论文标题
均匀旋转湍流中的多粒子拉格朗日统计
Multi-particle Lagrangian statistics in homogeneous rotating turbulence
论文作者
论文摘要
地球物理流通常是湍流的，并且会旋转。这种旋转改变了湍流的结构，因此有望明智地影响其拉格朗日特性。在这里，我们通过以不同的旋转速率使用直接的数值模拟来研究均匀旋转湍流中对，三合会和四核的相对分散和几何形状。表现出对垂直方向（沿旋转轴）的速度比在水平方向上要快。长期以来，在泰勒的制度中，这是由于与水平速度相比的垂直速度分量的去相关较慢。在短时间内，在弹道制度中，可以通过考虑发行时间的不同方向来解释该结果，并且是Eulerian二阶函数各向异性的签名。旋转还增强了均质和各向同性湍流中三合会和四方的失真。特别是，在长期以来，四局的变平随旋转速率增加。与我们对成对的观察值一致，三合会和四核的最大维度优先与旋转轴对齐。
Geophysical flows are often turbulent and subject to rotation. This rotation modifies the structure of turbulence and is thereby expected to sensibly affect its Lagrangian properties. Here, we investigate the relative dispersion and geometry of pairs, triads and tetrads in homogeneous rotating turbulence, by using direct numerical simulations at different rotation rates. Pair dispersion is shown to be faster in the vertical direction (along the rotation axis) than in the horizontal one. At long times, in Taylor's regime, this is due to the slower decorrelation of the vertical velocity component as compared to the horizontal one. At short times, in the ballistic regime, this result can be interpreted by considering pairs of different orientations at the release time, and is a signature of the anisotropy of Eulerian second-order functions. Rotation also enhances the distortion of triads and tetrads also present in homogeneous and isotropic turbulence. In particular, at long times, the flattening of tetrads increases with the rotation rate. The maximal dimension of triads and tetrads is shown to be preferentially aligned with the rotation axis, in agreement with our observations for pairs.
