We simultaneously measure both spinning and tumbling components of rotation for long near-neutrally buoyant fibers in homogeneous and isotropic turbulence. The lengths and diameters of the measured fibers extend to several orders of the Kolmogorov length of the surrounding turbulent flow. Our measurements show that the variance of the spinning rate follows a $-4/3$ power-law scaling with the fiber diameter $\left(d\right)$ and is always larger than the variance of the tumbling rate. This behavior surprisingly resembles that observed previously for sub-Kolmogorov fibers. These observations suggest that long fibers preferentially align with vortex filaments that can be as long as the integral length of turbulence. We compute the Lagrangian timescale and the distribution of both tumbling and spinning that supports this outlook. Our measurements also allow us to quantify the importance of the Coriolis term on the rotational dynamics of fibers in turbulent flows.

中文翻译：

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各向同性湍流中长纤维的纺丝和翻滚

我们同时测量均质和各向同性湍流中较长的近中性浮力纤维的旋转的旋转和翻转分量。被测纤维的长度和直径延伸到周围湍流的Kolmogorov长度的几个数量级。我们的测量结果表明，纺丝速度的方差遵循$-4/3$ 幂律随光纤直径缩放 $（d）$并且总是大于翻滚速度的方差。该行为令人惊讶地类似于先前对于亚科莫莫洛夫纤维观察到的行为。这些观察结果表明，长纤维优先与涡流丝对齐，涡流丝的长度可以与湍流的整体长度一样长。我们计算了拉格朗日时间尺度以及支持该前景的翻滚和旋转的分布。我们的测量结果还使我们能够量化科里奥利项对湍流中纤维旋转动力学的重要性。