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151.
The effects of co-current flows on a rising Taylor bubble are systematically investigated by a front tracking method coupled with a finite difference scheme based on a projection approach. Both the upward (the co-current flows the same direction as the buoyancy force) and the downward (the co-current moves in the opposite direction of the buoyancy force) co-currents are examined. It is found that the upward co-current tends to elongate the bubble, while the downward co-current makes the bubble fatter and shorter. For large Nf (the inverse viscosity number), the upward co-current also elongates the skirted tail and makes the tail oscillate, while the downward co-current shortens the tail and even changes a dimpled bottom to a round shape. The upward co-current promotes the separation at the tail, while the downward co-current suppresses the separation. The terminal velocity of the Taylor bubble rising in a moving flow is a linear combination of the mean velocity (UC) of the co-current and the terminal velocity (U0) of the bubble rising in the stagnant liquid, and the constant is around 2 which agrees with the literature. The wake length is linearly proportional to the velocity ratio (UC/U0). The co-currents affect the distribution of the wall shear stresses near the bubble, but not the maximum. 相似文献
152.
The paper presents a new study on a tri-layer thin plate.Shadow moiré implemented with an advanced phase unwrapping technique is employed to obtain actual flexural deformation of a real-life plate sample subjected to thermal loads.An analytical model is re-formulated to provide the plate with global closed-form solutions of the plate deflection as well as the interfacial stress and strain.With the measurements and the solutions available,an inverse iterative approach is developed to evaluate and maximize th... 相似文献
153.
证明了由Lévy过程驱动的反射型倒向随机微分方程在局部Lipschitz系数下的解的存在唯一性,并且研究了解的稳定性质.此外,当系数满足Lipschitz条件以及反射壁正则时,证明了过程K的正则性. 相似文献
154.
155.
运用线性回旋动力学与磁流体力学的混合模拟程序,研究了JT-60U和JT-60SA装置中高能量粒子对离散阿尔芬本征模的共振激发.发现了丰富的αTAE动力学不稳定模式,研究了它的不稳定特性对高能量粒子速度的依赖关系.发现在JT-60U高βp ELMy H模运行中有grassy ELM的放电比有gaint ELM的放电更容易被高能量粒子激发成不稳定模式,在有边缘L模存在的负剪切运行下的各个势阱中都存在高能量粒子激发的αTAE不稳定模式.另外在JT-60SA中高βp全非感应电流驱动下的模拟实验放电下也发现了丰富的αTAE不稳定模式,观察了αTAE在该装置中沿磁场线和径向两个方向的二维广域本征模特性. 相似文献
156.
刘国芬 《数学的实践与认识》2013,43(1)
讨论了Bernstein-Sikkema-Bézier算子点态逼近的等价定理,首先利用插项的的方法证明了正定理,然后应用讨论算子逼近的常规方法给出了其逼近的逆定理. 相似文献
157.
158.
159.
Front propagation is a ubiquitous phenomenon. It arises in physical, biological and cross-disciplinary systems as diverse as flame propagation, superconductors, virus infections, cancer spread or transitions in human prehistory. Here we derive a single, approximate front speed from three rather different time-delayed reaction–diffusion models, suggesting a general law. According to our approximate speed, fronts are crucially driven by the lag times (periods during which individuals or particles do not move). Rather surprisingly, the approximate speed is able to explain the observed spread rates of completely different biophysical systems such as virus infections, the Neolithic transition in Europe, and postglacial tree recolonizations. 相似文献
160.
Yong LIU Jianglun WU Fengxia YANG Jianliang ZHAI 《Frontiers of Mathematics in China》2011,6(6):1147-1183
In this paper, we study an ergodic theorem of a parabolic Andersen model driven by Lévy noise. Under the assumption that A = (a(i, j))
i,j∈S
is symmetric with respect to a σ-finite measure gp, we obtain the long-time convergence to an invariant probability measure ν
h
starting from a bounded nonnegative A-harmonic function h based on self-duality property. Furthermore, under some mild conditions, we obtain the one to one correspondence between
the bounded nonnegative A-harmonic functions and the extremal invariant probability measures with finite second moment of the nonnegative solution
of the parabolic Anderson model driven by Lévy noise, which is an extension of the result of Y. Liu and F. X. Yang. 相似文献