【作者】 凌国灿； 赵红亮； 牛家玉；

【Author】 Ling Guo-can Zhao Hong-liang Niu Jia-yu (LNM, Institute of Mechanics, Chinese Academy of Sciences. Beijing 100080 China, ; Research Centerfor Fluid Dynamics, College of Science, PLA University of Science and Technology, Nanjing 211101, China; LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080,China)

【机构】 中国科学院力学研究所LNM国家重点实验室； 解放军理工大学理学院流体力学研究中心；

【摘要】 本文用高精度紧致有限差分与Fourier谱方法,通过对三维不可压N-S方程的直接数值模拟计算,研究具有展向不同非均匀性的尾遗型流动时空发展的基本特征和转捩性态。所研究的流动包括来流沿展向呈指数衰减型的局部非均匀流、台阶型非均匀流等两类典型情况。数值结果表明流动不稳定性的非线性发展及空间非均匀发展导致旋涡脱落在相位、频率和强度上的差异。在变化率最大的地方出现展向涡量向流向及垂向的显著转变,形成不同类型的旋涡位错。用流动关键物理量及涡线详细刻画了旋涡位错的结构特征和动力学过程,描述了旋涡位错中复杂的三维涡链。利用FFT方法分析了流动中速度的时空变化及旋涡位错对流动转捩的影响。更多还原

【Abstract】 In present work vortex dislocations in wake-type incoming flows with two kinds of spanwise nonuniformity have been studied in detail by DNS, namely, by solving directly three-dimensional Navier-Stokes equations, based on compact finite difference-spectral methods with high accuracy and resolutions. The characteristics and dynamics as well as their effects on flow transitions of vortex dislocations are reported. The results show that the nonuniformity and instability of the incoming flows lead to the deviation of two-dimensional K rm n vortex streets in frequency, phase and strength along the span of the flows. Iso-surfaces of vorticity and vortex line tracks in flow field clearly present the dynamical process of dislocation generation and the real vortex linkages in the vortex dislocations. The effects of vortex dislocation on flow transitions are described by FFT analysis.更多还原