Review
Engineering, Aerospace
Jeet Panchal, Haym Benaroya
Summary: In recent decades, there has been growing interest in the field of nonlinear aeroelasticity, particularly in revisiting the control surface freeplay problem with improved computing capabilities. Modern theoretical and experimental analyses have led to various modeling approaches, but differing numerical predictions persist in the study of aeroelastic dynamical behavior and properties related to freeplay.
PROGRESS IN AEROSPACE SCIENCES
(2021)
Article
Engineering, Aerospace
Xinyu Ai, Yuguang Bai, Wei Qian, Yuhai Li, Xiangyan Chen
Summary: In this study, an experimental investigation is conducted on a scaled, all-movable horizontal tail to examine the effects of multiple free-plays on aeroelastic behaviors. The results demonstrate highly nonlinear characteristics and two independent limit cycle oscillations induced by bending and torsion free-plays. Parametric studies reveal that the free-play angles and flow velocity significantly affect the amplitude and frequency of the oscillations. The measured results provide valuable insights for predicting and preventing these oscillations in the design of all-movable horizontal tails.
Article
Engineering, Mechanical
Sai Vishal, Ashwad Raaj, Chandan Bose, J. Venkatramani, Grigorios Dimitriadis
Summary: The present study investigates the bifurcation characteristics of a pitch-plunge aeroelastic system with coupled non-smooth nonlinearities in both structural and aerodynamic aspects. The study shows that the freeplay gap plays a key role in combining the effects of structural and aerodynamic nonlinearities. Interesting discontinuity-induced bifurcation scenarios arise at high values of the freeplay gap, which can significantly impact the safety of the aeroelastic system.
NONLINEAR DYNAMICS
(2022)
Article
Engineering, Mechanical
Alexander J. Brown, Donald L. Kunz
Summary: This study investigates the factors driving limit cycle oscillations (LCO) by simulating wing flow, and finds that shock movement and trailing-edge separation may play significant roles in LCO.
JOURNAL OF FLUIDS AND STRUCTURES
(2023)
Article
Engineering, Mechanical
Guangzhong Gao, Ledong Zhu, Jiawu Li, Wanshui Han, Libo Wei, Qingchen Yan
Summary: This study investigates the post-flutter bifurcation behavior of a twin-box bridge deck and finds that the aerodynamic nonlinearities significantly affect the stability of the bridge deck. A novel wind-tunnel technique is used to measure the aerodynamic force during post-flutter oscillations, and a corresponding nonlinear model is proposed to describe the observed behavior.
JOURNAL OF FLUIDS AND STRUCTURES
(2022)
Article
Engineering, Mechanical
Hao Zhu, Yumei Hu, Wei Fan
Summary: In this paper, a piecewise-linear nonlinear dynamic model is proposed to study the nonlinear dynamics of an all-movable rudder system with freeplay nonlinearity. The time histories, phase portrait, and Poincare section graph of the rudder system are calculated using the seam method. The evolution of different motion modes with varying structural parameters and the influences of various parameters are discussed. This study can provide guidance for ground vibration tests and modal parameter identification of the rudder system.
IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY-TRANSACTIONS OF MECHANICAL ENGINEERING
(2023)
Article
Engineering, Mechanical
Renan F. Correa, Flavio D. Marques
Summary: This paper investigates the nonlinear dynamics of a typical airfoil section mounted on a bistable spring support during plunging motion, and analyzes the system's response for a set of geometrical configurations. The study shows that the bistable effect can be advantageous in energy extraction problems in aeroelastic systems, while the hardening effect in pitching motion reduces limit cycle oscillation amplitudes and delays snap-through occurrences.
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
(2021)
Article
Engineering, Aerospace
Madhusudan A. Padmanabhan, Earl H. Dowell
Summary: This work explores the similar dynamic behavior of landing gears and all-movable control surfaces, which both exhibit shimmy/flutter limit cycle oscillations due to stiffness and damping nonlinearities. The authors extend their computational methods to systems with multiple nonlinearities and focus on the physical insights obtained. The results reveal the contribution of specific nonlinearities to the landing gear response and the shaping and modification of the flutter response in all-movable surfaces. The findings also provide a reinterpretation of wind tunnel flutter tests for all-movable horizontal tails.
JOURNAL OF AIRCRAFT
(2023)
Review
Neurosciences
Lingyun (Ivy) Xiong, Alan Garfinkel
Summary: This article argues that oscillations play critical physiological roles in avoiding desensitization, maintaining balanced chemical levels, increasing resistance to noise, reconciling incompatible conditions, and synchronizing small units into one large effect. It also emphasizes the importance of a dynamic approach and nonlinear dynamics in understanding and studying oscillatory processes in various levels of biological systems.
JOURNAL OF PHYSIOLOGY-LONDON
(2023)
Article
Acoustics
Peihan Wang, Zhigang Wu, Chao Yang
Summary: The frequency-time domain method is a powerful tool but limited to steady-state solutions. A modified frequency-time domain method is proposed to investigate nonlinear dynamic behaviors with initial conditions. The feasibility is validated through numerical results and compared with the Runge-Kutta algorithm. The sensitivity of parameters and calculation methods of convolution integral contributes to strategies for accuracy.
