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Dynamical Stability of Transonic Shock Solutions to Non-Isentropic Euler Equations 认领 引用
1
作者 Ben Duan Yan Zhou 《Communications in Mathematical Research》 CSCD 2025年第3期250-270,共21页
In this paper,we investigate the dynamical stability of transonic shock solutions for the full compressible Euler system in a two dimensional nozzle with a symmetric divergent part.Building upon the existence and uniq... In this paper,we investigate the dynamical stability of transonic shock solutions for the full compressible Euler system in a two dimensional nozzle with a symmetric divergent part.Building upon the existence and uniqueness results for steady symmetric transonic shock solutions to the nonisentropic Euler system established in[Z.P.Xin and H.C.Yin,The transonic shock in a nozzle,2-D and 3-D complete Euler systems,J.Differential Equations 245(2008)],we prove the dynamical stability of the transonic shock solutions under small perturbations.More precisely,if the initial unsteady transonic flow is located in the symmetric divergent part of the nozzle and the flow is a symmetric small perturbation of the steady transonic flow,we use the characteristic method to establish the dynamical stability. 展开更多
关键词 Euler equation transonic shock dynamical stability
DYNAMICAL STABILITY OF VISCOELASTIC COLUMN WITH FRACTIONAL DERIVATIVE CONSTITUTIVE RELATION 认领 引用 被引量：1
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作者 李根国 朱正佑 程昌钧 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2001年第3期294-303,共10页
The dynamic stability of simple supported viscoelastic column, subjected to a periodic axial force, is investigated. The viscoelastic material was assumed to obey the fractional derivative constitutive relation. The g... The dynamic stability of simple supported viscoelastic column, subjected to a periodic axial force, is investigated. The viscoelastic material was assumed to obey the fractional derivative constitutive relation. The governing equation of motion was derived as a weakly singular Volterra integro-partial-differential equation, and it was simplified into weakly singular Volterra integro-ordinary-differential equation by the Galerkin method. In terms of the averaging method, the dynamical stability was analyzed. A new numerical method is proposed to avoid storing all history data. Numerical examples are presented and the numerical results agree with the analytical ones. 展开更多
关键词 viscoelastic column fractional derivative constitutive relation averaging method weakly singular Volterra integro-differential equation dynamical stability
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Dynamical Stability of Finite Anisotropic Panels with Elliptical Cutouts and Cracks 认领 引用
3
作者 Zhao Qi 《Advances in Manufacturing》 EI CAS 1998年第1期38-42,共5页
An approximate analysis for dynamical stability of anisotropic finite panels with centrally located elliptical cutouts is presented. The analysis is divided into two parts: a plane stress analysis and a stability anal... An approximate analysis for dynamical stability of anisotropic finite panels with centrally located elliptical cutouts is presented. The analysis is divided into two parts: a plane stress analysis and a stability analysis. The plane stress distribution is determined by using Lekhnitskii's complex variable equations of plane elastostatics combined with a Laurent series approximation constructed by the conformal mapping and a boundary collocation method. Its solutions satisfy the conditions along the interior boundary and at a discrete number of points along the exterior panel ones. The stability analysis is conducted by using the differential equations which result from the Hamilton's principle and the classical plate theory. The relation of vibration frequency, load parameter and stability of panels is investigated by solving the fundamental equations using separation of variables, so as to obtain the critical loads. Finally, comparisons with documented experimental results and finite element analysis are made. Results of a parameter study are presented. 展开更多
关键词 dynamical stability anisotropic panel Lekhnitskii's eqnation Hamilton's principle
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On well-posed local-nonlocal mixed integral model of piezoelectricity for dynamic stability and vibration analysis of piezoelectric Timoshenko nanobeams with general boundary constraints 认领 引用
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作者 Pei ZHANG PSCHIAVONE +3 位作者 Luke ZHAO Dongbo LI Yanming REN Hai QING 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2026年第4期815-838,共24页
