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Study of control effects of vortex generators on a supercritical wing

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Science china(Technological Sciences) 2010年第8期53卷 2038-2048页

作者： HUANG JingBo 1 ,XIAO ZhiXiang 1 ,FU Song 1 &ZHANG Miao 2 1 School of aerospace engineering,Tsinghua University,Beijing 100084,china 2.shanghai Aircraft Design and Research institute of COMAC,shanghai 200232,china 1. School of aerospace engineering Tsinghua University Beijing 100084 China2. Shanghai Aircraft Design and Research Institute of COMAC Shanghai 200232 China

Flows around vortex generators(VGs),which serve as one of the important flow control methods,are investigated by solving Reynolds-averaged Navier-Stokes(RANS)*** influences on the main flow of VGs are intended to ***, the flow around a single VG on a flat plane is computed to validate the schemes and to acquire basic knowledge of this kind of ***,transonic flow past a standard model,named by ONERA-M6 wing,is predicted to investigate the flow features of shockwave/boundary-layer interactions(SWBLI).Thirdly,the effects of a row of VGs mounted about 25%local chord on a supercritical wing are analyzed in transonic condition with strong ***,VGs are mounted more upwind(about 3.5%local chord)to explore the effects at low speed and high incidence *** numerical results show that seven VGs can effectively suppress the separations behind the strong SWBLI and decrease spanwise flow and wing-tip vortex in transonic *** also can decrease the large scope of separation over the wing at low speed with high angle of attack.

关键词： supercritical wing vortex generator(VG) shockwave/boundary-layer interactions(SWBLI)

Time-varying sliding mode control for a class of uncertain MIMO nonlinear system subject to control input constraint

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Science china(Information Sciences) 2010年第1期53卷 89-100页

作者： JIN YongQiang1,2, LIU XiangDong1, QIU Wei2 & HOU ChaoZhen1 1Department of Automatic control, Beijing institute of Technology, Beijing 100081, china 2aerospace System engineering shanghai, shanghai 201108, china 1. Department of Automatic control Beijing Institute of Technology Beijing 100081 China2. Aerospace System Engineering Shanghai Shanghai 201108 China

To solve the regulator problem of a class of uncertain MIMO nonlinear systems subject to control input constraint, three types of time-varying sliding mode control laws are proposed. The sliding surfaces pass the initial value of the system at the initial time, and are shifted/rotated towards the predetermined ones. The controller parameters are optimized by genetic algorithm (GA). Lyapunov method is adopted to prove the stability and robustness to the parameter uncertainties and external disturbance. By mean of time-varying sliding mode control law, the reaching phase in the conventional sliding mode control is eliminated, and the system is guaranteed to have robustness from the very beginning. Taking the control of two-link manipulator and attitude tracking of rigid spacecraft as two examples, we illustrate the features of the time-varying sliding mode control. The simulation results show the validity of the control law to a class of uncertain MIMO systems. Better robustness against the uncertainties and external disturbance could be achieved by time-varying sliding mode control without violating the constraint on control input.

关键词： time-varying sliding surface sliding mode control MIMO nonlinear system uncertain control input constraints

Nonlinear constitutive law for ferroelectric/ferroelastic material and its finite element realization

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Science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 70-86页

作者： LI YaoChen Department of aerospace engineering and Applied Mechanics,Tongji University,shanghai 200092,china Department of aerospace engineering and Applied Mechanics Tongji UniversityShanghai 200092 China

The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.

关键词： ferroelectric/ferroelastic material constitutive law nonlinear finite element method.

Fold-Hopf bifurcation in a simplified four-neuron BAM (bidirectional associative memory) neural network with two delays

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Science china(Technological Sciences) 2010年第3期53卷 633-644页

作者： GE JuHong & XU Jian School of aerospace engineering and Applied Mechanics,Tongji University,shanghai 200092,china 1. School of aerospace engineering and Applied Mechanics Tongji University Shanghai 200092 China

The bidirectional associative memory (BAM) neural network with four neurons and two delays is considered in the present paper.A linear stability analysis for the trivial equilibrium is firstly employed to provide a possible critical point at which a zero and a pair of pure imaginary eigenvalues occur in the corresponding characteristic equation.A fold-Hopf bifurcation is proved to happen at this critical point by the nonlinear *** coupling strength and the delay are considered as bifurcation parameters to investigate the dynamical behaviors derived from the fold-Hopf *** dynamical behaviours are qualitatively classified in the neighbourhood of the fold-Hopf bifurcation point by using the center manifold reduction (CMR) together with the normal *** bifurcating periodic solutions are expressed analytically in an approximate *** validity of the results is shown by their consistency with the numerical simulation.

关键词： codimension-two bifurcation time delay solution classification unfolding centre manifold

Optimal motion planning of an underactuated spacecraft using wavelet approximate method

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Progress in Natural Science:Materials International 2006年第8期16卷 868-873页

作者： GE Xinsheng, CHEN Liqun and LIU Yanzhu (Beijing institute of Machinery, Beijing 100085, china Department of Mechanics, shanghai University, shanghai 200072, china Department of engineering Mechanics, shanghai Jiaotong University, shanghai 200030, china) [a]Beijing institute of Machiner Beijing China [b]Department of Mechanics Shanghai University Shanghai China [c]Department of engineering Mechanics Shanghai Jiaotong University Shanghai China

An optimal motion planning scheme using wavelet approximation is proposed for an underactuated spacecraft. The motion planning of an underactuated spacecraft can be formulated as an optimal control of a drift-free system. A cost functional is used to incorporate the control energy and the final state errors. The motion planning is to determine control inputs to minimize the cost functional. Using the method of wavelet, one can transform an infinite-dimensional optimal control problem to a finite-dimensional one and use Gauss-Newton algorithm to solve it for a feasible trajectory which satisfies nonholonomic constraints. The proposed scheme has been applied to a rigid spacecraft with two momentum wheels. The numerical simulation results indicate that optimal control with wavelet approximation is an effective approach to steering an underactuated spacecraft system from the initial configuration to the final configuration.

