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Modified perturbation method for eigenvalues of structure with interval parameters

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Science China(Physics,Mechanics & Astronomy) 2015年第1期58卷 75-83页

作者： WANG Chong QIU ZhiPing Institute of Solid Mechanics Beihang University

In overcoming the drawbacks of traditional interval perturbation method due to the unpredictable effect of ignoring higher order terms,a modified parameter perturbation method is presented to predict the eigenvalue intervals of the uncertain structures with interval *** the proposed method,interval variables are used to quantitatively describe all the uncertain *** order perturbations in both eigenvalues and eigenvectors are fully *** retaining higher order terms,the original dynamic eigenvalue equations are transformed into interval linear equations based on the orthogonality and regularization conditions of *** eigenvalue ranges and corresponding eigenvectors can be approximately predicted by the parameter combinatorial *** with the Monte Carlo method,two numerical examples are given to demonstrate the accuracy and efficiency of the proposed algorithm to solve both the real eigenvalue problem and complex eigenvalue problem.

关键词： interval perturbation method uncertain parameters higher order terms eigenvalue parameter combinatorial ap-proach

Stereoscopic PIV Measurements of the Flow Field in a Turbine Cascade

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Journal of Thermal Science 2017年第1期26卷 89-95页

作者： TIAN Yangtao MA Hongwei MA Rong National Key Laboratory of Science and Technology on Aero-Engines Collaborative Innovation Center of AdvancedAero-Engine School of Energy & Power Engineering Beihang University Beijing I00191 China

This paper presents experimental measurements of the flow field in a Low-speed Turbine Cascade using a stereoscopic particle-image velocimetry(SPIV). During the measurements, a pair of frame-straddling-based CCD cameras were configured at different sides of the laser light sheet, and appropriate tracing particles(DEHS) were employed. The measurements were conducted at the incidence angle of 0 degree and exit Reynolds number of 1.7 × 105 with the tip clearance 1.18% of blade chord. The tip flow features, such as the evolution and breakdown of tip leakage vortex, the horseshoe vortex, turbulence characteristics of tip leakage flow, were studied for the flow field analysis. The results showed that the tip leakage flow/vortex mainly dominate flow fields in the tip region. The tip leakage vortex performs as a concentrated vortex before its breaking down and splitting into small vortices. The highest turbulence intensity mainly occurs in the tip region along with the trajectory of tip leakage vortex, and when the vortex breaks down, the turbulence intensity reduces rapidly. Additionally, the SPIV with this configuration also shows an advantage in investigating the flow structures and mechanism inside the turbine cascade.

关键词： Stereoscopic PIV, turbine cascade, tip leakage vortex, horseshoe vortex

Equivalent method for accurate solution to linear interval equations

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Applied Mathematics and Mechanics(English Edition) 2013年第8期34卷 1031-1042页

作者：王冲邱志平 Institute of Solid Mechanics Beihang University

based on linear interval equations, an accurate interval finite element method for solving structural static problems with uncertain parameters in terms of optimization is discussed. On the premise of ensuring the consistency of solution sets, the original interval equations are equivalently transformed into some deterministic inequations. On this basis, calculating the structural displacement response with interval parameters is predigested to a number of deterministic linear optimization problems. The results are proved to be accurate to the interval governing equations. Finally, a numerical example is given to demonstrate the feasibility and efficiency of the proposed method.

关键词： linear interval equation interval finite element uncertain parameter linearoptimization

Wing kinematics measurement and aerodynamics of free-flight maneuvers in drone-flies

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Acta Mechanica Sinica 2010年第3期26卷 371-382页

作者： Yanlai Zhang Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Institute of Fluid Mechanics Beihang University 100191 Beijing China

The time courses of wing and body kinematics of two free-flying drone-flies, as they performed saccades, were measured using 3D high-speed video, and the morpho- logical parameters of the wings and body of the insects were also measured. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces and moments acting on the insects. The main results are as following. （1） The turn is mainly a 90° change of heading. It is made in about 10 wingbeats （about 55 ms）. It is of interest to note that the number of wingbeats taken to make the turn is approximately the same as and the turning time is only a little different from that of fruitflies measured recently by the same approach, even if the weight of the droneflies is more than 100 times larger than that of the fruitflies. The long axis of body is about 40° from the horizontal during the maneuver. （2） Although the body rotation is mainly about a vertical axis, a relatively large moment around the yaw axis （axis perpendicular to the long axis of body）, called as yaw moment, is mainly needed for the turn, because moment of inertial of the body about the yaw axis is much larger than that about the long axis. （3） The yaw moment is mainly pro- duced by changes in wing angles of attack： in a right turn, for example, the dronefly lets its right wing to have a rather large angle of attack in the downstroke （generally larger than 50°） and a small one in the upstroke to start the turn, and lets its left wing to do so to stop the turn, unlike the fruitflies who generate the yaw moment mainly by changes in the stroke plane and stroke amplitude.

