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以Del-Alamo等(2004)直接数值模拟的槽道紊流数据为基础,对比两种涡旋方向的计算方法(涡量矢量和速度梯度张量的实特征向量),并统计了涡旋与3个切面(XZ,XY及YZ)间倾角的概率密度分布.研究结果表明,在缓冲层内,涡量矢量与实特征向量存在较大的差异;涡旋以准流向涡为主,其与XZ面的倾角很小,但与YZ面的倾角很大.在缓冲层外,涡量矢量与实特征向量的夹角较小,且概率密度最大的夹角稳定在10°附近;涡旋以发夹涡为主,与XZ面主要呈±45°倾角,与XY及YZ面主要呈±55°倾角.涡旋与切面间倾角的概率密度分布特征可以由Ω状发夹涡模型来解释.
Based on the direct numerical simulation of channel turbulence data by Del-Alamo et al. (2004), the two methods of vortex direction computation (real eigenvectors of vorticity vectors and velocity gradient tensors) are contrasted. The results show that there is a big difference between the vorticity vector and the real eigenvector in the buffer layer. The vortices are dominated by quasi- The angle of inclination of XZ plane is small, but the angle of inclination with YZ plane is very large. Outside the buffer layer, the included angle of vorticity vector and real eigenvector is small, and the angle with the largest probability density is stable around 10 °. The hairpin vortex is dominated by ± 45 ° inclination from the XZ plane and ± 55 ° inclination from the XY and YZ planes.The distribution of the probability density of vortex-section inclinations can be explained by the Ω-shaped hairpin vortex model.