As a multidisciplinary phenomenon,panel aeroelasticity in shock-dominated flow is featured by two primary interactions:Fluid-Structure Interactions(FSIs)and Shock-Boundary Layer Interactions(SBLIs).The former raises s...As a multidisciplinary phenomenon,panel aeroelasticity in shock-dominated flow is featured by two primary interactions:Fluid-Structure Interactions(FSIs)and Shock-Boundary Layer Interactions(SBLIs).The former raises structural concerns,and the latter is of aerodynamic interest.Thus,panel aeroelasticity in shock-dominated flow represents a vital topic for the development and optimization of supersonic vehicles and propulsion systems.This review systematically summarizes recent advances in the methodologies applied to capture structural and fluid dynamics,including theoretical models,numerical simulations,and wind tunnel experiments.The application of data-driven modal decomposition,an advanced technique to extract physically crucial features,on the topic is introduced.From the perspective of FSIs,the distinctive aeroelastic behaviors in shock-dominated flow,including hysteresis phenomena and nonlinear responses,are highlighted.From the perspective of SBLIs,the modifications in their spatial and temporal characteristics imposed by the aeroelastic responses are emphasized.Motivated by the interaction between the shock waves and structural response,different strategies have been proposed to implement aeroelastic suppression and shock control,which have the potential to enhance structural safety and aerodynamic performance in the next generation of high-speed flight vehicles.展开更多
A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade...A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade-Tip)rotor with TEF(Trailing Edge Flap)technology in forward flight.In the aspect of CSD method,the closed-form dynamical governing equation is modified using Hamilton’s principle to consider the influence of the movable TEF,in which the NTBT geometric nonlinearity is considered through coordinate transformation by virtue of finite element method.In the aspect of CFD method,a moving-embedded grid method for rotor blades is developed to account for the dynamic deflection of TEF,in which the grid deformation is achieved through algebraic transformations,and a high-precision unsteady CFD method with 5th-order TENO(Targeted Essentially Non-Oscillatory)scheme is introduced to effectively simulate the rotor flowfield.Considering the computational efficiency,the loosely-coupling strategy is introduced to build up the CFD/CSD method.The validity of the coupling method is verified by comparing the computed aerodynamic loads,frequency spectrum,and structural loads with the referential or the experimental results of the typical model rotors.Based on that,the frequency,phase,and amplitude-sweeping parametric analyses of TEF are conducted thoroughly to reveal the influence mechanisms on the aeroelastic characteristics of NTBT rotor.Furthermore,an optimal control strategy is proposed to suppress the vibration intensity of hub loads,showing that the active vibration reduction method can effectively suppress the rotor hub vibratory intensity by over 40%in typical forward flight conditions.展开更多
Aeroelastic control is a critical technique for high-aspect-ratio flexible wings.A novel aeroelastic control method is introduced,utilizing the internal Moving Mass Control(MMC)technique,which demonstrates the potenti...Aeroelastic control is a critical technique for high-aspect-ratio flexible wings.A novel aeroelastic control method is introduced,utilizing the internal Moving Mass Control(MMC)technique,which demonstrates the potential to fulfill hybrid control demands without incurring a drag penalty.Dynamic equations for a flexible wing equipped with a spanwise moving mass under unsteady aerodynamic loading are derived using mass position as the input variable.Controloriented analyses indicate that intrinsic structural frequencies,flutter characteristics,and gust response can be actively modified by varying the spanwise and chordwise positions of the mass element.Among these,the chordwise position exerts a more significant impact on the structural modes and flutter speed of the wing.A hybrid aeroelastic control system,incorporating motion planning and control law,is proposed to evaluate real-time performance in Active Flutter Suppression(AFS)and Gust Load Alleviation(GLA).Control outcomes suggest that,with a mass ratio of 1/16 and a half-chord installation area for the guide rail,flutter speed increases by about 10%.Additionally,excitation amplitudes across different gust frequencies are substantially mitigated,achieving a maximum reduction of vibration amplitude by about 73%.These findings offer a comprehensive understanding of the MMC technique and its application to flexible aircraft.展开更多
This study introduces a novel approach for coupled aeroelastic analysis of panel subjected to supersonic airflow,utilizing Add-On Acoustic Black Hole(AABH)to mitigate panel flutter.Employing Galerkin's method to d...This study introduces a novel approach for coupled aeroelastic analysis of panel subjected to supersonic airflow,utilizing Add-On Acoustic Black Hole(AABH)to mitigate panel flutter.Employing Galerkin's method to discretize aeroelastic equation of panel and leveraging finite element method to derive a reduced discrete model of AABH,this study effectively couples two substructures via interface displacement.Investigation into the interactive force highlights the modal effective mass,frequency discrepancy between oscillation and AABH mode,and modal damping ratio as critical factors influencing individual AABH mode in flutter suppression.The selection of effective AABH modes,closely linked to these factors,directly influences the accuracy of simulations.The results reveal that AABH notably enhances the panel's critical flutter boundary by14.6%,a significant improvement over the 3.6%increase afforded by equivalent mass.Furthermore,AABH outperforms both the tuned mass damper and nonlinear energy sink in flutter suppression efficacy.By adjusting the AABH's geometrical parameters to increase the accumulative modal effective mass within the pertinent frequency range,or choosing a suitable installation position for AABH,its performance in flutter suppression is further optimized.These findings not only underscore the AABH's potential in enhancing aeroelastic stability but also provide a foundation for its optimal design.展开更多