Existing research has shown that nonlocal piezoelectric differential models often yield inconsistent dynamic responses for nanostructures.To address this issue,the two-phase local-nonlocal integral formulation has bee... Existing research has shown that nonlocal piezoelectric differential models often yield inconsistent dynamic responses for nanostructures.To address this issue,the two-phase local-nonlocal integral formulation has been proposed and has garnered increasing scholarly attention as an effective alternative.This study presents the first implementation of this theoretically consistent and paradox-free framework to investigate the size-dependent dynamic stability and free vibration behavior in piezoelectric Timoshenko nanobeams.The generalized boundary conditions are simulated through elastic constraints incorporating both translational and rotational springs at both beam ends.Departing from conventional approaches,the present formulation simultaneously accounts for size effects in both bending deformation and axial deformation caused by external voltages via the derivation of an equivalent differential representation of the well-posed local-nonlocal integral piezoelectric model.This formulation is rigorously complemented by a complete set of constitutive constraint conditions,ensuring mathematical well-posedness.The generalized differential quadrature method(GDQM)is used to discretize the governing differential equations,enabling numerical determination of dynamic instability regions(DIRs)for various boundary configurations.Following comprehensive validation through comparative analyses,we systematically examine the influence of nonlocal parameters,static force factors,and boundary stiffness characteristics on the DIRs of the beams.Furthermore,this investigation underscores the significance of incorporating nonlocal effects into voltage-induced axial loading,addressing a critical gap in the current understanding of electromechanical coupling at nanoscale dimensions. 展开更多
关键词 two-phase nonlocal integral model piezoelectric beam dynamic stability nonlocal axial force generalized differential quadrature method(GDQM)
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Dynamic stability of flapping-wing vehicles with different wing damage forms 认领 引用
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作者 Yuxin Xie Zengshuang Chen +1 位作者 Xueguang Meng Gang Chen 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第7期239-250,共12页
Investigating the dynamic stability of flapping-wing vehicles(FWVs)is a critical foundation for achieving insectlike agile flight control.Present studies on flight dynamic stability have focused on intact insects or F... Investigating the dynamic stability of flapping-wing vehicles(FWVs)is a critical foundation for achieving insectlike agile flight control.Present studies on flight dynamic stability have focused on intact insects or FWVs.Based on our previous work on the aerodynamics of different damaged wings,this study investigates the flight stability of four hovering damaged FWVs with different unilateral wing damage forms.All damaged FWVs suffered area loss in various locations of their right wings,with the lost area set as a uniform 20%of the wing surface.Results showed that under hovering flight conditions,the stability modal structures of all damaged FWVs remained unchanged in both longitudinal and lateral motions compared to the intact one.Meanwhile,the time constants and motions of each mode were similar to those of the intact one.Moreover,there was almost no difference in the stability characteristics among different damaged FWVs,which suggested that the location of wing area loss did not affect the dynamic stability of damaged FWVs.This work provides a reference for designing the control systems for FWVs coping with random wing damage. 展开更多
关键词 Dynamic stability Wing damage Computational fluid dynamics Bioinspired flight FWVs
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Investigation of flight stability for fixed canard dual-spin projectile via CFD/RBD coupled method 认领 引用
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作者 Gang Wang Tengyue Zhang +2 位作者 Tianyu Lin Haizhen Lin Ke Xi 《Defence Technology（防务技术）》 SCIE EI CAS CSCD 2025年第11期1-18,共18页
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj... In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability. 展开更多
关键词 Fixed canard dual-spin projectile CFD/RBD coupled method Virtualflight simulation Following stability Dynamic stability
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Coordinative motion planning for head stabilization of a bird-neck inspired flexible robot 认领 引用
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作者 Xiuting Sun Yipeng Qu +1 位作者 Jiawei Qian Jian Xu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第5期574-595,共22页
