in the SQW structure,and then a 2D asymmetric grating is established.By adjusting the detunings of the probe field,vortex field,and SW field,as well as the interaction length,diffraction intensity,and direction of the 2D asymmetric electromagnetically induced grating(EIG)can be controlled effectively.In addition,the number of orbital angular momenta(OAM)and beam waist parameter can be used to modulate the diffraction intensity and energy transfer of the probe light in different regions.High-order diffraction intensity is enhanced and high-efficiency 2D asymmetric diffraction grating with different diffraction patterns is obtained in the scheme.Such 2D asymmetric diffraction grating may be beneficial to the research of optical communication and innovative semiconductor quantum devices.
基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0532)the Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(Nos.2024-KF03001,2024-KF03003)the National Natural Science Foundation of China(No.12272169)for the financial support。
文摘Blending the agility of aerial drones with the covert capabilities of underwater submersibles,the aerial-aquatic rotorcraft has garnered substantial interest due to their unparalleled capacity to traverse both air and water.Nevertheless,a critical hurdle for these vehicles lies in mitigating the adverse effects of repeatedly transitioning between these environments,particularly during water-surface takeoffs.Currently,research on the interference caused by rotors approaching water surfaces remains limited.This paper introduces a novel adaptive rotor aerodynamic model based on continuous finite vortex theory to predict rotor thrust within gas–liquid flow field.Initially,the model's sensitivity to system parameters was analyzed to optimize its predictive capabilities.Subsequently,a comprehensive ground/water experimental setup was designed to investigate the intricate aerodynamic interactions between the rotor flow field and water.By varying rotor sizes,the characteristics of the rotor flow field and water surface were examined at different rotor-water surface distances.The performance of different modeling methods was analyzed based on the rotor experimental data of a diameter of 0.38 m,and the prediction results were quantified using the percentage of the mean-square error.The results show that the average error of the finite vortex rotor model is the smallest.Finally,a novel transition boundary is proposed to divide the rotor flow field of the gas–liquid mixture into two stages.The thrust loss zone is defined to delineate the safe operating range of the aircraft,providing a basis for the design of aerial-aquatic rotorcraft.