With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impa...With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.展开更多
Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An appr...Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation （LFT） representation of perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by using the structured singular value ,u-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.展开更多
The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish th...The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.展开更多
A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herei...A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herein is used to compute the non-planar aerodynamics of flexible wings with large deformation. The finite element method is introduced for structural nonlinear statics analysis. The surface spline method is used for structure/aerodynamics coupling. The static aeroelastic characteristics of the wind tunnel model of a flexible wing are studied by the nonlinear method presented, and the nonlinear method is also evaluated by comparing the results with those obtained from two other methods and the wind tunnel test. The results indicate that the traditional linear method of static aeroelastic analysis is not applicable for cases with large deformation because it produces results that are not realistic. However, the nonlinear methodology, which involves combining the structure finite element method with the non-planar vortex lattice method, could be used to solve the aeroelastic deformation with considerable accuracy, which is in fair agreement with the test results. Moreover, the nonlinear finite element method could consider complex structures. The non-planar vortex lattice method has advantages in both the computational accuracy and efficiency. Consequently, the nonlinear method presented is suitable for the rapid and efficient analysis requirements of engineering practice. It could be used in the preliminary stage and also in the detailed stage of aircraft design.展开更多
Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are ...Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are derived. The kinetic equation for aerodynamic force coupled with elastic movement is set up, and relevant formulae are derived. The unsteady aerodynamic one in that formulae is revised. The design principle, design process and range of application of such oscillating wing analytical method are elaborated. A flexible structural oscillating wing model is set up, and relevant time response analysis and frequency response analysis are conducted. The analytical results indicate that adopting the new-type driving way for the oscillating wing will not have flutter problems and will be able to produce propulsive force. Furthermore, it will consume much less power than the fixed wing for generating the same lift.展开更多
A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the tw...A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different non- linearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretical methods and aeroelastic flutter control methods are investigated in detail. The route to chaos and the cause of chaotic motion of two-dimensional aeroelastic system are summarized. Var- ious structural modeling methods for the high-aspect-ratio wing with geometric nonlinearity are dis- cussed. Accordingly, aerodynamic modeling approaches have been developed for the aeroelastic modeling of nonlinear high-aspect-ratio wings. Nonlinear aeroelasticity about high-altitude long- endurance （HALE） and fight aircrafts are studied separately. Finally, conclusions and the chal- lenges of the development in nonlinear aeroelasticity are concluded. Nonlinear aeroelastic problems of morphing wing, energy harvesting, and flapping aircrafts are proposed as new directions in the future.展开更多
The aeroelastic analysis of high-altitude,long-endurance(HALE)aircraft that features high-aspect-ratio flexible wings needs take into account structural geometrical nonlinearities and dynamic stall.For a generic nonli...The aeroelastic analysis of high-altitude,long-endurance(HALE)aircraft that features high-aspect-ratio flexible wings needs take into account structural geometrical nonlinearities and dynamic stall.For a generic nonlinear aeroelastic system,besides the stability boundary,the characteristics of the limit-cycle oscillation(LCO)should also be accurately predicted.In order to conduct nonlinear aeroelastic analysis of high-aspect-ratio flexible wings,a first-order,state-space model is developed by combining a geometrically exact,nonlinear anisotropic beam model with nonlinear ONERA(Edlin)dynamic stall model.The present investigations focus on the initiation and sustaining mechanism of the LCO and the effects of flight speed and drag on aeroelastic behaviors.Numerical results indicate that structural geometrical nonlinearities could lead to the LCO without stall occurring.As flight speed increases,dynamic stall becomes dominant and the LCO increasingly complicated.Drag could be negligible for LCO type,but should be considered to exactly predict the onset speed of flutter or LCO of high-aspect-ratio flexible wings.展开更多
A constrained adaptive neural network control scheme is proposed for a multi-input and multi-output（MIMO） aeroelastic system in the presence of wind gust,system uncertainties,and input nonlinearities consisting of i...A constrained adaptive neural network control scheme is proposed for a multi-input and multi-output（MIMO） aeroelastic system in the presence of wind gust,system uncertainties,and input nonlinearities consisting of input saturation and dead-zone.In regard to the input nonlinearities,the right inverse function block of the dead-zone is added before the input nonlinearities,which simplifies the input nonlinearities into an equivalent input saturation.To deal with the equivalent input saturation,an auxiliary error system is designed to compensate for the impact of the input saturation.Meanwhile,uncertainties in pitch stiffness,plunge stiffness,and pitch damping are all considered,and radial basis function neural networks（RBFNNs） are applied to approximate the system uncertainties.In combination with the designed auxiliary error system and the backstepping control technique,a constrained adaptive neural network controller is designed,and it is proven that all the signals in the closed-loop system are semi-globally uniformly bounded via the Lyapunov stability analysis method.Finally,extensive digital simulation results demonstrate the effectiveness of the proposed control scheme towards flutter suppression in spite of the integrated effects of wind gust,system uncertainties,and input nonlinearities.展开更多
