Analysis of vortex populations in turbulent wall-bounded flows
Analysis of vortex populations in turbulent wall-bounded flows
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DOI：
10.1017/jfm.2011.101
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发表时间：
2011-04
影响因子：
3.7
通讯作者：
Q. Gao;C. Ortiz-Dueñas;E. Longmire
中科院分区：
文献类型：
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作者：
Q. Gao;C. Ortiz-Dueñas;E. Longmire
利用壁面湍流的速度场识别和表征了旋涡结构。DeláLamo等人在Reτ=934时获得了两组充分发展的明渠水流的直接数值模拟数据。(《流体力学》，第500卷，2004年，第135页)和Reτ=590，由Moser，Kim&Mansour(Phys.流体，第11卷，1999年，第943页)，以及由Ganapathisubramani，Longmire&Marusic(Phys.)获得的零压力梯度湍流边界层中z+=110时的双平面粒子图像测速数据，Reτ=1160.流体，2006年第18卷，055105)。采用基于局部速度梯度张量的三维旋涡强度来识别涡核位置。利用张量的实特征向量来改进识别算法，并确定每个涡核的方位。这种识别方法可以分析几乎所有方向的岩心。利用投影到实特征向量方向上的涡量向量计算了每个涡旋结构的环流。然后计算了不同壁面法线位置的不同种群分布，包括核的大小、取向、环流和传播速度。所识别出的中心的平均半径随着壁法向距离的增大而增大，平均环流随涡半径的增大而近似二次增加。强环流中心的取向分布范围比弱环流中心小得多，与前倾型发夹结构的腿、颈、头一致。
Vortical structures were identified and characterized using velocity fields of turbulent wall-bounded flows. Two direct numerical simulation data sets of fully developed channel flow at Reτ = 934 obtained by del Álamo et al. (J. Fluid Mech., vol. 500, 2004, p. 135) and Reτ = 590 obtained by Moser, Kim & Mansour (Phys. Fluids, vol. 11, 1999, p. 943) as well as dual-plane particle image velocimetry data at z+ = 110 in a zero-pressure-gradient turbulent boundary layer at Reτ = 1160 obtained by Ganapathisubramani, Longmire & Marusic (Phys. Fluids, vol. 18, 2006, 055105) were employed. The three-dimensional swirling strength based on the local velocity gradient tensor was employed to identify vortex core locations. The real eigenvector of the tensor was used both to refine the identification algorithm and to determine the orientation of each vortex core. The identification method allowed cores of nearly all orientations to be analysed. Circulation of each vortical structure was calculated using the vorticity vector projected onto the real eigenvector direction. Various population distributions were then computed at different wall-normal locations including core size, orientation, circulation and propagation velocity. The mean radius of the cores identified was found to increase with increasing wall-normal distance, and the mean circulation increases approximately quadratically with eddy radius. Orientations of cores with stronger circulation were distributed over a much narrower range than those for vortices with weaker circulation and were consistent with legs, necks and heads of forward-leaning hairpin structures.