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State space discretization based methods for global analysis of nonlinear dynamic systems from model-driven to data-driven: A review
LI Zigang, HONG Ling, JIANG Jun
 doi: 10.6052/1000-0992-25-002
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Abstract:
Response behaviors of nonlinear dynamic systems are subject to their inherent global structures, such as the morphology and distribution of multi-stable attractors and basins of attraction in state space, unstable invariant sets as well as invariant manifolds. Therefore, conducting a global analysis within the specified state space can not only obtain all the information for understanding and predicting the responses, but also profoundly reveal the internal mechanisms that induce numerous dynamic phenomena, like complex bifurcations, catastrophes, or boundary transitions in the system. Currently, numerical methods remain the most effective means for the global analysis of nonlinear dynamic systems. Compared with the pointwise numerical integration or point mapping approaches, the methods based on the state space discretization, such as the cell mapping method, approximate the invariant sets by covering subsets (cells). This pattern, on the one hand, can efficiently depict the morphology of underlying global structure, and on the other hand, it characterizes the dynamics of adjacent orbits. After 40 years of development, the function of cell mapping method is continuously enhanced, the computational efficiency and accuracy are significantly improved, and its scenarios of application are also being broadened. In the second section of this review, the manners of state space discretization will be briefly classified from the perspective of current research, so that readers can understand the essence and advantages of this framework in global analysis clearly. Focusing on a series of state space discretization methods proposed in recent years, in the third section, we follow the shift in the idea of global analysis from model-driven to data-driven, introducing the latest progress achieved in two aspects: The efficient characterization of global structure and the data mining of inherent features. In the fourth section, the significance of this review is summarized, and insights will be put forward on how to further generalize the concept of global analysis within the state space discretization framework, as well as on the possible problems and expandable directions that may be faced in response to future development and application requirements.
Review on the dynamics and wave control in nonlinear periodic structures
GAO Penglin, GONG Lingyun, WANG Guoxu, LUO Yu, ZHU Junzhe, GAO Hao, MA Haibin, QU Yegao
 doi: 10.6052/1000-0992-24-047
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Abstract:
Periodic structures are an important form of constructing structures in natural and human engineering. The Bloch modulation caused by translational symmetry gives them unique band structures and rich time/frequency domain dynamic characteristics, providing new avenues for elastic/acoustic wave propagation regulation, novel wave-based functional device design, vibration and noise control, etc. Nonlinear effects can break through the constraints of linear theoretical frameworks and can enhance or even expand the functions of artificial periodic structures. However, nonlinear periodic systems have many difficulties in unit cell design and modeling analysis. They also face key scientific problems such as the broken of space-time invariance, the complexity of nonlinear response characteristics and mechanisms, which brings challenge to the dynamic design and practical application of nonlinear periodic structures. In response to the above problems, scholars have carried out some fruitful research by integrating multidisciplinary research methods in fileds such as mechanics, acoustics, materials science and band physics. This article aims to timely summarize the important research progress concerning about wave dynamics and control in nonlinear periodic structures, sort out the shortcomings and key problems, gather strength and promote the in-depth development of this field. First, the sources of nonlinear effects of periodic structures, unit cell structure design methods, and nonlinear dynamics modeling and analysis methods are summarized. Then, the main characteristics of nonlinear periodic structures in terms of passband, bandgap, and local energy confinement are reviewed, and the rich dynamic phenomena such as amplitude-induced band shift, wave mode coupling, low-frequency broadband bandgap, and spatial confinement of wave modes in the bandgap caused by nonlinearity are introduced. Some application explorations of nonlinear periodic structures in wave control devices, vibration and noise reduction are sorted out. Finally, in view of some shortcomings and key problems in existing research, several development directions that need special attention in future theoretical research and application exploration are prospected.