To address the critical challenge of end-effector stabilization in bipedal robots while enhancing upper-body motion flexibility,this study introduces a novel bionic fully-elastically-connected tensegrity robot(BFEC-TR... To address the critical challenge of end-effector stabilization in bipedal robots while enhancing upper-body motion flexibility,this study introduces a novel bionic fully-elastically-connected tensegrity robot(BFEC-TR)inspired by the biomechanics of avian cervical construction.The proposed design transcends conventional approaches by implementing a multinodes bionic tensegrity structure that enables superior spatial deformation capabilities,complemented by an innovative elastic muscle control strategy for dynamic stabilization across multiple locomotion gaits:swing,walking,and running.The study encompasses three key technical contributions.First,we establish a comprehensive dynamic model of the BFEC-TR through kinematic geometric analysis.Second,we develop a feedforward control strategy that explicitly addresses the dynamic requirements of various gaits by establishing the relationship between gait parameters and control parameters,thereby ensuring segmental coordination for head stabilization.Within this control framework,we derive an optimal configuration that maintains bionic posture under energy-efficient driving criteria.Finally,extensive experimental validation demonstrates the efficacy of the proposed control strategy across different locomotion gaits.This work provides biologically-inspired design paradigm and control methodology to achieve spatial dynamic stabilization for bipedal robot end-effectors.The integration of tensegrity principles with biological inspiration from avian neck mechanics presents a novel direction for enhancing the performance and adaptability of robotic systems in dynamic environments. 展开更多
关键词 Neck-bioinspired robot Tensegrity flexible structure Dynamic stabilization Feedforward control Motion planning
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Compact formulation of the augmented evolution equation for optimal control computation 认领 引用
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作者 Sheng Zhang Jiangtao Huang +2 位作者 Gang Liu Fei Liao Fangfang Hu 《Control Theory and Technology》 EI CSCD 2026年第1期96-110,共15页
The augmented evolution equation is established under the framework of the Variation Evolving Method(VEM)that seeks optimal solutions by solving the transformed Initial-Value Problems(IVPs).To improve the numerical pe... The augmented evolution equation is established under the framework of the Variation Evolving Method(VEM)that seeks optimal solutions by solving the transformed Initial-Value Problems(IVPs).To improve the numerical performance,its compact form is developed herein.Through replacing the states and costates variation evolution with that of the controls,the dimension-reduced Evolution Partial Differential Equation(EPDE)only solves the control variables along the variation time to get the optimal solution,and the initial conditions for the definite solution may be arbitrary.With this equation,the scale of the resulting IVPs,obtained via the semi-discrete method,is significantly reduced and they may be solved with common Ordinary Differential Equation(ODE)integration methods conveniently.Meanwhile,the state and the costate dynamics share consistent stability in the numerical computation and this avoids the intrinsic numerical difficulty as in the indirect methods.Numerical examples are solved and it is shown that the compact form evolution equation outperforms the primary form in the precision,and the efficiency may be higher for the dense discretization.Actually,it is uncovered that the compact form of the augmented evolution equation is a continuous realization of the Newton type iteration mechanism. 展开更多
关键词 Optimal control Lyapunov dynamics stability Variation evolution Evolution partial differential equation Initial-value problem
Quantized vortices in spinor Bose–Einstein condensates with time–space modulated interactions and stability analysis 认领 引用
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作者 Yu-Qin Yao Ji Li 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第10期227-232,共6页
The three-component Gross–Pitaevskii equation with an angular momentum rotational term can be served as a model to study spinor Bose–Einstein condensates (BECs) with time–space modulated interactions. Vortex soluti... The three-component Gross–Pitaevskii equation with an angular momentum rotational term can be served as a model to study spinor Bose–Einstein condensates (BECs) with time–space modulated interactions. Vortex solutions of the spinor BECs with spatiotemporally modulated interactions are worked out by similarity transformation. Theoretical analysis and numerical simulation of vortex states are demonstrated. Stable vortex states are obtained by adjusting the frequency of the external potential and the spatiotemporally modulated interaction. 展开更多
关键词 spinor Bose-Einstein condensates spatiotemporal modulation vortex solution dynamical stability
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Context-Adaptive and Physics-Consistent Constrained Multimodal Interpretable Remaining Useful Life Prediction 认领 引用
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作者 Yu Wang Yabin Wang +4 位作者 Liang Wen Bingyu Li Mengze Qin Fang Li Zhonghua Cheng 《Computers, Materials & Continua》 SCIE EI 2026年第6期1899-1918,共20页
