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A new semiactive levertype tuned mass damper (TMD) with an adjustable frequency is proposed to control vertical bending buffeting and torsional buffeting and flutter in the whole velocity range of bridge decks.


The wind excitations of the system are the buffeting and selfexcited forces simulated in time domain using measured aerodynamic coefficients and flutter derivatives.


Flutter control effect and mechanism of centralslotting for longspan bridges


If the original section is inappropriate or the slot width is unsuitable, centralslotting will even deteriorate the structural flutter performance.


In an investigation of the flutter of turbines it is necessary to know what is the influence on the unsteady aerodynamic characteristics of a cascade of oscillating profiles of the interaction of cascades in a turbine.

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Thus it is necessary to conduct a transonic flutter test to evaluate this configuration quantitatively.


The second transonic flutter test was conducted using the wing with the overthewing engine nacelle.


The subscale wing encountered flutter within the testing envelope of the wind tunnel during the flutter test.


The Hopf bifurcations of an airfoil flutter system with a cubic nonlinearity are investigated, with the flow speed as the bifurcation parameter.




 In this papr, the typical block diagram of the active flutter suppression system of aircraft has been presented.The frequency response method (modified Nyquist method)has been described in detail, and the corrected network control law and local aeroelastic dampig control law have been demonstrated. At the same time, the substantiating test techniques have been described,especially the analog simulation test technique, subcritical flutter test, closedloop test, etc. This paper provides a method for studying... In this papr, the typical block diagram of the active flutter suppression system of aircraft has been presented.The frequency response method (modified Nyquist method)has been described in detail, and the corrected network control law and local aeroelastic dampig control law have been demonstrated. At the same time, the substantiating test techniques have been described,especially the analog simulation test technique, subcritical flutter test, closedloop test, etc. This paper provides a method for studying the active flutter suppression system.  本文给出了颤振主动抑制系统的典型框图,详细地叙述了频率响应法(修改的乃奎斯特法),讨论了校正网络控制律和局部阻尼控制律。同时,还介绍了几种试验验证技术,主要是模拟仿真试验技术、亚临界颤振试验、闭环系统试验等。这些内容提供了研究颤振主动抑制系统的一种方法。  HAJIFII is a program system developed by Chinese Aeronautical Establishment(CAE). It is able to accomplish the calculation of the modal characteristics of aircraft structures as well as the flutter and gust response analysis with the active control system taken into account. The structural model may be composed of 99 substructures each with 7000 degrees of freedom. 300 panels may be used in the calculation of nonsteady aerodynamic forces and 50 modes in the flutter and gust response analysis. The data generation... HAJIFII is a program system developed by Chinese Aeronautical Establishment(CAE). It is able to accomplish the calculation of the modal characteristics of aircraft structures as well as the flutter and gust response analysis with the active control system taken into account. The structural model may be composed of 99 substructures each with 7000 degrees of freedom. 300 panels may be used in the calculation of nonsteady aerodynamic forces and 50 modes in the flutter and gust response analysis. The data generation system permits the flexible use of numerical data and topological description. 31 prescribed computational flows are supplied and an user can also organize his own computational flows as he needs. A structure can be discretized into finite elements or simulated by single spar. For the management of the stiffness and mass matrix a modified hypermatrix method is employed to omit all of inactive zero elements more effectively. A new algorithm, called a revised simultaneous iteration procedure, has been developed to solve the real eigenvalue problem and is more effective than the current agorithm. Modal synthesis technique with both free and fixed interfaces is adopted. Besides, two new methods of synthesis have been developed from the concept of multilevel substructures. Nonsteady aerodynamic forces are calculated by means of subsonic doublet lattice method for multiwings and aerodynamic forces in Laplace plane can be approximated with a curvefitting procedure based on sinusoidal data. Flutter equations are solved by Vg and pk methods and the continuous atmosphere turbulance are used in the gust response analysis. The system consists of a sequence of functional modules so it can be modified and extended easily. An advanced file management system has also been developed. There are approximately 26000 FORTRAN IV statements in the system. The HAJIFII was applied to analyzing a number of typical aircraft structures and gave good results.  HAJIFⅡ是中国航空研究院领导研制的航空结构动力分析系统。它可以进行结构的固有动力特性计算,以及带主动控制系统的飞机颤振计算和突风响应计算。它具有31条固定流程、2600条FORTRAN语句。允许使用99个原级子结构,每个子结构的自由度数可达7000。颤振计算和突风响应计算中,可以使用50个形态。非定常空气动力计算的分块数可达300个。在刚度矩阵和质量矩阵的管理上,采用超元矩阵方法做“宏观处理”,并用有效列方法做“微观处理”,发展了新的同时迭代算法,以提高实特征值计算的效率。设计了比较完整的形态综合法计算程序,除固定界面法和自由界面法之外,还发展了分级综合和逐步综合的新方法。非定常空气动力计算方面,引入了用曲线拟合方法把谐振荡空气动力转入拉氏平面的技术。用本系统计算了一批典型的结构,取得了良好结果。  In the unsteady transonic flow field of turbomachines, the existence of shocks may profoundly affect aeroelastic stability of cascade. However the shape, the number and the position of shocks are closely relative to a series of geometric and aerodynamic parameters of cascade, and are not easy to be specified beforehand. In order to enable us to consider the unsteady transonic flow past oscillating cascades of airfoils with shocks, a finite difference method was developed in this paper. In this method, the velocity... In the unsteady transonic flow field of turbomachines, the existence of shocks may profoundly affect aeroelastic stability of cascade. However the shape, the number and the position of shocks are closely relative to a series of geometric and aerodynamic parameters of cascade, and are not easy to be specified beforehand. In order to enable us to consider the unsteady transonic flow past oscillating cascades of airfoils with shocks, a finite difference method was developed in this paper. In this method, the velocity potential is separated into steady and unsteady parts, and the linear complex partial differential equation with spatially variable coefficients for the unsteady velocity potential of small disturbances is solved using transonic relaxation procedure.Some numerical results given here show that, for the unsteady transonic flow past oscillating cascades of which the inlet and the outlet Mach numbers are all less than 1.0, the existence of the shock at the end of local supersonic region has a marked influence. And this investigation has predicted the possibility of bending flutter at high subsonic inlet Mach number and low negative incidence.  在叶轮机械的非定常跨音流场中,激波会对气动弹性稳定性有很大影响。而激波的形状、数目、位置又与叶栅的一系列几何参数及气动参数密切相关,事先难以规定。为能考虑叶型叶栅的非定常跨音带激波绕流,本文发展了一种有限差分数值解法。其中速度势被分解为定常和非定常小扰动两部分,并用跨音松弛法求解关于非定常扰动速势的空问变系数线性复变量微分方程。 文中给出的一些数值结果表明,对于进出口M数均小于1.0的叶栅非定常跨音流动说来,局部超音区结尾处激波的存在有很大影响。本研究还预测到在高亚音进口M数,低负攻角条件下出现弯曲颤振的可能。   << 更多相关文摘 
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