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排序方式: 共有280条查询结果,搜索用时 140 毫秒
271.
跨音速轴流压气机叶顶间隙泄漏流对微喷气的非定常响应机制和扩稳效果研究 总被引:2,自引:0,他引:2
本文将叶顶微喷气方法应用于 NASA Rotor37 跨音速轴流压气机转子,在近失速工况,利用数值模拟方法研究了不同喷气量时叶顶间隙泄漏流对微喷气的非定常响应机理和叶顶微喷气的扩稳效果.结果表明,喷气使得叶顶区域的叶表压力随喷嘴与叶片相对位置的变化沿弦向发生波动,抑制了叶顶泄漏流的自激非定常波动,使叶顶泄漏流轨迹沿叶片吸力面向下游移动,实现了提高压气机性能和稳定性的目的.采用喷射气流的无量纲总动量可关联亚音速和跨音速轴流压气机不同喷气方案的扩稳效果,该无量纲总动量与来流总动量和喷射气流高度成反比,而与叶高和喷射气流总动量成正比. 相似文献
272.
273.
Bifurcation and chaos analysis for aeroelastic airfoil with freeplay structural nonlinearity in pitch
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The dynamics character of a two degree-of-freedom
aeroelastic airfoil with combined freeplay and cubic stiffness
nonlinearities in pitch submitted to supersonic and hypersonic flow
has been gaining significant attention. The Poincaré mapping
method and Floquet theory are adopted to analyse the limit cycle
oscillation flutter and chaotic motion of this system. The result
shows that the limit cycle oscillation flutter can be accurately
predicted by the Floquet multiplier. The phase trajectories of both
the pitch and plunge motion are obtained and the results show that
the plunge motion is much more complex than the pitch motion. It is
also proved that initial conditions have important influences on the
dynamics character of the airfoil system. In a certain range of
airspeed and with the same system parameters, the stable limit cycle
oscillation, chaotic and multi-periodic motions can be detected
under different initial conditions. The figure of the Poincaré
section also approves the previous conclusion. 相似文献
274.
V. V. Vedeneev 《Fluid Dynamics》2009,44(2):314-321
In classical investigations of panel flutter it is usually assumed that the gas pressure acting on the plate can be calculated within the framework of the piston theory, an approximation exact for high Mach numbers. The loss of stability revealed in these investigations is of the “coupled” type, involving the interaction of two oscillation modes. Recently, the use of asymptotic methods revealed another single-mode type of stability loss, which cannot be obtained within the framework of the piston theory. In the present study this type of stability loss is investigated numerically using the Bubnov-Galerkin method. 相似文献
275.
基于流场定常化的桥梁颤振分析简化数值方法 总被引:1,自引:1,他引:0
基于数值方法实现快速有效地分析评价大跨桥梁颤振稳定性.针对强迫振动法识别颤振导数试验中的大跨桥梁二维节段模型.利用RNG κ-ε湍流模型并采用有限体积法求解桥梁模型绕流二维不可压缩流体Navier-Stokes方程.通过计算桥梁断面模型在周期运动中少数离散时刻的气动力,利用最小二乘法计算颤振导数,采用SCANLAN方法求解颤振临界风速,最终进行颤振稳定性分析.通过该方法计算出了丹麦Great Belt East桥和我国虎门大桥的颠振临界风速.计算结果与已有试验结果十分接近,进而验证了该数值方法的有效性和可靠性. 相似文献
276.
B. A. Khudayarov 《International Applied Mechanics》2008,44(6):676-682
The nonlinear flutter of some aircraft elements is modeled. A viscoelastic model is used. Numerical algorithms for solving
integro-differential equations are developed. The critical flutter speed and time for a viscoelastic plate are determined
__________
Translated from Prikladnaya Mekhanika, Vol. 44, No. 6, pp. 97–104, June 2008. 相似文献
277.
Anthony N. Kounadis 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2006,57(2):324-349
The dynamic local stability of autonomous Hamiltonian, weakly damped, lumped-mass (discrete) systems is reconsidered. For
such potential(conservative) systems conditions for the existence of limit cycles are discussed by studying the effect of
the damping matrix on the Jacobian eigenvalues. New findings that contradict existing results are presented. Thus, undamped
stable symmetric systems with the inclusion of slight damping may experience: (a) a double zero eigenvalue bifurcation, a
degenerate Hopf bifurcation and a generic (usual) Hopf bifurcation, and (b) a limit cycle (dynamic) mode of instability prior
to the static (divergence) mode of instability (failure of Zieglers kinetic criterion). A variety of numerical examples verified
by a nonlinear analysis confirm the validity of the theoretical findings presented herein.
Received: January 3, 2003; revised: July 14, 2003 and February 17, 2004 相似文献
278.
最大负荷设计之:角区分离预测与控制 总被引:2,自引:0,他引:2
角区分离对叶轮机性能有重要影响.本文根据角区流动特征推导出描述角区三维附面层的等效二维附面层模型,并结合二维附面层分离准则,建立了角区分离判定准则.理论分析表明:为抑制角区分离,应尽量增大叶表吸力面与端壁相交二面角;为抑制角区分离,应使二面角α沿流向逐渐增大,或使二面角α沿流向逐渐减小过程尽量平缓,尤其在二面角α较小区域更应如此.鉴于此,建议风扇/压气机设计中应严格监控角区二面角大小及二面角流向变化梯度,以实现对角区分离的良好控制.结论也适用于其它叶轮机. 相似文献
279.
Fusheng Wang Shihui Huo Shengjun Qiao Junran Zhang Zhufeng Yue 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(1):58-76
Static aeroelastic and flutter characteristics of an aircraft composite wing with high aspect ratio were analysed by an effective Computational Fluid Dynamics and Computational Structure Dynamics coupled method. Effects of stiffness distribution on aeroelastic characteristics were considered. Honeycomb core sandwich composite was considered to be equivalent to an orthotropic material by stiffness and inertance equivalent method to allow highly efficient numerical simulation, which was used for analysis of bending and torsional stiffness distribution. The results showed that the redistributed aerodynamic load leads to a decrease of pressure difference between the upper and lower airfoils. The flutter speed of the composite wing is near 0.64 Ma. Both bending and torsional stiffness increases with a small increase of beam size. Stiffness of the wing root has a major influence generally on the static aeroelastic characteristics. Both the lift coefficient and the loss percent decrease with a small increase of beam size. Effects of stiffness distribution on frequency are not obvious. Flutter speed remains close to the initial value when the beam size is changed. 相似文献
280.
基于涡流发生器的翼型失速流动控制及雷诺数效应影响研究 总被引:1,自引:0,他引:1
针对所设计的三角形涡流发生器开展用于翼型失速流动控制的风洞实验研究,重点讨论涡流发生器几何参数、方向角、安装位置及实验雷诺数等因素对翼型失速流动控制的影响。实验结果表明:涡流发生器作用下,在干净翼失速迎角后能够形成一个升力几乎不随迎角变化的相对稳定的高升力状态,抑制了失速流动的发生,与此同时阻力大幅下降;本文所设计的涡流发生器方向角过大时会削弱翼型失速流动控制的效果;同一涡流发生器作用下雷诺数过大其失速流动控制效果会急剧恶化,第一种涡流发生器控制翼型失速的雷诺数有效范围略宽于第二种涡流发生器。 相似文献