  The rotational dynamics of anisotropic particles advected in a turbulent
fluid flow are important in many industrial and natural setting. Particle
rotations are controlled by small scale properties of turbulence that are
nearly universal, and so provide a rich system where experiments can be
directly compared with theory and simulations. Here we report the first
three-dimensional experimental measurements of the orientation dynamics of
rod-like particles as they are advected in a turbulent fluid flow. We also
present numerical simulations that show good agreement with the experiments and
allow extension to a wide range of particle shapes. Anisotropic tracer
particles preferentially sample the flow since their orientations become
correlated with the velocity gradient tensor. The rotation rate is heavily
influenced by this preferential alignment, and the alignment depends strongly
on particle shape.