Remaining useful life(RUL)prediction for complex equipment is a critical technology for ensuring the safe and reliable operation of industrial systems.However,existing data-driven models commonly suffer from limitatio... Remaining useful life(RUL)prediction for complex equipment is a critical technology for ensuring the safe and reliable operation of industrial systems.However,existing data-driven models commonly suffer from limitations such as weak cross-operational condition generalization,insufficient physical interpretability,and unstable training on non-stationary time-series data.To address these challenges,this paper proposes a temporal degradation prediction model that integrates context adaptation and physics-consistent constraints,named the Context-Adaptive Physics-informed Time-aware meta-Network(CAPTAIN).The model incorporates four core components:a Context-Aware Meta-Learning(CAML)module that enables lightweight parameter adaptation to diverse scenarios;Physics-Informed Neural Network(PINN)constraints that uniformly characterize deterministic degradation dynamics and stochastic Wiener process perturbations;a three-layer dynamic stabilization training strategy comprising temporal meta-training,residual adaptive refinement,and exponential moving average to ensure training stability;and a multimodal interpretability framework integrating LIME,GradCAM,GradCAM_LW,Integrated Gradients,and KernelSHAP to enhance prediction transparency.Extensive experiments on the NASA C-MAPSS datasets(FD001-FD004)demonstrate that CAPTAIN achieves state-of-the-art performance under both single/multiple failure modes and steady/varying operating conditions,with an average RMSE of 12.02±0.98 and an average SCORE of 487.50±23.0,outperforming ten advanced baseline models.The model exhibits exceptional generalization capability across different operational conditions and strong robustness in scenarios with coupled multiple faults.Multimodal visualizations and quantitative assessments verify its interpretability advantages,showing high consistency with the physical degradation laws of engines.This work provides a reliable paradigm for RUL prediction of complex equipment,combining the flexibility of data-driven modeling with the credibility of physical modeling. 展开更多
关键词 Remaining useful life prediction physics-informed neural networks context adaptation meta-learning multimodal interpretability dynamic stabilization training
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Manipulation of Topological Boundaries within a Magnetic Domain Wall 认领 引用
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作者 Zhuyang Nie Ji Chen +6 位作者 Cunlong Dong Bin He Caihua Wan Haifeng Du Xiufeng Han Yizhou Liu Guoqiang Yu 《Chinese Physics Letters》 SCIE EI CAS CSCD 2026年第5期277-292,共16页
Bloch points and transverse walls can serve as topological boundaries within a magnetic domain wall.Here,we investigate the stability and dynamics of these topological boundaries for potential spintronic applications.... Bloch points and transverse walls can serve as topological boundaries within a magnetic domain wall.Here,we investigate the stability and dynamics of these topological boundaries for potential spintronic applications.Using micromagnetic simulations,we reveal the coexistence regimes of Bloch points and transverse walls in thin films with perpendicular magnetic anisotropy.An external in-plane field enables reversible transitions between these states through boundary-mediated Bloch point nucleation and annihilation processes.Under spin-transfer torque,transverse walls exhibit transverse drift and deformation.In contrast,Bloch points move strictly along the domain wall without transverse deflection and feature a Walker breakdown threshold an order of magnitude higher than conventional domain walls.Our findings establish a device concept where binary states correspond to in-plane magnetization orientations separated by mobile topological boundaries,offering new opportunities for spintronic architectures. 展开更多
关键词 bloch points transverse walls magnetic domain wallherewe topological boundaries micromagnetic simulationswe magnetic domain walls thin films stability dynamics
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Model test and numerical simulation on the dynamic stability of the bedding rock slope under frequent microseisms 认领 引用 被引量：17
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作者 Deng Zhiyun Liu Xinrong +4 位作者 Liu Yongquan Liu Shulin Han Yafeng Liu Jinhui Tu Yiliang 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2020年第4期919-935,共17页
Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability... Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability under purely microseisms and the influence of five factors, including seismic amplitude, slope height, slope angle, strata inclination and strata thickness, were considered. The experimental results show that the natural frequency of the slope decreases and damping ratio increases as the earthquake loading times increase. The dynamic strength reduction method is adopted for the stability evaluation of the bedding rock slope in numerical simulation, and the slope stability decreases with the increase of seismic amplitude, increase of slope height, reduction of strata thickness and increase of slope angle. The failure mode of a mid-dip bedding rock slope in the shaking table test is integral slipping along the bedding surface with dipping tensile cracks at the slope rear edge going through the bedding surfaces. In the numerical simulation, the long-term stability of a mid-dip bedding slope is worst under frequent microseisms and the slope is at risk of integral sliding instability, whereas the slope rock mass is more broken than shown in the shaking table test. The research results are of practical significance to better understand the formation mechanism of reservoir landslides and prevent future landslide disasters. 展开更多
