Campagne Antoine, Gallet Basile, Moisy Frédéric, Cortet Pierre-Philippe
Laboratoire FAST, CNRS, Université Paris-Sud, 91405 Orsay, France.
Laboratoire SPHYNX, Service de Physique de l'État Condensé, CEA Saclay, CNRS UMR 3680, 91191 Gif-sur-Yvette, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Apr;91(4):043016. doi: 10.1103/PhysRevE.91.043016. Epub 2015 Apr 23.
We present a spatiotemporal analysis of a statistically stationary rotating-turbulence experiment, aiming to extract a signature of inertial waves and to determine the scales and frequencies at which they can be detected. The analysis uses two-point spatial correlations of the temporal Fourier transform of velocity fields obtained from time-resolved stereoscopic particle image velocimetry measurements in the rotating frame. We quantify the degree of anisotropy of turbulence as a function of frequency and spatial scale. We show that this space-time-dependent anisotropy is well described by the dispersion relation of linear inertial waves at large scale, while smaller scales are dominated by the sweeping of the waves by fluid motion at larger scales. This sweeping effect is mostly due to the low-frequency quasi-two-dimensional component of the turbulent flow, a prominent feature of our experiment that is not accounted for by wave-turbulence theory. These results question the relevance of this theory for rotating turbulence at the moderate Rossby numbers accessible in laboratory experiments, which are relevant to most geophysical and astrophysical flows.
我们展示了对一个统计平稳旋转湍流实验的时空分析，旨在提取惯性波的特征，并确定能够检测到它们的尺度和频率。该分析使用了从旋转坐标系中的时间分辨立体粒子图像测速测量获得的速度场的时间傅里叶变换的两点空间相关性。我们将湍流的各向异性程度量化为频率和空间尺度的函数。我们表明，这种时空相关的各向异性在大尺度上由线性惯性波的色散关系很好地描述，而较小尺度则由较大尺度上流体运动对波的扫掠主导。这种扫掠效应主要归因于湍流的低频准二维分量，这是我们实验的一个突出特征，而波湍流理论并未考虑到这一点。这些结果质疑了该理论对于实验室实验中可达到的中等罗斯比数下的旋转湍流的相关性，而这些罗斯比数与大多数地球物理和天体物理流动相关。
