Anisotropic Helmholtz and wave–vortex decomposition of one-dimensional spectra
Anisotropic Helmholtz and wave–vortex decomposition of one-dimensional spectra
复制标题
一维光谱的各向异性亥姆霍兹和波涡分解
DOI：
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发表时间：
2017
影响因子：
3.7
通讯作者：
E. Tabak
中科院分区：
文献类型：
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作者：
O. Bühler;M. Kuang;E. Tabak
我们提出了一个扩展的各向异性流动的最近开发的亥姆霍兹和波涡分解方法的一维谱测量沿着船舶或飞机的轨道在Bühler等人。（J.流体机械，第756卷，2014年，pp. 1007-1026）。这里，各向异性指的是底层流场的统计特性，在原始方法中，该流场被假设为在水平面中是均匀和各向同性的。现在，允许流动具有以自洽方式选择的简单类型的水平各向异性，并且可以从水平速度场的一维功率谱及其互相关推导出。关键的结果是，在这种各向异性流设置中可以实现水平动能谱的精确和鲁棒的亥姆霍兹分解，然后还允许随后的波涡分解步骤。各向异性方法与各向同性方法一样易于使用，并且如果观察到的各向异性趋于零，则它会稳健地收敛回各向异性方法。作为我们分析的副产品，我们还发现了旋转流和发散流分量之间统计相关性的简单测试。新方法的理论开发和测试具有挑战性的合成数据，以及从墨西哥湾流的海洋数据令人鼓舞的结果。
We present an extension to anisotropic flows of the recently developed Helmholtz and wave–vortex decomposition method for one-dimensional spectra measured along ship or aircraft tracks in Bühler et al. (J. Fluid Mech., vol. 756, 2014, pp. 1007–1026). Here, anisotropy refers to the statistical properties of the underlying flow field, which in the original method was assumed to be homogeneous and isotropic in the horizontal plane. Now, the flow is allowed to have a simple kind of horizontal anisotropy that is chosen in a self-consistent manner and can be deduced from the one-dimensional power spectra of the horizontal velocity fields and their cross-correlation. The key result is that an exact and robust Helmholtz decomposition of the horizontal kinetic energy spectrum can be achieved in this anisotropic flow setting, which then also allows the subsequent wave–vortex decomposition step. The anisotropic method is as easy to use as its isotropic counterpart and it robustly converges back to it if the observed anisotropy tends to zero. As a by-product of our analysis we also found a simple test for statistical correlation between rotational and divergent flow components. The new method is developed theoretically and tested with encouraging results on challenging synthetic data as well as on ocean data from the Gulf Stream.