Dynamic of large particles embedded in shear flows

etc15 Tracking Number 372

Large particles ($D \gg \eta$) immersed in a closed turbulent flow tend to explore in a non-uniformly way the cavity in which they are placed. Here we study the slow dynamics of large particles (with various size) advected in closed turbulent flows at different Reynolds numbers. We investigate the spatial sampling experienced by large particles in two fully turbulent closed flows generated between counter-rotating disks (so called von Karman flow), focusing in the slow frequency's ($f_{slow} < \Omega$, where $\Omega$ is the rotation rate of the driving impellers) and characterize the power spectrum of the slow fluctuations of particles position. Both considered flows share a common feature : the presence of a shear region dividing two mean re-circulation regions ; however the spatial symmetries and the temporal behaviors of both setups are very different. The principal result in this research is that despite these differences both flows exhibit a well defined slow dynamical behavior that can be identified in Fourier space. We report on the universal characteristics of such slow motion.