关键词 bedding rock slope frequent microseisms shaking table test numerical simulation dynamic stability failure mode long-term stability
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Real-time Tire Parameters Observer for Vehicle Dynamics Stability Control 认领 引用 被引量：11
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作者 LI Liang LI Hongzhi +2 位作者 ZHANG Xiaolong HE Lin SONG Jian 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS 2010年第5期620-626,共7页
The performance of the vehicle dynamics stability control system(DSC)is dominated by the accurate estimation of tire forces in real-time.The characteristics of tire forces are determined by tire dynamic states and par... The performance of the vehicle dynamics stability control system(DSC)is dominated by the accurate estimation of tire forces in real-time.The characteristics of tire forces are determined by tire dynamic states and parameters,which vary in an obviously large scope along with different working conditions.Currently,there have been many methods based on the nonlinear observer to estimate the tire force and dynamic parameters,but they were only used in off-line analysis because of the computation complexity and the dynamics differences of four tires in the steering maneuver conditions were not considered properly.This paper develops a novel algorithm to observe tire parameters in real-time controller for DSC.The algorithm is based on the sensor-fusion technology with the signals of DSC sensors,and the tire parameters are estimated during a set of maneuver courses.The calibrated tire parameters in the control cycle are treated as the elementary states for vehicle dynamics observation,in which the errors between the calculated and the measured vehicle dynamics are used as the correcting factors for the tire parameter observing process.The test process with a given acceleration following a straight line is used to validate the estimation method of the longitudinal stiffness;while the test process with a given steering angle is used to validate the estimated value of the cornering stiffness.The ground test result shows that the proposed algorithm can estimate the tire stiffness accurately with an acceptable computation cost for real-time controller only using DSC sensor signal.The proposed algorithm can be an efficient algorithm for estimating the tire dynamic parameters in vehicle dynamics stability control system,and can be used to improve the robustness of the DSC controller. 展开更多
关键词 tire longitudinal stiffness cornering stiffness vehicle dynamics stability
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Light-Induced Dynamic Stability of Oxygen Vacancies in BiSbO4for Efficient Photocatalytic Formaldehyde Degradation 认领 引用 被引量：5
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作者 Maoxi Ran Wen Cui +4 位作者 Kanglu Li Lvcun Chen Yuxin Zhang Fan Dong Yanjuan Sun 《Energy & Environmental Materials》 SCIE EI CAS CSCD 2022年第1期305-312,共8页
Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity.However,there are a few studies concerning how to maintain the stability of defects,which is important to ensure sus... Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity.However,there are a few studies concerning how to maintain the stability of defects,which is important to ensure sustainable photocatalytic performance.Here,a novel strategy to modulate the structural properties of BiSbO4using light-induced dynamic oxygen vacancies is reported by us for efficient and stable photocatalytic oxidation of formaldehyde.Interestingly,the continuous consumption and replenishment of vacancies(namely dynamic vacancies)ensure the dynamic stability of oxygen vacancies,thus guaranteeing the excellent photocatalytic stability.The oxygen vacancies could also accelerate the electron migration,inhibit the photogenerated electron/hole recombination,widen the light absorption spectra,and thus improve the photocatalytic formaldehyde removal performance.Combined with the results of in situ DRIFTS,the reaction mechanism for each step of formaldehyde oxidation is revealed.As supported by DFT calculation of Gibbs free energy,the introduction of oxygen vacancies into BiSbO4can promote spontaneous process of formaldehyde oxidation.Our work highlights a promising approach for stabilizing the defects and proposes the photocatalytic reaction mechanism in combination with the thermodynamic functions. 展开更多
关键词 dynamic stability formaldehyde degradation oxygen vacancy photocatalysis reaction mechanism