关键词： underactuated spacecraft motion planning optimal control nonholonomic constraint wavelet analysis.

WATER TUNNEL EXPERIMENTAL INVESTIGATION ON THE DRAG REDUCTION CHARACTERISTICS OF THE TRAVELING WAVY WALL

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Journal of Hydrodynamics 2011年第1期23卷 65-70页

作者： YAO Yan LU Chuan-jing SI Ting ZHU Kun Department of engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China Beijing Electromechanic engineering institute Beijing 100074 China State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Shanghai 200030 China Department of modem Mechanics University of Science and Technology of China Hefei 230027 China

Drag reduction experiment of the traveling wavy wall at high Reynolds number is conducted.A suit of traveling wavy wall device is *** drag forces of the traveling wavy wall with various wave speeds（c）are measured under different water speeds（U）in the K15 cavitation water tunnel and are compared with that of the flat *** results show that the mean drag force of the traveling wavy wall have decreased and then increased with oscillation frequency increasing at the same flow *** different flow speeds,when traveling wave wall reached to the minimum of drag force,the corresponding the ratio of the wall motion phase speed c to flow speed U,c /U is slightly *** the parameters of the experiment,whenc /U reaches a certain value,the drag force of the traveling wavy wall can be less than that of the flat *** drag reduction can be up to 42%.Furthermore,as the value ofc /U increases,the traveling wavy wall can restrain the separation and improve the quality of flow field.

关键词： flow control drag reduction traveling wavy wall water tunnel test

Impact chaos control and stress release——A key for development of ultra fine vibration milling

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Progress in Natural Science:Materials International 2002年第5期12卷 18-23页

作者： WANG Shulin(Department of Power engineering, University of shanghai for Science and Technology, shanghai 200093, china) shanghai Univ Sci & Technol Dept Power Engn Shanghai 200093 Peoples R China

Through our previous experimental and analytical studies, it has been discovered that the key for the development of vibration milling is the impact chaos control and stress release. The necessities for the chaos control and stress release are: (i) to strictly e-liminate the sub-harmonics; (ii) to control the super-harmonics to a lower level and (iii) to load the system compressively with relatively higher period, in order that the vibration energy can be absorbed by the particles effectively and sufficiently. A new vibration model for ultra fine milling is proposed, which has wide applications in preparing ultra fine particles.

关键词： vibration mills ultra fine milling impact chaos control stress release.

Fracture analysis of a functionally graded interfacial zone between two dissimilar homogeneous materials

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Science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 540-552页

作者： CHENG Zhanqi1,2 & ZHONG Zheng1 1. School of aerospace engineering and Applied mechanics, Tongji University, shanghai 200092, china 2. College of Civil engineering, Zhengzhou University, Zhengzhou 450002, china 1. School of aerospace engineering and Applied mechanics Tongji University Shanghai 200092 China 2. College of Civil engineering Zhengzhou University Zhengzhou 450002 China

In this paper the plane elasticity problem for a functionally graded interfacial zone containing a crack between two dissimilar homogeneous materials has been considered. It is assumed that in the interfacial zone the reciprocal of the shear modulus is a linear function of the coordinate, while Possion’s ratio keeps constant. By utilizing the Fourier transformation technique and the transfer matrix method, the mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. The influences of the geometric parameters and the graded parameter on the stress intensity factors are investigated. The numerical results show that the graded parameters, the thickness of interfacial zone, the crack size and location have significant effects on the stress intensity factors.

关键词： functionally graded material interfacial zone fracture stress intensity factor

EXPERIMENTAL INVESTIGATION ON THE DRAG REDUCTION CHARACTERISTICS OF TRAVELING WAVY WALL AT HIGH REYNOLDS NUMBER IN WIND TUNNEL

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Journal of Hydrodynamics 2010年第5期22卷 719-724页

作者： YAO Yan LU Chuan-jing SI Ting ZHU Kun Department of engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China Beijing Electromechanic engineering institute Beijing 100074 China State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Shanghai 200030 China Department of Modern Mechanics University of Science and Technology of China Hefei 230027 China

Drag reduction experiments of the traveling wavy wall at high Reynolds number, ranging from 1.46×106 to 5.83×106 based on the free-stream velocity and the model length, were conducted. A suit of traveling wavy wall device was developed and its characteristics of drag reduction at high Reynolds number were investigated. The drag forces of the traveling wavy wall with various wave speeds （ c ） were measured at different wind speeds （U ） in the FL-8 low-speed wind tunnel and compared with the drag force of the flat plate. The results show that the mean drag force of the traveling wavy wall decreases as the value of c /U increases, at different wind velocities, the values of c /U corresponding to minimal drag force of the traveling wavy wall are different, when the values of c /U are larger than 0.6, the mean drag forces of the traveling wavy wall are smaller than those of the flat plate, and the drag reduction can be up to 60%. The drag reduction effectiveness of traveling wavy wall is thus achieved. Furthermore, as the value of c /U increases, the traveling wavy wall can restrain the separation and improve the quality of flow field.

关键词： flow control drag reduction traveling wavy wall wind tunnel test