JOURNAL OF SOUND AND VIBRATION
(2023)
Article
Engineering, Mechanical
B. E. Saunders, R. Vasconcellos, R. J. Kuether, A. Abdelkefi
Summary: This study investigates five different continuous representations to accurately capture nonlinear behaviors in dynamic systems, aiming to determine their applicability limits and potential numerical issues.
NONLINEAR DYNAMICS
(2022)
Article
Acoustics
Hao Zhou, Gang Wang, QuanZheng Li, Yi Liu
Summary: The nonlinear flutter characteristics of a two-dimensional elastic panel subjected to an impinging inviscid oblique shockwave are investigated, considering factors such as shock impingement location, cavity pressure, and initial perturbation. Two computational methods are used for fluid-structure interaction simulations, revealing new findings regarding the effects of shock impingement location and cavity pressure on system bifurcation type and the existence of multiple stable limit cycle oscillations due to the coupling of higher-order modes. The presence of these limit cycle oscillations suggests a higher risk of structural fatigue failure.
JOURNAL OF SOUND AND VIBRATION
(2023)
Article
Engineering, Mechanical
Mehmet Selim Akay, Alexander D. Shaw, Michael I. Friswell
Summary: Nonlinearities in rotating systems lead to various rich phenomena, and numerical continuation is used in this study to explore the responses of such systems systematically. Asynchronous responses with oscillating amplitude are observed at certain drive speeds due to internal resonance, isolated from more trivial synchronous responses. This work demonstrates the potential of numerical continuation as a tool to systematically explore the responses of nonlinear rotor systems.
NONLINEAR DYNAMICS
(2021)
Article
Acoustics
Xinyu Ai, Yuguang Bai, Wei Qian, Yuhai Li, Xiangyan Chen
Summary: This paper develops the describing function (DF) method to investigate the complex dynamic response of all-movable horizontal tail with free-play. The developed DF method provides piecewise expressions for the limit cycle oscillation (LCO) and predicts high-order harmonics. Experimental results show good agreement with numerical calculations, indicating the effectiveness of the proposed method. The influence of initial parameters on LCO characteristics is analyzed.
JOURNAL OF LOW FREQUENCY NOISE VIBRATION AND ACTIVE CONTROL
(2023)
Article
Construction & Building Technology
Guangzhong Gao, Ledong Zhu, Hua Bai, Wanshui Han, Feng Wang
Summary: This study explores the modeling of nonlinear aerodynamic forces in aeroelastic instabilities, highlighting the equivalent nature of Van der Pol-type and Rayleigh-type models in amplitude-dependent aerodynamic damping. An identification algorithm for aerodynamic parameters is proposed to enhance parameter robustness and ensure model equivalence. Wind-tunnel tests show that both model types are suitable for predicting vibration amplitudes of nonlinear aeroelastic instabilities, with differences in higher-order harmonic responses.
ADVANCES IN STRUCTURAL ENGINEERING
(2021)
Article
Chemistry, Multidisciplinary
Sun Yukai, Yang Chao, Wu Zhigang, Bai Liuyue
APPLIED SCIENCES-BASEL
(2020)
Article
Engineering, Aerospace
Yitao Zhou, Zhigang Wu, Chao Yang
Summary: Feedforward gust alleviation control using gusts as input signals has attracted increasing attention. The study derives a calculation method for obtaining high-quality gust information during aircraft flight and establishes a simplified calculation method. Wind tunnel tests verify the gust calculation method. Numerical simulations investigate the influence of sensor characteristics on gust calculation accuracy and alleviation performance. Experimental results show a 39.12% reduction in wing root bending moment and a 65.47% reduction in wingtip acceleration on average.
Article
Engineering, Aerospace
Changkun Yu, Zhigang Wu, Chao Yang
Summary: With the increasing bandwidths of servo control systems and decreasing mode frequencies, aeroservoelastic (ASE) stability evaluation has become an essential part of flight vehicle design. However, traditional methods are limited by modeling errors and complex designs. This paper proposes a novel ASE stability evaluation method based on the ground frequency response test (FRT), which can accurately evaluate ASE stability under different conditions.
Article
Engineering, Aerospace
Zexuan Yang, Chao Yang, Jiamin Zhao, Zhigang Wu
Summary: This study uses a fluid-structure coupling method to calculate the response of a falling rocket fairing. Vibration divergence of the fairing is observed and analyzed, and a framework for fluid-structure coupling-based analysis is proposed. The mechanism of the fairing and the effects of various factors are discussed, and dangerous and safe regions are identified. Methods to prevent damage to the fairing are provided.
Article
Engineering, Aerospace
Yitao Zhou, Zhigang Wu, Chao Yang
Summary: This paper designs and analyzes a combined control system composed of feedforward control system and feedback control system for improving aircraft ride quality and reducing gust load. The simulation and experimental results show that the combined control system has better gust alleviation performance for various gust excitations.