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2021 Vol. 51, No. 3

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50 years of service to the community of mechanics helped young scholars grow

2021, 51(3): 427-427. doi: 10.6052/1000-0992-21-049

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Special Issue for 50th Anniversary

Nonlinear aeroservoelasticity of aircraft

HUANG Rui, HU Haiyan

2021, 51(3): 428-466. doi: 10.6052/1000-0992-21-010

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Advanced flight vehicles have been requiring lightweight structures and the expansion of bandwidth and authority of control systems. Hence, the coupled dynamics of the unsteady aerodynamics, the flexible aircraft structure, and the active control system have been an important research field in dynamics and control. The community of aeronautical technology has paid much attention to the aeroelastic stability and active control of aircraft since the 1980s, but has made less effort to study the effects of the aerodynamic and structural nonlinearities, as well as time delays in a control loop, on the aeroservoelastic behaviors of aircraft. The studies of these effects need to model the high-dimensional and parametric-varying dynamic systems with strong aerodynamic/structural nonlinearity, and hence, face with the coupling among unsteady aerodynamics, aircraft structure, and active control system. The cutting-edge problems include how to develop nonlinear aeroservoelastic modeling theory, how to reveal the dynamic mechanism behind the induced aeroelastic vibrations and how to carry out wind tunnel tests for aeroservoelasticity. This review article surveys the recent advances in reduced modeling of unsteady aerodynamics, nonlinear structural dynamics, design of aeroservoelastic control law, and experimental studies on aeroservoelastic systems, with an emphasis on the researches of the authors’ team in nonlinear aeroservoelasticity. The article also makes a number of suggestions for studies in the future.

Advances in complex low speed flow around a prolate spheroid

CONG Chenghua, DENG Xiaogang, MAO Meiliang

2021, 51(3): 467-619. doi: 10.6052/1000-0992-20-036

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Understanding and predicting the flow around the prolate spheroid is of great engineering significance to guide the design of vehicles such as aircraft and submarines. In recent years, a lot of experimental and numerical studies have been carried out on the flow around the prolate spheroid. The qualitative description and quantitative research of flow separation around prolate spheroid at attack angle are presented, promoting the identification and topology research of three-dimensional separation. The experimental results of oil flow, smoke, dye, hydrogen bubble, and LDV are given. The flow field characteristics are analyzed, and the existing problems are pointed out. Based on the introduction of the above phenomena, the effects of separation on aerodynamic force, noise, and wake are introduced. The effects of test conditions such as transition zone, protrusion, depression, and tail support on flow are also discussed. There are obvious differences between the above steady flow and the unsteady maneuvering process. The unsteady maneuvering process can not be treated as a steady or quasi-steady problem. During the maneuvering process, the separation will be delayed obviously, and the aerodynamic force will also change obviously. The greater the angle of attack, the higher the maneuvering rate, the more noticeable this effect will be. At present, RANS turbulence model is still the primary engineering method to solve the large-scale separated flow around the prolate spheroid. However, LES, DES, and other methods have gradually been widely used. Due to the limitation of computer capability, DNS can only be used in the case of lower Reynolds number but not in high Reynolds number flow. The difference between the numerical simulation and the unsteady simulation is more significant. Finally, the research progress of prolate spheroid transition is introduced. The mechanism and identification of TS transition and cross-flow transition are more accurate. The numerical simulation results are basically consistent with the experimental results, but the understanding of reattachment transition is not clear enough, especially on the windward side. Therefore, the research of prolate spheroid transition still needs to rely on experiments.

Some research advances in downhole tubular mechanics and control methods

GAO Deli, HUANG Wenjun

2021, 51(3): 620-647. doi: 10.6052/1000-0992-21-028

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Research on down-hole tubular mechanics has been more than 70 years so far. Many breakthrough research results have been obtained, and they have been successfully applied in drilling & completion engineering. However, due to the complexity of wellbore constraints and operating conditions, it has not been able to fully and accurately reveal the complicated mechanical behaviors of tubular strings in long and narrow wellbores. These facts also make the current design and control methods difficult to solve many complex engineering problems. First, this article reviews the overall development context of down-hole tubular mechanics and introduces the static deformation control equations of down-hole tubular strings. Next, research progress, the latest results and the existing problems of several important tubular mechanical problems are introduced, including down-hole tubular buckling, down-hole tubular friction and wear, safe operation limit of down-hole tubular strings, mechanics of bottom hole assembly and the corresponding design & control methods. Last, a summary and outlook on down-hole tubular mechanics are made. It is expected to provide some meaningful enlightenment for the development of down-hole tubular mechanics and control methods and the improvement of drilling & completion engineering technology.

Fundamental mechanics problems in metal additive manufacturing: A state-of-art review

LIAN Yanping, WANG Panding, GAO Jie, LIU Jikai, LI Quhao, LIU Changmeng, HE Xiaofan, GAO Liang, LI Hao, LEI Hongshuai, LI Huimin, XIAO Dengbao, GUO Xu, FANG Daining

2021, 51(3): 648-701. doi: 10.6052/1000-0992-21-037

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Metal additive manufacturing (AM) is a kind of disruptive manufacturing technology that considers the needs of complex geometry fabrication and high-performance part fabrication. Hence, it has broad applications and extensive development space in aviation, aerospace, transportation, nuclear power, to name a few. However, its large-scale applications suffer from the challenge, including improving manufacturing efficiency and achieving the geometry and mechanical property as desired, which is a cross-cutting problem involving multi-discipline such as mechanics, optics, material science, mechanical engineering, control science. In the viewpoint of mechanics associated with the challenge, this paper critically reviews the recent research progress of AM-oriented structure topology optimization design, numerical simulation of the metal AM process, as-built defects characterization, and mechanical performance evaluation of the fabricated metal materials and components, which are referred to as structure design-process modelling-performance evaluation for metal AM. Finally, research topics that are required to address the fundamental mechanical problems in terms of structure design-process modelling-performance evaluation in AM of metallic components are provided.

Research on deep shaft hoisting dynamics

HE Manchao

2021, 51(3): 702-728. doi: 10.6052/1000-0992-21-032

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With the increasing depletion of shallow coal resources, China’s coal mining is developing in the direction of deepening and large-scale development. The annual production capacity of newly built and expanded large vertical shafts has reached 10 million tons, and the maximum mining depth has reached 1 500 m. During the hoisting process of kilometer deep well, the vibration of hoisting wire rope and container is caused, especially the large swing of free-hanging balance rope, which seriously affects the development of multi rope friction hoisting system to high speed and depth. Supported by the key special project “the basic theory and key technology of deep coal mine construction and upgrading” within the national key research and development plan “Deep Ground Resources Exploration and Mining,” the dynamic model of free-hanging balance rope hoisting system with adaptive grid number is established. The mechanism of large swing of balance rope induced by traditional hoisting system is revealed. A new deep shaft SAP hoisting mode is proposed. The SAP hoisting system dynamic model and non-smooth dynamics model are constructed, and the non-smooth dynamic characteristics and nonlinear vibration evolution law of the system under the influence of multiple parameters are revealed. Developed SAP hoisting technology and equipment suitable for deep hoisting and carried out on-site research on SAP hoisting technology and equipment. It solves the key problems of large swing of balance rope and large vibration of hoisting container during the operation of the vertical shaft hoisting system of Daqiang Coal Mine. The safety of the high-speed operation of the hoisting system is improved, and the problem that the large swing of the balance rope is difficult to control is eliminated.

2021 Vol. 51, No. 3

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