Abstract
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 power-law scaling with the fiber diameter 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.
1 More- Received 16 November 2020
- Accepted 23 March 2021
DOI:https://doi.org/10.1103/PhysRevFluids.6.044610
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