The nonlinear aeroelastic behavior of a folding fin in supersonic flow is investigated in this paper.The finite element model of the fin is established and the deployable hinges are represented by three torsion spring...The nonlinear aeroelastic behavior of a folding fin in supersonic flow is investigated in this paper.The finite element model of the fin is established and the deployable hinges are represented by three torsion springs with the freeplay nonlinearity.The aerodynamic grid point is assumed to be at the center of each aerodynamic box for simplicity.The aerodynamic governing equation is given by using the infinite plate spline method and the modified linear piston theory.An improved fixed-interface modal synthesis method,which can reduce the rigid connections at the interface,is developed to save the problem size and computation time.The uniform temperature field is applied to create the thermal environment.For the linear flutter analyses,the flutter speed increases first and then decreases with the rise of the hinge stiffness due to the change of the flutter coupling mechanism.For the nonlinear analyses,a larger freeplay angle results in a higher vibration divergent speed.Two different types of limit cycle oscillations and a multiperiodic motion are observed in the wide range of airspeed under the linear flutter boundary.The linear flutter speed shows a slight descend in the thermal environment,but the effect of the temperature on the vibration divergent speed is different under different hinge stiffnesses when there exists freeplay.展开更多
This paper describes a method proposed for modeling large deflection of aircraft in nonlinear aeroelastic analysis by developing reduced order model（ROM）.The method is applied for solving the static aeroelastic and ...This paper describes a method proposed for modeling large deflection of aircraft in nonlinear aeroelastic analysis by developing reduced order model（ROM）.The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geometric nonlinearities;meanwhile,the non-planar effects of aerodynamics and follower force effect have been considered.ROMs are computational inexpensive mathematical representations compared to traditional nonlinear finite element method（FEM） especially in aeroelastic solutions.The approach for structure modeling presented here is on the basis of combined modal/finite element（MFE） method that characterizes the stiffness nonlinearities and we apply that structure modeling method as ROM to aeroelastic analysis.Moreover,the non-planar aerodynamic force is computed by the non-planar vortex lattice method（VLM）.Structure and aerodynamics can be coupled with the surface spline method.The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to analysis based on the FEM and experimental result.展开更多
A unified structural model for high-aspect-ratio composite wing with arbitrary cross-section is developed. Two types of lay-ups of the composite wing, namely, circumferentially uniform stiffness （CUS） configuration ...A unified structural model for high-aspect-ratio composite wing with arbitrary cross-section is developed. Two types of lay-ups of the composite wing, namely, circumferentially uniform stiffness （CUS） configuration and circumferentially asymmetric stiffness （CAS） configuration, are investigated. The present structural modeling method is validated through ANSYS FEM software for the case of a composite box beam. Then, the case of a single-cell composite wing with NACA0012 airfoil shape is considered. To investigate the aeroelastic problem of high-aspect-ratio composite wings, the linear ONERA aerodynamic model is used to model the unsteady aerodynamic loads under the case of small angle of attack. Finally, flutter speeds of the high-aspect-ratio wing with various composite ply angles are determined by using U-g method.展开更多
Recently, flutter active control using linear parameter varying（LPV） framework has attracted a lot of attention. LPV control synthesis usually generates controllers that are at least of the same order as the aeroela...Recently, flutter active control using linear parameter varying（LPV） framework has attracted a lot of attention. LPV control synthesis usually generates controllers that are at least of the same order as the aeroelastic models. Therefore, the reduced-order model is required by synthesis for avoidance of large computation cost and high-order controller. This paper proposes a new procedure for generation of accurate reduced-order linear time-invariant（LTI） models by using system identification from flutter testing data. The proposed approach is in two steps. The well-known poly-reference least squares complex frequency（p-LSCF） algorithm is firstly employed for modal parameter identification from frequency response measurement. After parameter identification,the dominant physical modes are determined by clear stabilization diagrams and clustering technique. In the second step, with prior knowledge of physical poles, the improved frequencydomain maximum likelihood（ML） estimator is presented for building accurate reduced-order model. Before ML estimation, an improved subspace identification considering the poles constraint is also proposed for initializing the iterative procedure. Finally, the performance of the proposed procedure is validated by real flight flutter test data.展开更多