Recent advances on data-driven dynamics and control
DING Qian, ZHANG Shu, HUANG Rui, HE Mengxin, XU Yong, HAN Fang, LI Xiang, CUI Lanyun, WANG Qingyun, XU Jian
 doi: 10.6052/1000-0992-25-005
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Abstract:
Dynamics and control is a discipline that studies the dynamic mechanisms of systems and their control strategies, and plays an important role in modern engineering and scientific research. The complexity caused by geometric nonlinearity, the non-smoothness of contact forces, and the uncertainty of environmental interferences and multi-physics problems poses significant challenges to dynamic modeling, prediction and intelligent control. The rapid development of data-driven methods has provided new ideas and new research paradigms for addressing these challenges. Recent researches have shown that data-driven methods can not only solve some problems that traditional dynamics methods cannot address but also significantly enhance the ability to predict dynamical behavior and design advanced structures. These methods lay the foundation for intelligent research in dynamics and control and demonstrate great potential and scientific value in the modeling, analysis, and regulation and control of complex systems. This paper briefly reviews the research progress of data-driven methods in areas such as robot motion control, transonic aeroelastic modeling and analysis, dynamics design, stochastic dynamics, neurodynamics, fault diagnosis and remaining useful life prediction of machinery. It also discusses the challenges and trends in these fields.
Advances in quantum computing for fluid dynamics
MENG Zhaoyuan, LU Zhen, XIONG Shiying, ZHAO Yaomin, YANG Yue
 doi: 10.6052/1000-0992-24-041
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Abstract:
We review progress and challenges in the emerging field of quantum computing for fluid dynamics (QCFD). Quantum computing, a potentially disruptive technology, is expected to tackle pressing problems in the real world. Fluid dynamics, a complex problem in classical physics and engineering, can serve as an example to demonstrate quantum utility and advantage. Conversely, quantum computing can introduce new paradigms in fluid dynamics research. In this review, we first introduce quantum computing features, such as superposition and entanglement, and highlight the challenges of QCFD in initial state preparation, quantum state evolution, and measurement. We then focus on hybrid quantum-classical algorithms and Hamiltonian simulation for fluid dynamics, reviewing their hardware implementation on current quantum computers. In conclusion, QCFD is in its infancy, facing both challenges in quantum devices and algorithms. Although quantum computing has not yet shown an advantage in simulating strongly nonlinear fluid dynamics over classical methods, recent progress suggests its potential in enhancing simulations of complex flows, including turbulence.
Numerical simulation method and application of aircraft multi-body separation
LI Huan, CUI Pengcheng, JIA Hongyin, TANG Jing, ZHANG Jian, GONG Xiaoquan, WU Xiaojun, ZHANG Chao, ZHANG Peihong, ZHOU Naichun, ZHANG Yaobing
 doi: 10.6052/1000-0992-24-040
Abstract(601) HTML(176) PDF(313)
Abstract:
The problems of aircraft multi-body separation, such as airborne weapon delivery separation, spacecraft series/parallel stage separation, fairing separation and submunition scattering, are common in the aerospace field at present. Safe and controllable multi-body separation is an important prerequisite for aircraft to perform aerospace tasks. In recent years, with the expansion of flight boundaries and the diversification of flight missions, aircraft are facing more complex multi-body separation scenarios, so it is necessary to carry out refined multi-body separation scheme design, which puts forward higher requirements for the fidelity and fineness of multi-body separation numerical simulation. In recent years, CFD has made great progress in high-fidelity simulation of complex scenes, aiming at the extremely complex and challenging multi-body separation problem. In this paper, the latest research progress of high-fidelity numerical simulation methods and applications of aircraft multi-body separation is reviewed and prospected. Firstly, the refined simulation methods of aircraft multi-body separation are summarized, including coupled grid dynamic optimization technology, coupled separation vortex simulation method and high-precision time-marching coupling algorithm. Secondly, the coupling simulation method of aircraft multi-body separation under complex constraints/flow field/control and its application are introduced. Then, the understanding of complex mechanism of dynamic interference of aircraft multi-body separation in typical complex scenes is introduced. Finally, the existing problems and future development direction of high fidelity numerical simulation of aircraft multi-body separation are pointed out.
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