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991.
This work aims to develop and validate a numerical model to simulate the flow-structure interaction in tube bundles subjected to two-phase flow. The model utilizes a mixture multiphase module in which a drift flux formulation is used to account for the slip between the phases. Two methods of numerical flow-structure interaction are used to predict the onset of fluidelastic instability (FEI) in the streamwise direction for a two-phase air–water flow mixture in parallel triangular tube bundles. These models are the hybrid analytical-flow field model and the direct numerical flow/structure coupling model. This work investigates the effects of void fractions in the range of 20% to 80% and several pitch-to-diameter ratios (P/D) in the range of 1.3 to 1.7. The results of the fluidelastic forces and the stability threshold are validated against the experimental data available in the literature and show an excellent agreement. The streamwise FEI threshold shows a significant dependency on the pitch-to-diameter ratio while the void fraction exhibits a lesser effect. Generally, the stability threshold increases as the pitch-to-diameter ratio increases. The model that was developed paves the way for devising of more reliable prediction tools for FEI in steam generators. 相似文献
992.
Interface coupling effects of weakly nonlinear Rayleigh–Taylor instability with double interfaces 下载免费PDF全文
Taking the Rayleigh–Taylor instability with double interfaces as the research object,the interface coupling effects in the weakly nonlinear regime are studied numerically.The variation of Atwood numbers on the two interfaces and the variation of the thickness between them are taken into consideration.It is shown that,when the Atwood number on the lower interface is small,the amplitude of perturbation growth on the lower interface is positively related with the Atwood number on the upper interface.However,it is negatively related when the Atwood number on the lower interface is large.The above phenomenon is quantitatively studied using an analytical formula and the underlying physical mechanism is presented. 相似文献
993.
The effect of inhomogeneous fluctuations on instabilities in various nonlinear chemical models is studied in terms of concepts developed in the theory of equilibrium phase transitions.Chercheur qualifié au Fonds National de la Recherche Scientifique. 相似文献
994.
Using a scheme given by Marco, we prove that partially hyperbolic tori along resonant surfaces of near-integrable Hamiltonian systems possess the obstruction property in Arnold's terminology. The proof is based on a specific lambda lemma for these tori. 相似文献
995.
本文考察了由烧蚀稀疏形成的流体密度分布和烧蚀波阵面上非线性热传导效应对烧蚀波Rayleigh-Taylor不稳定性的影响。得到烧蚀稀疏区流体的不稳定性加剧烧蚀波阵面不稳定性的结论。发展了“火抛光”效应致稳作用的解析论证。 相似文献
996.
Kai Shoichi Fukunaga Hidehiko Brand Helmut R. 《Journal of statistical physics》1989,54(5-6):1133-1152
We study the influence of external multiplicative noise on the electrohydrodynamic instability (EHD) in nematic liquid crystals. It turns out that the correlation time
n
and the intensityQ of the noise are the crucial parameters to control the system. Different types of noise lead to minor quantitative changes when compared to Gaussian white noise, leaving the qualitative aspects unchanged. With increasing noise intensity the threshold for the onset of the first instability changes drastically. We observe that the curvature arising when the threshold of the various instabilities is plotted as a function of the noise intensity changes as one is going, e.g., from the onset of Williams domains (WD) to the onset of the grid pattern (GP). This result reflects the transition in the flow structure from two-dimensional (WD) to three-dimensional (GP, DSM) flow patterns. As the intensity of the noise is increased further, the onset of the first instability becomes more complex. The measurement of the nonlinear onset time shows a strong dependence on the noise intensityQ, which is linear for WD and GP well above onset. The linear onset time shows an unexpected dependence on the noise intensity close to the onset of the first instability. For sufficiently long correlation times of the noise, a destabilization by noise is obtained. 相似文献
997.
Basic theoretical and experimental results of research into natural-convective instability of electrochemical systems are considered. 相似文献
998.
Sanjay Mittal 《国际流体数值方法杂志》2009,59(9):1035-1049
999.
The NBTI degradation phenomenon and the role of hydrogen during NBT stress
are presented in this paper. It is found that PBT stress can recover a
fraction of Vth shift induced by NBTI. However, this recovery is
unstable. The original degradation reappears soon after reapplication of the NBT
stress condition. Hydrogen-related species play a key role during a device's NBT
degradation. Experimental results show that the diffusion species are
neutral, they repassivate Si dangling bond which is independent of the gate
voltage polarity. In addition to the diffusion towards gate oxide, hydrogen
diffusion to Si-substrate must be taken into account for it also has
important influence on device degradation during NBT stress. 相似文献
1000.
二维超音速边界层中三波共振和二次失稳机制的数值模拟研究 总被引:2,自引:1,他引:1
通过直接数值模拟的方法,探讨在超音速边界层的转捩问题中,是否存在和不可压缩流情况相似的产生亚谐波的机制.结果表明,三波共振和二次失稳这两种机制都存在.讨论了这两种机制在层流至湍流的转捩中的重要性是否的确很大的问题. 相似文献