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Series expansion feasibility of singular integral in method of moments

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Journal of Systems engineering and Electronics 2014年第3期25卷 386-392页

作者： Jinzu Ji Peilin Huang school of aeronautic science and engineering Beihang University

When calculating electromagnetic scattering using method of moments （MoM）, integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour integral. The integrand is expanded to Taylor series and the integral results in a closed form. The cut-off error is analyzed to show that the series converges fast and only about 2 terms can agree wel with the accurate result. The comparison of the perfect electric conductive （PEC） sphere＇s bi-static radar cross section （RCS） using MoM and the accurate method validates the feasibility in manipulating the singularity. The error due to the facet size and the cut-off terms of the series are analyzed in examples.

关键词： method of moments (MoM) singular term series cut-off error radar cross section (RCS).

Crashworthiness uncertainty analysis of typical civil aircraft based on Box–Behnken method

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Chinese Journal of aeronautics 2014年第3期27卷 550-557页

作者： Ren Yiru Xiang Jinwu school of aeronautic science and engineering Beihang University

The crashworthiness is an important design factor of civil aircraft related with the safety of occupant during impact accident. It is a highly nonlinear transient dynamic problem and may be greatly influenced by the uncertainty factors. Crashworthiness uncertainty analysis is conducted to investigate the effects of initial conditions, structural dimensions and material properties. Simplified finite element model is built based on the geometrical model and basic physics phenomenon. Box-Behnken sampling and response surface methods are adopted to obtain gradient information. Results show that the proposed methods are effective for crashworthiness uncertainty analysis. Yield stress, frame thickness, impact velocity and angle have great influence on the failure behavior, and yield stress and frame thickness dominate the uncertainty of internal energy. Failure strain and tangent modulus have the smallest influence on the initial peak acceleration, and gradients of mean acceleration increase because the appearance of material plastic deformation and element failure.

关键词： Box-Behnken method Civil aircraft Crashworthiness Failure behavior Uncertainty analysis

Multi-parameter decoupling and slope tracking control strategy of a large-scale high altitude environment simulation test cabin

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Chinese Journal of aeronautics 2014年第6期27卷 1390-1400页

作者： Li Ke Liu Wangkai Wang Jun Huang Yong Liu Meng school of aeronautic science and engineering Beihang University

A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.

关键词： Decoupling control Environment cabin Fuzzy control Liquid nitrogen Mathematical model Vacuum

Numerical simulation of ice accretion in supercooled large droplet conditions

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science China(Technological sciences) 2019年第7期62卷 1191-1201页

作者： CAO Yi Hua XIN Miao school of aeronautic science and engineering Beihang University

The simulated methods for ice accretion on two-dimensional airfoil surface are established completely under the Eulerian framework in supercooled large droplet(SLD) conditions. The two-dimensional code to solve the partial differential equations(PDEs) of droplet phase is derived to simulate the impingement characteristic of SLD. Also, several semi-empirical models which explain the droplet-wall interaction are compared and discussed to show respective features when simulating the splashing phenomenon. In particular, a new boundary condition for wall called penetrable wall for splashing droplet(PWSD) is proposed to deal with the impingement of SLD on solid surface, which efficiently improves the accuracy of simulation. Then the improved impingement characteristic of SLD is input into the extended mass and heat transfer model to simulate the ice growth on airfoil surface. The multistep advanced method is carried out to better match the physical phenomenon of ice growth. At last, the simulated results of critical parameters: local droplet collection efficiency and the height of ice growth are compared with the experimental data which verify the applicability of proposed models.

关键词： numerical simulation supercooled large droplet ice accretion penetrable wall for splashing droplet

Epistemic uncertainty quantification in flutter analysis using evidence theory

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Chinese Journal of aeronautics 2015年第1期28卷 164-171页

作者： Tang Jian Wu Zhigang Yang Chao school of aeronautic science and engineering Beihang University

Aimed at evaluating the structural stability and flutter risk of the system, this paper manages to quantify epistemic uncertainty in flutter analysis using evidence theory, including both parametric uncertainty and method selection uncertainty, on the basis of information from limited experimental data of uncertain parameters. Two uncertain variables of the actuator coupling system with unknown probability distributions, that is bending and torsional stiffness, which are both described with multiple intervals and the basic belief assignment（BBA） extricated from the modal test of actuator coupling systems, are taken into account. Considering the difference in dealing with experimental data by different persons and the reliability of various information sources, a new combination rule of evidence––the generalized lower triangular matrices method is formed to acquire the combined BBA. Finally the parametric uncertainty and the epistemic uncertainty of flutter analysis method selection are considered in the same system to realize quantification. A typical rudder of missile is selected to examine the present method, and the dangerous range of velocity as well as relevant belief and plausibility functions is obtained. The results suggest that the present method is effective in obtaining the lower and upper bounds of flutter probability and assessing flutter risk of structures with limited experimental data of uncertain parameters and the belief of different methods.