关键词： Drone-fly - Maneuver Wing kinematicsmeasurement Aerodynamics Navier-Stokes simulation

A dimension-wise method for the static analysis of structures with interval parameters

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Science China(Physics,Mechanics & Astronomy) 2014年第10期57卷 1934-1945页

作者： XU MengHui QIU ZhiPing Institute of Solid Mechanics Beihang University

A novel method for the static analysis of structures with interval parameters under uncertain loads is proposed, which overcomes the inherent conservatism introduced by the conventional interval analysis due to ignoring the dependency phenomenon. Instead of capturing the extremum of the structural static responses in the entire space spanned by uncertain parameters, their lower and upper bounds are calculated at the minimal and maximal point vectors obtained dimension by dimension with respect to uncertain parameters based on the Legend orthogonal polynomial approximation, overcoming the potential engineering insignificance caused by the optimization strategy. After performing its theoretical analysis, both the accuracy and applicability of the proposed method are verified.

关键词： static analysis finite element method interval parameters interval analysis Legendre polynomial approximation

New robust fault-tolerant controller for self-repairing flight control systems

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Journal of Systems Engineering and Electronics 2011年第1期22卷 77-82页

作者： Zhang Ren Wei Wang Zhen Shen National Key Laboratory of Science and Technology on Holistic Control Beihang University Beijing 100191 E R. China Civil Aviation Management Institute of China Beijing 100102 P. R. China

A new robust fault-tolerant controller scheme integrating a main controller and a compensator for the self-repairing flight control system is *** main controller is designed for high performance of the original faultless *** compensating controller can be seen as a standalone loop added to the system to compensate the effects of fault guaranteeing the stability of the system.A design method is proposed using nonlinear dynamic inverse control as the main controller and nonlinear extended state observer-based *** stability of the whole closed-loop system is *** and validity of the new controller is demonstrated with an aircraft simulation example.

关键词： robust control self-repairing flight control nonlinear dynamic control extended state observer compensator.

Structural reliability analysis and reliability-based design optimization: Recent advances

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Science China(Physics,Mechanics & Astronomy) 2013年第9期56卷 1611-1618页

作者： QIU ZhiPing HUANG Ren WANG XiaoJun QI WuChao Institute of Solid Mechanics Beihang University College of Aerospace Engineering Shenyang Aerospace University

We review recent research activities on structural reliability analysis,reliability-based design optimization(RbDO) and applications in complex engineering structural *** novel uncertainty propagation methods and reliability models,which are the basis of the reliability assessment,are *** addition,recent developments on reliability evaluation and sensitivity analysis are highlighted as well as implementation strategies for RbDO.

关键词： uncertainty propagation reliability assessment reliability-based design optimization hybrid reliability

Numerical analysis of uncertain temperature field by stochastic finite difference method

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Science China(Physics,Mechanics & Astronomy) 2014年第4期57卷 698-707页

作者： WANG Chong QIU ZhiPing WU Di School of Aeronautic Science and Engineering Beihang University China Academy of Launch Vehicle Technology

based on the combination of stochastic mathematics and conventional finite difference method,a new numerical computing technique named stochastic finite difference for solving heat conduction problems with random physical parameters,initial and boundary conditions is *** with the analysis of steady-state heat conduction problems,difference discrete equations with random parameters are established,and then the computing formulas for the mean value and variance of temperature field are derived by the second-order stochastic parameter perturbation ***,the proposed random model and method are extended to the field of transient heat conduction and the new analysis theory of stability applicable to stochastic difference schemes is *** layer-by-layer recursive equations for the first two probabilistic moments of the transient temperature field at different time points are quickly obtained and easily solved by ***,by comparing the results with traditional Monte Carlo simulation,two numerical examples are given to demonstrate the feasibility and effectiveness of the presented method for solving both steady-state and transient heat conduction problems.

关键词： heat conduction uncertainty stochastic finite difference parameter perturbation stability

Effects of Measuring Positions on the Measured Aerodynamic Performance of a Centrifugal Compressor

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Journal of Thermal Science 2010年第2期19卷 110-114页

作者： Hongwei MA Jun ZHANG School of Jet Propulsion Beihang University Beijing 100191 China National Key Laboratory of Science and Technology on Aero-Engines Beijing 100191 China

This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX *** arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each *** effects of measuring positions on measurement results are *** results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point *** inlet total pressure data can be accurate when they are measured using a 3-point *** outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point *** tangential measuring positions at the outlet is effective to improve the test *** the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.

关键词： centrifugal compressor aerodynamics performance measuring error measurement position probe.