Orientation patterns of non-spherical particles in turbulence*

In experiments and numerical simulations we measured angles between the orientations of small spheroids in turbulence. Since turbulent strains tend to align nearby spheroids, one might think that their relative angles are quite small. We show that this intuition fails in general: the distribution of relative angles has heavy power-law tails, and the dynamics evolves to a fractal attractor despite the fact that the fluid velocity is spatially smooth at small scales. The fractal geometry depends on particle shape,  and it determines the power-law exponents. This talk is based on: Zhao, Gustavsson, Ni, Kramel, Voth, Andersson & Mehlig, arxiv:1707.06037