关键词： uncertainty belief actuator triangular matrices missile assignment dealing parametric quantification

An experimental analysis of situation awareness for cockpit display interface evaluation based on flight simulation

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Chinese Journal of aeronautics 2013年第4期26卷 884-889页

作者： Wei Hengyang Zhuang Damin Wanyan Xiaoru Wang Qun school of aeronautic science and engineering Beihang University

Aircraft cockpit display interface （CDI） is one of the most important human-machine interfaces for information perceiving. During the process of aircraft design, situation awareness （SA） is frequently considered to improve the design, as the CDI must provide enough SA for the pilot to maintain the flight safety. In order to study the SA in the pilot-aircraft system, a cockpit flight simulation environment is built up, which includes a virtual instrument panel, a flight visual display and the corresponding control system. Based on the simulation environment, a human-in-the-loop experiment is designed to measure the SA by the situation awareness global assessment technique （SAGAT）. Through the experiment, the SA degrees and heart rate （HR） data of the subjects are obtained, and the SA levels under different CDI designs are analyzed. The results show that analyzing the SA can serve as an objective way to evaluate the design of CDI, which could be proved from the consistent HR data. With this method, evaluations of the CDI design are performed in the experimental flight simulation environment, and optimizations could be guided through the analysis.

关键词： Cockpit display interface Design evaluation Flight simulation Heart rate SAGAT Situation awareness

Experimental investigation on impact performances of GLARE laminates

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Chinese Journal of aeronautics 2015年第6期28卷 1784-1792页

作者： Chen Qi Guan Zhidong Li Zengshan Ji Zhaojie Zhuo Yue school of aeronautic science and engineering Beihang University

An experimental investigation was carried out on the damage resistance to a concen- trated quasi-static indentation force and low-velocity impact of four kinds of glass-reinforced aluminum laminates （GLARE for short）. Compared with the experimental results of the CFRP （Carbon Fiber Reinforced Plastics） laminates, the performance of GLARE was determined. By means of concentrated quasi-static indentation force test, typical force displacement response, the maximum contact force and dent depth were received, Through drop-weight low-velocity impact tests, impact force histories, indentation depths （through a new method） and dissipated energy were obtained. The test results show that the force-displacement response of GLARE 4 laminates under the concentrated quasi-static indentation force has an obvious fiat roof and the failure is instantaneous, which are different from CFRP laminates. The indention will be visible once the impact happens. C-scan results find that there is no delamination besides the impact area after both the concentrated quasi-static indentation and low-velocity impact. The dissipated energy approximately equals the impact energy.

关键词： Concentrated quasi-staticindentation force Delamination GLARE laminate Impact Indentation

Dynamic stiffness testing-based flutter analysis of a fin with an actuator

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Chinese Journal of aeronautics 2015年第5期28卷 1400-1407页

作者： Zhang Renjia Wu Zhigang Yang Chao school of aeronautic science and engineering Beihang University

engineering-oriented modeling and synthesized modeling of the fin-actuator system of a missile fin are introduced, including mathematical modeling of the fin, motor and multi-stage gear reducer. The fin-actuator model is verified using dynamic stiffness testing. Good agreement is achieved between the test and theoretical results. The parameter-variable analysis indicates that the inertia of the motor rotor, reduction ratio of the reducer, connection stiffness and damping between the actuator and fin shaft have significant impacts on the dynamic stiffness characteristics. In flutter analysis, test data are directly used in the frequency domain method and indirectly used in the time domain method through the updated fin-actuator model. The two methods play different roles in engineering applications but are of equal importance. The results indicate that dynamic stiffness and constant stiffness treatments may lead to completely different flutter characteristics. Attention should be paid to the design of the fin-actuator system of a missile.

关键词： Actuator Aeroelasticity Dynamic stiffness Flutter Ground vibration test Structural dynamics

Comparative assessment of SAS and DES turbulence modeling for massively separated flows

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Acta Mechanica Sinica 2016年第1期32卷 12-21页

作者： Weilin Zheng Chao Yan Hongkang Liu Dahai Luo school of aeronautic science and engineering Beihang University

Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation （SAS） and detached eddy simu- lation （DES）, in comparison with the existing experimental data. The new version of the model developed by Egorov and Menter is assessed, and advantages and disadvantages of the SAS simulation are analyzed in detail to provide guidance for industrial application in the future. Moreover, the mechanism of the scale-adaptive characteristics in separated regions is discussed, which is obscure in previous analyses. It is con- cluded that： the mean flow properties satisfactorily agree with the experimental results for the SAS simulation, although the prediction of the second order turbulent statistics in the near wake region is just reasonable. The SAS model can produce a larger magnitude of the turbulent kinetic energy in the recir- culation bubble, and, consequently, a smaller recirculation region and a more rapid recovery of the mean velocity out- side the recirculation region than the DES approach with the same grid resolution. The vortex shedding is slightly less irregular with the SAS model than with the DES approach, probably due to the higher dissipation of the SAS simulation under the condition of the coarse mesh.

关键词： Scale-adaptivelength scale Bluff bodies simulation von Karman Massively separated flows Computational fluid dynamics