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DYNAMIC STABILITY ANALYSIS OF EMBEDDED MULTI-WALLED CARBON NANOTUBES IN THERMAL ENVIRONMENT 认领 引用 被引量：3
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作者 R.Ansari R.Gholami +2 位作者 S.Sahmani A.Norouzzadeh M.Bazdid-Vahdati 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2015年第6期659-667,共9页
In the present paper, the dynamic stability of multi-walled carbon nanotubes （MW- CNTs） embedded in an elastic medium is investigated including thermal environment effects. To this end, a nonlocal Timoshenko beam mo... In the present paper, the dynamic stability of multi-walled carbon nanotubes （MW- CNTs） embedded in an elastic medium is investigated including thermal environment effects. To this end, a nonlocal Timoshenko beam model is developed which captures small scale effects. Dynamic governing equations of the carbon nanotubes are formulated based on the Timoshenko beam theory including the effects of axial compressive force. Then a parametric study is conducted to investigate the influences of static load factor, temperature change, nonlocal parameter, slenderness ratio and spring constant of the elastic medium on the dynamic stability characteristics of MWCNTs with simply-supported end supports. 展开更多
关键词 multi-walled carbon nanotubes dynamic stability nonlocal elasticity thermal environment small scale effect
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Dynamic flight stability of a bumblebee in forward flight 认领 引用 被引量：11
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作者 Yan Xiong Mao Sun 《Acta Mechanica Sinica》 SCIE EI CAS 2008年第1期25-36,共12页
The longitudinal dynamic flight stability of a bumblebee in forward flight is studied.The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eige... The longitudinal dynamic flight stability of a bumblebee in forward flight is studied.The method of computational fluid dynamics is used to compute the aerodynamic derivatives and the techniques of eigenvalue and eigenvector analysis are employed for solving the equations of motion.The primary findings are as the following.The forward flight of the bumblebee is not dynamically stable due to the existence of one(or two)unstable or approximately neutrally stable natural modes of motion.At hovering to medium flight speed[flight speed Ue=(0-3.5)m s^-1;advance ratio J=0-0.44],the flight is weakly unstable or approximately neutrally stable;at high speed(Ue=4.5 m s^-1;J=0.57),the flight becomes strongly unstable(initial disturbance double its value in only 3.5 wingbeats). 展开更多
关键词 Bumblebee Dynamic stability Forward flight Navier-Stokes simulation Natural modes of motion
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Dynamic flight stability of a hovering model insect:lateral motion 认领 引用 被引量：20
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作者 Yanlai Zhang Mao Sun 《Acta Mechanica Sinica》 SCIE EI CAS 2010年第2期175-190,共16页
The lateral dynamic flight stability of a hovering model insect(dronefly)was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvect... The lateral dynamic flight stability of a hovering model insect(dronefly)was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion.The main results are as following.(i)Three natural modes of motion were identified:one unstable slow divergence mode(mode 1),one stable slow oscillatory mode(mode 2),and one stable fast subsidence mode(mode 3).Modes 1 and 2 mainly consist of a rotation about the horizontal longitudinal axis(x-axis)and a side translation;mode 3 mainly consists of a rotation about the x-axis and a rotation about the vertical axis.(ii)Approximate analytical expressions of the eigenvalues are derived,which give physical insight into the genesis of the natural modes of motion.(iii)For the unstable divergence mode,td,the time for initial disturbances to double,is about 9 times the wingbeat period(the longitudinal motion of the model insect was shown to be also unstable and td of the longitudinal unstable mode is about 14 times the wingbeat period).Thus,although the flight is not dynamically stable,the instability does not grow very fast and the insect has enough time to control its wing motion to suppress the disturbances. 展开更多
关键词 Insect Dynamic flight stability Hovering·Lateral motion Natural modes of motion
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Dynamic Stability and Fuzzy Reliability Analysis of Toppling Perilous Rock Under Seismic Excitation 认领 引用 被引量：2
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作者 Linfeng Wang Jixu Zhang +2 位作者 Wanchun Xia Xiaoming Huang Guojin Tan 《Journal of Earth Science》 SCIE CAS CSCD 2024年第1期248-262,共15页