A massive parallel aeroelastic simulation platform has been built to investigate the first1.5-stage fan of an aeroengine at rotating stall.The Computational Fluid Dynamics(CFD)solver and Computational Structural Dynam...A massive parallel aeroelastic simulation platform has been built to investigate the first1.5-stage fan of an aeroengine at rotating stall.The Computational Fluid Dynamics(CFD)solver and Computational Structural Dynamics(CSD)solver are coupled directly by non-matching mesh interfaces.The unsteady rotor/stator interaction is solved by the Sliding Mesh Interface method.The original rotor blades are shrouded by the midspan shrouds.An unshrouded fan is also created to investigate the effects of the midspan shrouds.Both the shrouded fan and unshrouded fan have stable aeroelasticity at the designed state.At rotating stall,the stalled region rotates at 30%of the rotor speed on the absolute reference frame.The energy spectrum of the rotating stalled flow is measured quantitatively.It shows that the first two order excitations are much stronger than the higher order excitations.In the flow of rotating stall,the fifth backward travelling wave mode of shrouded fan is resonated by the fifth excitation of the rotational stalled flow because the rotational speed of the stalled region coincides with the modal rotational speed,while for the unshrouded fan,the first bending mode is resonated by the second excitation of the rotational stalled flow,forming two waves in the circumference of the annulus blades.At rotating stall,the vibration of the shrouded blades is still under control but the vibration of the unshrouded blades is diverged and out of control.A novel tool,i.e.,resonance map,is proposed to predict the resonance.It provides a perspective to explain the effects of midspan shrouds at a theoretical level,and it would also be helpful in the structural design of blades.展开更多
Based on modified Leishman-Beddoes(L-B)state space model at low Mach number(lower than 0.3),the airfoil aeroelastic system is presented in this paper.The main modifications for L-B model include a new dynamic stall cr...Based on modified Leishman-Beddoes(L-B)state space model at low Mach number(lower than 0.3),the airfoil aeroelastic system is presented in this paper.The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient.The bifurcation diagrams,the limit cycle oscillation(LCO)phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry.It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall,and the asymmetric periodical oscillation,which is caused by the interaction of dynamic stall and static divergence,only happens in the airfoil aeroelastic system with asymmetry.Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively.Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate,which can be applied to the investigation of airfoil stall flutter at low Mach number.展开更多
Based on FEM theory,a method of dynamic analysis for hingeless rotors considering anisotropic composite materials is established.A parametric modeling method of composite blade with typical profile and high simulation...Based on FEM theory,a method of dynamic analysis for hingeless rotors considering anisotropic composite materials is established.A parametric modeling method of composite blade with typical profile and high simulation degree for design is proposed.Through the finite element method,the profile characteristics of rotor blade can be obtained efficiently and accurately,and the synchronization of parametric design and finite element analysis of structural characteristics can be realized.Then a 23-degrees of freedom non-linear beam element is used to simulate the extended one-dimensional beam,thereby a nonlinear differential equation describing the elastic motion of the rotor is established.To obtain the crosssectional target characteristics of the blades,an inverse design method is proposed for cross-section components based on combinatorial optimization algorithm.The calculation and validation work show that the proposed model can effectively analyze the aeroelastic characteristics of general composite rotors.Further,the influence of cross-sectional parameters on the aeroelastic stability and hub loads of hingeless rotor is analyzed and some remarkable conclusions are obtained.展开更多
The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existi...The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existing full-span models and improve the precision of aeroelastic analysis of tiltrotor aircraft in forward flight, the aeroelastic stability analysis model of full-span tiltrotor aircraft in forward flight has been presented in this paper by considering the coupling among elastic blade, wing, fuselage and various components. The analytical model is validated by comparing with the calculation results and experimental data in the existing references. The influence of some structural parameters, such as the fuselage degrees of freedom, relative displacement between the hub center and the gravity center, and nacelle length, on the system stability is also investigated. The results show that the fuselage degrees of freedom decrease the critical stability velocity of tiltrotor aircraft, and the variation of the structural parameters has great influence on the system stability,and the instability form of system can change between the anti-symmetric and symmetric wing motions of vertical and chordwise bending.展开更多
基金supported by the National Natural Science Foundation of China(No.12372233)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.25GH01020005)the“111 Project”of China(No.B17037)。
文摘As a multidisciplinary phenomenon,panel aeroelasticity in shock-dominated flow is featured by two primary interactions:Fluid-Structure Interactions(FSIs)and Shock-Boundary Layer Interactions(SBLIs).The former raises structural concerns,and the latter is of aerodynamic interest.Thus,panel aeroelasticity in shock-dominated flow represents a vital topic for the development and optimization of supersonic vehicles and propulsion systems.This review systematically summarizes recent advances in the methodologies applied to capture structural and fluid dynamics,including theoretical models,numerical simulations,and wind tunnel experiments.The application of data-driven modal decomposition,an advanced technique to extract physically crucial features,on the topic is introduced.From the perspective of FSIs,the distinctive aeroelastic behaviors in shock-dominated flow,including hysteresis phenomena and nonlinear responses,are highlighted.From the perspective of SBLIs,the modifications in their spatial and temporal characteristics imposed by the aeroelastic responses are emphasized.Motivated by the interaction between the shock waves and structural response,different strategies have been proposed to implement aeroelastic suppression and shock control,which have the potential to enhance structural safety and aerodynamic performance in the next generation of high-speed flight vehicles.
