AI 中文总结
该研究给出纬向地转流态下快速旋转湍流中相对扩散和湍流扩散的首次实验测量，通过合成拉格朗日轨迹计算相关统计量，揭示了不同区域转变，还能据此测量湍能耗散率和湍流扩散率，测量结果与相关理论大致相符。
AI 中文摘要
我们给出了在纬向地转流态下快速旋转湍流中相对扩散和湍流扩散的首次实验测量，即在存在瞬时且占主导地位的纬向急流的情况下。从时间分辨实验速度场计算合成拉格朗日轨迹，据此测量相对（双粒子）扩散。计算了基于时间和基于分离的统计量，包括累积逆分离时间（CIST），在惯性范围（直接涡度级联和逆能量级联）以及扩散区域有其解析预测。这些统计量显示了从大于能量注入尺度的理查森区域到大于过渡尺度（由于湍流涡旋与罗斯比波相互作用湍流变得各向异性的尺度）的扩散区域的转变。CIST的解析预测使我们能够测量理查森区域的湍能耗散率和扩散区域的湍流扩散率。我们对扩散率的测量与混合长度和纬向地转理论的预测大致一致，但表明对能量耗散率的依赖较浅。
英文摘要
We present the first experimental measures of relative dispersion and turbulent diffusion in rapidly-rotating turbulence in the zonostrophic regime, i.e., in the presence of instantaneous and dominant zonal jets. Synthetic Lagrangian trajectories are computed from time-resolved experimental velocity fields, from which we measure relative (two-particle) dispersion. Time-based and separation-based statistics are calculated, including the cumulative inverse separation time (CIST), for which analytical predictions exist in the inertial ranges (direct enstrophy cascade and inverse energy cascade) and in the diffusive regime. These statistics show evidence of a transition from a Richardson regime at scales larger than the energy-injection scale, to a diffusive regime, at scales larger than the transitional scale, the scale at which turbulence becomes anisotropic due to the interaction between turbulent eddies and Rossby waves. The analytical predictions for the CIST allow us to measure the turbulent energy dissipation rate in the Richardson regime, and the turbulent diffusivity in the diffusive regime. Our measurements of diffusivity are broadly consistent with predictions from mixing-length and zonostrophic theories but suggest a shallower dependence on the energy dissipation rate.
Comments24 pages, 9 figures
