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981.
约束阻尼层板的振动分析 总被引:5,自引:0,他引:5
约束阻尼层结构是一类利用阻尼层的剪切效应达到减振目的的结构。基于这一原理,本文分析了约束阻尼层板的振动。引入的位移模式中,考虑了附加部分对原结构运动的相对性和阻尼层的横向剪切效应,据此推导了约束阻尼层板的运动方程和边界条件。最后分析了简支矩形板的固有振动,讨论其振动特点。 相似文献
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Liu Jixue Tang Dengbin YangYingzhao 《中国航空学报》2007,20(4):313-319
The process of evolution, especially that of nonlinear evolution, of C-type instability of laminar-turbulent flow transition in nonparallel boundary layers are studied by means of a newly developed method called parabolic stability equations (PSE). Initial conditions, which are very important for the nonlinear problem, are investigated by computing initial solution of the harmonic waves, modifying the mean-flow-distortion, and giving initial value of TS wave and its subharmonic waves at initial station by solving linear PSE. A numerical method with high-order accuracy are developed in the text, the key normalization conditions in the PSE are satisfied, and nonlinear PSE are solved efficiently and implemented stably by the spatial marching. It has been shown that the computed process of nonlinear evolution of C-type instability in Blasius boundary layer is in good agreement with the experimental results. 相似文献
987.
首先对比了天上飞行状态与地面风洞状态下钝锥边界层的转捩特性,然后利用基于线性稳定性理论的eN方法对飞行状态与风洞状态下的钝锥边界层进行了转捩预示,最后研究了壁温比对高速钝锥边界层的稳定性及转捩的影响。研究结果表明,在低壁温比条件下,圆锥迎风中心与侧面的边界层先于两者之间区域转捩,转捩形貌与飞行实验结果相似;在高壁温比条件下,圆锥迎风面区域迟于侧面及背风面区域转捩,转捩形貌与风洞试验结果相似。壁温比是造成高速钝锥边界层转捩天地差异的重要影响因素。 相似文献
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《中国航空学报》2020,33(7):1929-1941
Aero-optical effects for starlight transmission in the high-speed flow field will reduce the accuracy of the star sensor on an aircraft. Numerical simulations for aero-optical effects usually require plenty of calculations, which cause difficulties when designing a celestial navigation system for a high-speed aircraft. In this study, an Aero-Optical Simulator For Starlight Transmission (AOSST) in the boundary layer is developed. It effectively reduces the computational burden compared to that of the widely used CFD simulation, and it achieves satisfactory accuracy. In this simulator, gas ellipsoids satisfying certain design rules are used to simulate coherent density structures in boundary layers. Design rules for the gas ellipsoids are found from published experimental and high-fidelity CFD simulation results. The generated wavefront distortion by AOSST is anchored with the scale law for aero-optical distortion in the boundary layer by determining some control parameters, which enables the simulator to output reliable results over a wide range of flight states. Four numerical examples are provided to verify the performance of AOSST. The results demonstrate that AOSST is able to simulate the directional dependence of aero-optical distortions in boundary layers, the variation trend of distorted wavefront shapes with Reynolds number, and the grayscale distribution on the disturbed star map. 相似文献
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