基金supported by the National Natural Science Foundation of China(Nos.12102186,12472237)the Young Elite Scientists Sponsorship Program by CAST,China(No.2022QNRC001)+1 种基金the National Key Laboratory Foundation of China(No.61422202201)the Aeronautical Science Foundation of China(No.2024Z010052002)。
文摘A high-precision CFD/CSD(Computational Fluid Dynamics/Computational Structural Dynamics)coupling method is developed to study the aeroelastic behavior and design the vibration reduction strategy of NTBT(New Type Blade-Tip)rotor with TEF(Trailing Edge Flap)technology in forward flight.In the aspect of CSD method,the closed-form dynamical governing equation is modified using Hamilton’s principle to consider the influence of the movable TEF,in which the NTBT geometric nonlinearity is considered through coordinate transformation by virtue of finite element method.In the aspect of CFD method,a moving-embedded grid method for rotor blades is developed to account for the dynamic deflection of TEF,in which the grid deformation is achieved through algebraic transformations,and a high-precision unsteady CFD method with 5th-order TENO(Targeted Essentially Non-Oscillatory)scheme is introduced to effectively simulate the rotor flowfield.Considering the computational efficiency,the loosely-coupling strategy is introduced to build up the CFD/CSD method.The validity of the coupling method is verified by comparing the computed aerodynamic loads,frequency spectrum,and structural loads with the referential or the experimental results of the typical model rotors.Based on that,the frequency,phase,and amplitude-sweeping parametric analyses of TEF are conducted thoroughly to reveal the influence mechanisms on the aeroelastic characteristics of NTBT rotor.Furthermore,an optimal control strategy is proposed to suppress the vibration intensity of hub loads,showing that the active vibration reduction method can effectively suppress the rotor hub vibratory intensity by over 40%in typical forward flight conditions.
基金supported by the National Natural Science Foundation of China(No.12102096)the Guangdong Basic and Applied Basic Research Foundation,China(No.2022A1515011885)the Research Fund of National Key Laboratory of Aerospace Physics in Fluids,China(No.2024-APF-KFQMJJ-08)。
文摘Aeroelastic control is a critical technique for high-aspect-ratio flexible wings.A novel aeroelastic control method is introduced,utilizing the internal Moving Mass Control(MMC)technique,which demonstrates the potential to fulfill hybrid control demands without incurring a drag penalty.Dynamic equations for a flexible wing equipped with a spanwise moving mass under unsteady aerodynamic loading are derived using mass position as the input variable.Controloriented analyses indicate that intrinsic structural frequencies,flutter characteristics,and gust response can be actively modified by varying the spanwise and chordwise positions of the mass element.Among these,the chordwise position exerts a more significant impact on the structural modes and flutter speed of the wing.A hybrid aeroelastic control system,incorporating motion planning and control law,is proposed to evaluate real-time performance in Active Flutter Suppression(AFS)and Gust Load Alleviation(GLA).Control outcomes suggest that,with a mass ratio of 1/16 and a half-chord installation area for the guide rail,flutter speed increases by about 10%.Additionally,excitation amplitudes across different gust frequencies are substantially mitigated,achieving a maximum reduction of vibration amplitude by about 73%.These findings offer a comprehensive understanding of the MMC technique and its application to flexible aircraft.