To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under... To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under the action of bidirectional earthquakes is proposed.First,the mass viscoelasticity model is used to simulate two main control surfaces of toppling perilous rock,the seismic dynamic response model and motion equation of toppling perilous rock are established based on the D'Alembert principle,and the Newmark-β method is used to solve the dynamic motion equation.Then,the instability event of toppling perilous rock is considered a fuzzy event,the membership function expression of the stability coefficient of toppling perilous rock is determined based on the fuzzy failure criterion,the calculation equations of the toppling perilous rock dynamic stability coefficient and fuzzy reliability are established,and the fuzzy reliability evaluation method based on the probability distribution of reliability is proposed.Finally,the influence of different superposition modes of seismic excitation on the fuzzy reliability of toppling perilous rock is analyzed.The calculation results of toppling perilous rock in the engineering case show that the fuzzy reliability calculated after considering the fuzzy failure criterion is reduced by 10.73% to 25.66% compared with the classical reliability.Considering the bidirectional seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 5.46% to 14.89%.Compared with using the acceleration peak time encounter mode to superpose the seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 3.4% when the maximum action effect time encounter mode is adopted. 展开更多
关键词 toppling perilous rock bidirectional earthquake fuzzy failure criterion dynamic stability fuzzy reliability Newmark-βmethod probability distribution function
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Dynamic flight stability of hovering model insects:theory versus simulation using equations of motion coupled with Navier-Stokes equations 认领 引用 被引量：10
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作者 Yan-Lai Zhang Mao Sun 《Acta Mechanica Sinica》 SCIE EI CAS 2010年第4期509-520,共12页
In the present paper,the longitudinal dynamic flight stability properties of two model insects are predicted by an approximate theory and computed by numerical sim-ulation.The theory is based on the averaged model(whi... In the present paper,the longitudinal dynamic flight stability properties of two model insects are predicted by an approximate theory and computed by numerical sim-ulation.The theory is based on the averaged model(which assumes that the frequency of wingbeat is sufficiently higher than that of the body motion,so that the flapping wings'degrees of freedom relative to the body can be dropped and the wings can be replaced by wingbeat-cycle-average forces and moments);the simulation solves the complete equations of motion coupled with the Navier-Stokes equations.Comparison between the theory and the simulation provides a test to the validity of the assumptions in the theory.One of the insects is a model dronefly which has relatively high wingbeat frequency(164 Hz)and the other is a model hawkmoth which has relatively low wingbeat frequency(26 Hz).The results show that the averaged model is valid for the hawkmoth as well as for the dronefly.Since the wingbeat frequency of the hawkmoth is relatively low(the characteristic times of the natural modes of motion of the body divided by wingbeat period are relatively large)compared with many other insects,that the theory based on the averaged model is valid for the hawkmoth means that it could be valid for many insects. 展开更多
关键词 Insect Hovering Dynamic flight stability Averaged model Equations-of-motion Navier-Stokes simulation
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Dynamic Flight Stability of a Model Hoverfly in Inclined-Stroke-Plane Hovering 认领 引用 被引量：12
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作者 Xiaolei Mou Mao Sun 《Journal of Bionic Engineering》 SCIE EI CSCD 2012年第3期294-303,共10页
Most hovering insects flap their wings in a horizontal plane, called ＇normal hovering＇. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudina... Most hovering insects flap their wings in a horizontal plane, called ＇normal hovering＇. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane. In the present paper, the longitudinal dynamic flight stability of a model hoverfly in inclined-stroke-plane hovering was studied. Computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was used to solve the equations of motion. The primary findings are as follows. （1） For inclined-stroke-plane hovering, the same three natural modes of motion as those for normal hovering were identified： one unstable oscillatory mode, one stable fast subsidence mode, and one stable slow subsidence mode. The unstable oscillatory mode and the fast subsidence mode mainly have horizontal translation and pitch rotation, and the slow subsidence mode mainly has vertical translation. （2） Because of the existence of the unstable oscillatory mode, inclined-stroke-plane hov- ering flight is not stable. （3） Although there are large differences in stroke plane and body orientations between the in- clined-stroke-plane hovering and normal hovering, the relative position between the mean center of pressure and center of mass for these two cases is not very different, resulting in similar stability derivatives, hence similar dynamic stability properties for these two types of hovering. 展开更多
关键词 insect dynamic flight stability inclined-stroke-plane hovering natural modes of motion
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