标题： 无剪切湍流混合中的小尺度各向异性 显示英文标题

标题： Small scale anisotropy in turbulent shearless mixing

摘要： 在无剪切湍流混合中生成小尺度各向异性进行了数值研究。 在泰勒雷诺数介于45到150之间的直接数值模拟数据表明，不仅纵向速度导数矩与均匀各向同性湍流中的值有显著差异，而且跨过混合层和沿混合层的分量的偏度变化符号相反。 由于存在动能梯度而引起的各向异性模式与由均匀剪切产生的模式非常不同。 事实上，在混合中横向导数矩被发现非常小，这表明横向矩的小并不足以说明各向同性。 显示英文摘要

摘要： The generation of small-scale anisotropy in turbulent shearless mixing is numerically investigated. Data from direct numerical simulations at Taylor Reynolds' numbers between 45 and 150 show that there is not only a significant departure of the longitudinal velocity derivative moments from the values found in homogeneous and isotropic turbulence, but that the variation of skewness has an opposite sign for the components across the mixing layer and parallel to it. The anisotropy induced by the presence of a kinetic energy gradient has a very different pattern from the one generated by an homogeneous shear. The transversal derivative moments in the mixing are in fact found to be very small, which highlights that smallness of the transversal moments is not a sufficient condition for isotropy.