基金the National Key Research and Development Program of China(No.2021YFB3400100)the National Natural Science Foundation of China(Nos.52235003&U2241261)。
文摘This study introduces a novel approach for coupled aeroelastic analysis of panel subjected to supersonic airflow,utilizing Add-On Acoustic Black Hole(AABH)to mitigate panel flutter.Employing Galerkin's method to discretize aeroelastic equation of panel and leveraging finite element method to derive a reduced discrete model of AABH,this study effectively couples two substructures via interface displacement.Investigation into the interactive force highlights the modal effective mass,frequency discrepancy between oscillation and AABH mode,and modal damping ratio as critical factors influencing individual AABH mode in flutter suppression.The selection of effective AABH modes,closely linked to these factors,directly influences the accuracy of simulations.The results reveal that AABH notably enhances the panel's critical flutter boundary by14.6%,a significant improvement over the 3.6%increase afforded by equivalent mass.Furthermore,AABH outperforms both the tuned mass damper and nonlinear energy sink in flutter suppression efficacy.By adjusting the AABH's geometrical parameters to increase the accumulative modal effective mass within the pertinent frequency range,or choosing a suitable installation position for AABH,its performance in flutter suppression is further optimized.These findings not only underscore the AABH's potential in enhancing aeroelastic stability but also provide a foundation for its optimal design.
基金supported by the Natural Science Foundation of Shandong Provincial of China(Grant Number ZR2022ME093)the Natural Science Foundation of China(Grant Number 51675315).
文摘With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.
基金National Natural Science Foundation of China (10432040, 90716006)
文摘Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation （LFT） representation of perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by using the structured singular value ,u-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.
文摘The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.
基金National Natural Science Foundation of China(Nos.11172025,91116005)Research Fund for the Doctoral Program of Higher Education of China(No.20091102110015)
文摘A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herein is used to compute the non-planar aerodynamics of flexible wings with large deformation. The finite element method is introduced for structural nonlinear statics analysis. The surface spline method is used for structure/aerodynamics coupling. The static aeroelastic characteristics of the wind tunnel model of a flexible wing are studied by the nonlinear method presented, and the nonlinear method is also evaluated by comparing the results with those obtained from two other methods and the wind tunnel test. The results indicate that the traditional linear method of static aeroelastic analysis is not applicable for cases with large deformation because it produces results that are not realistic. However, the nonlinear methodology, which involves combining the structure finite element method with the non-planar vortex lattice method, could be used to solve the aeroelastic deformation with considerable accuracy, which is in fair agreement with the test results. Moreover, the nonlinear finite element method could consider complex structures. The non-planar vortex lattice method has advantages in both the computational accuracy and efficiency. Consequently, the nonlinear method presented is suitable for the rapid and efficient analysis requirements of engineering practice. It could be used in the preliminary stage and also in the detailed stage of aircraft design.
基金National Natural Science Foundation of China(10432040, 90716006)
文摘Making use of modal characteristics of the natural vibration of flexible structure to design the oscillating wing aircraft is proposed. A series of equations concerning the oscillating wing of flexible structures are derived. The kinetic equation for aerodynamic force coupled with elastic movement is set up, and relevant formulae are derived. The unsteady aerodynamic one in that formulae is revised. The design principle, design process and range of application of such oscillating wing analytical method are elaborated. A flexible structural oscillating wing model is set up, and relevant time response analysis and frequency response analysis are conducted. The analytical results indicate that adopting the new-type driving way for the oscillating wing will not have flutter problems and will be able to produce propulsive force. Furthermore, it will consume much less power than the fixed wing for generating the same lift.
基金the financial support of the National Natural Science Foundation of China (Nos.91116019 and 91216102)
文摘A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different non- linearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretical methods and aeroelastic flutter control methods are investigated in detail. The route to chaos and the cause of chaotic motion of two-dimensional aeroelastic system are summarized. Var- ious structural modeling methods for the high-aspect-ratio wing with geometric nonlinearity are dis- cussed. Accordingly, aerodynamic modeling approaches have been developed for the aeroelastic modeling of nonlinear high-aspect-ratio wings. Nonlinear aeroelasticity about high-altitude long- endurance （HALE） and fight aircrafts are studied separately. Finally, conclusions and the chal- lenges of the development in nonlinear aeroelasticity are concluded. Nonlinear aeroelastic problems of morphing wing, energy harvesting, and flapping aircrafts are proposed as new directions in the future.
