Slow dynamics in a highly turbulent von K\'arm\'an swirling flow

In this work we present an experimental analysis of the dynamics of the coherent structures that appear in a von K\'arm\'an swirling flow, in a fully developped turbulent regime. The objective is to determine the effect of the fluctuations in the dynamics of these vortices. To achieve this goal, we have measured the flow in a water experiment. The fluid has been stirred in a cylindrical cavity up to a Reynolds number of $10^6$. We show that the average velocity field of the turbulent flow bifurcates subcritically breaking some symmetries of the problem and becomes time-dependent because of equatorial vortex moving with a precession movement. This subcriticality produces a bistable regime, with a hysteresis region for an extremely small range of parameters. Three different time-scales are relevant to the dynamics, two of them very slow compared to the impeller frequency. We have studied the different time scales of the system, changing a enclosure volume (neutrally buoyant spheres) assuming that the density of the sphere is homogeneous. Also we change the frequency of the impellers ($10 Hz$ - $50 Hz$) to explore another parameter of the system. We follow this volume in a period of time and we compare the results in different spatial scales.