基金National Natural Science Foundation of China(10272012)
文摘The aeroelastic analysis of high-altitude,long-endurance(HALE)aircraft that features high-aspect-ratio flexible wings needs take into account structural geometrical nonlinearities and dynamic stall.For a generic nonlinear aeroelastic system,besides the stability boundary,the characteristics of the limit-cycle oscillation(LCO)should also be accurately predicted.In order to conduct nonlinear aeroelastic analysis of high-aspect-ratio flexible wings,a first-order,state-space model is developed by combining a geometrically exact,nonlinear anisotropic beam model with nonlinear ONERA(Edlin)dynamic stall model.The present investigations focus on the initiation and sustaining mechanism of the LCO and the effects of flight speed and drag on aeroelastic behaviors.Numerical results indicate that structural geometrical nonlinearities could lead to the LCO without stall occurring.As flight speed increases,dynamic stall becomes dominant and the LCO increasingly complicated.Drag could be negligible for LCO type,but should be considered to exactly predict the onset speed of flutter or LCO of high-aspect-ratio flexible wings.
基金supported by the National Natural Science Foundation of China(Nos.61473307 and 61304120)the Aeronautical Science Foundation of China(No. 20155896026)
文摘A constrained adaptive neural network control scheme is proposed for a multi-input and multi-output（MIMO） aeroelastic system in the presence of wind gust,system uncertainties,and input nonlinearities consisting of input saturation and dead-zone.In regard to the input nonlinearities,the right inverse function block of the dead-zone is added before the input nonlinearities,which simplifies the input nonlinearities into an equivalent input saturation.To deal with the equivalent input saturation,an auxiliary error system is designed to compensate for the impact of the input saturation.Meanwhile,uncertainties in pitch stiffness,plunge stiffness,and pitch damping are all considered,and radial basis function neural networks（RBFNNs） are applied to approximate the system uncertainties.In combination with the designed auxiliary error system and the backstepping control technique,a constrained adaptive neural network controller is designed,and it is proven that all the signals in the closed-loop system are semi-globally uniformly bounded via the Lyapunov stability analysis method.Finally,extensive digital simulation results demonstrate the effectiveness of the proposed control scheme towards flutter suppression in spite of the integrated effects of wind gust,system uncertainties,and input nonlinearities.
文摘The nonlinear aeroelastic behavior of a folding fin in supersonic flow is investigated in this paper.The finite element model of the fin is established and the deployable hinges are represented by three torsion springs with the freeplay nonlinearity.The aerodynamic grid point is assumed to be at the center of each aerodynamic box for simplicity.The aerodynamic governing equation is given by using the infinite plate spline method and the modified linear piston theory.An improved fixed-interface modal synthesis method,which can reduce the rigid connections at the interface,is developed to save the problem size and computation time.The uniform temperature field is applied to create the thermal environment.For the linear flutter analyses,the flutter speed increases first and then decreases with the rise of the hinge stiffness due to the change of the flutter coupling mechanism.For the nonlinear analyses,a larger freeplay angle results in a higher vibration divergent speed.Two different types of limit cycle oscillations and a multiperiodic motion are observed in the wide range of airspeed under the linear flutter boundary.The linear flutter speed shows a slight descend in the thermal environment,but the effect of the temperature on the vibration divergent speed is different under different hinge stiffnesses when there exists freeplay.
文摘This paper describes a method proposed for modeling large deflection of aircraft in nonlinear aeroelastic analysis by developing reduced order model（ROM）.The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geometric nonlinearities;meanwhile,the non-planar effects of aerodynamics and follower force effect have been considered.ROMs are computational inexpensive mathematical representations compared to traditional nonlinear finite element method（FEM） especially in aeroelastic solutions.The approach for structure modeling presented here is on the basis of combined modal/finite element（MFE） method that characterizes the stiffness nonlinearities and we apply that structure modeling method as ROM to aeroelastic analysis.Moreover,the non-planar aerodynamic force is computed by the non-planar vortex lattice method（VLM）.Structure and aerodynamics can be coupled with the surface spline method.The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to analysis based on the FEM and experimental result.
文摘A unified structural model for high-aspect-ratio composite wing with arbitrary cross-section is developed. Two types of lay-ups of the composite wing, namely, circumferentially uniform stiffness （CUS） configuration and circumferentially asymmetric stiffness （CAS） configuration, are investigated. The present structural modeling method is validated through ANSYS FEM software for the case of a composite box beam. Then, the case of a single-cell composite wing with NACA0012 airfoil shape is considered. To investigate the aeroelastic problem of high-aspect-ratio composite wings, the linear ONERA aerodynamic model is used to model the unsteady aerodynamic loads under the case of small angle of attack. Finally, flutter speeds of the high-aspect-ratio wing with various composite ply angles are determined by using U-g method.
基金co-supported by the National Natural Science Foundation of China (Nos. 61134004 and 61573289)Aeronautical Science Foundation of China (No. 20140753010)the Fundamental Research Funds for the Central Universities (No. 3102015BJ004)
文摘Recently, flutter active control using linear parameter varying（LPV） framework has attracted a lot of attention. LPV control synthesis usually generates controllers that are at least of the same order as the aeroelastic models. Therefore, the reduced-order model is required by synthesis for avoidance of large computation cost and high-order controller. This paper proposes a new procedure for generation of accurate reduced-order linear time-invariant（LTI） models by using system identification from flutter testing data. The proposed approach is in two steps. The well-known poly-reference least squares complex frequency（p-LSCF） algorithm is firstly employed for modal parameter identification from frequency response measurement. After parameter identification,the dominant physical modes are determined by clear stabilization diagrams and clustering technique. In the second step, with prior knowledge of physical poles, the improved frequencydomain maximum likelihood（ML） estimator is presented for building accurate reduced-order model. Before ML estimation, an improved subspace identification considering the poles constraint is also proposed for initializing the iterative procedure. Finally, the performance of the proposed procedure is validated by real flight flutter test data.
文摘A massive parallel aeroelastic simulation platform has been built to investigate the first1.5-stage fan of an aeroengine at rotating stall.The Computational Fluid Dynamics(CFD)solver and Computational Structural Dynamics(CSD)solver are coupled directly by non-matching mesh interfaces.The unsteady rotor/stator interaction is solved by the Sliding Mesh Interface method.The original rotor blades are shrouded by the midspan shrouds.An unshrouded fan is also created to investigate the effects of the midspan shrouds.Both the shrouded fan and unshrouded fan have stable aeroelasticity at the designed state.At rotating stall,the stalled region rotates at 30%of the rotor speed on the absolute reference frame.The energy spectrum of the rotating stalled flow is measured quantitatively.It shows that the first two order excitations are much stronger than the higher order excitations.In the flow of rotating stall,the fifth backward travelling wave mode of shrouded fan is resonated by the fifth excitation of the rotational stalled flow because the rotational speed of the stalled region coincides with the modal rotational speed,while for the unshrouded fan,the first bending mode is resonated by the second excitation of the rotational stalled flow,forming two waves in the circumference of the annulus blades.At rotating stall,the vibration of the shrouded blades is still under control but the vibration of the unshrouded blades is diverged and out of control.A novel tool,i.e.,resonance map,is proposed to predict the resonance.It provides a perspective to explain the effects of midspan shrouds at a theoretical level,and it would also be helpful in the structural design of blades.
基金Aeronautical Science Foundation of China(08A52003)Science and Technology Foundation of Rotorcraft Aeromechanics Laboratory(9140C4001010901)
文摘Based on modified Leishman-Beddoes(L-B)state space model at low Mach number(lower than 0.3),the airfoil aeroelastic system is presented in this paper.The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient.The bifurcation diagrams,the limit cycle oscillation(LCO)phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry.It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall,and the asymmetric periodical oscillation,which is caused by the interaction of dynamic stall and static divergence,only happens in the airfoil aeroelastic system with asymmetry.Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively.Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate,which can be applied to the investigation of airfoil stall flutter at low Mach number.
文摘Based on FEM theory,a method of dynamic analysis for hingeless rotors considering anisotropic composite materials is established.A parametric modeling method of composite blade with typical profile and high simulation degree for design is proposed.Through the finite element method,the profile characteristics of rotor blade can be obtained efficiently and accurately,and the synchronization of parametric design and finite element analysis of structural characteristics can be realized.Then a 23-degrees of freedom non-linear beam element is used to simulate the extended one-dimensional beam,thereby a nonlinear differential equation describing the elastic motion of the rotor is established.To obtain the crosssectional target characteristics of the blades,an inverse design method is proposed for cross-section components based on combinatorial optimization algorithm.The calculation and validation work show that the proposed model can effectively analyze the aeroelastic characteristics of general composite rotors.Further,the influence of cross-sectional parameters on the aeroelastic stability and hub loads of hingeless rotor is analyzed and some remarkable conclusions are obtained.
基金supported by the National Natural Science Foundation of China (No. 11572150)
文摘The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existing full-span models and improve the precision of aeroelastic analysis of tiltrotor aircraft in forward flight, the aeroelastic stability analysis model of full-span tiltrotor aircraft in forward flight has been presented in this paper by considering the coupling among elastic blade, wing, fuselage and various components. The analytical model is validated by comparing with the calculation results and experimental data in the existing references. The influence of some structural parameters, such as the fuselage degrees of freedom, relative displacement between the hub center and the gravity center, and nacelle length, on the system stability is also investigated. The results show that the fuselage degrees of freedom decrease the critical stability velocity of tiltrotor aircraft, and the variation of the structural parameters has great influence on the system stability,and the instability form of system can change between the anti-symmetric and symmetric wing motions of vertical and chordwise bending.
