Large scale correlations for energy injection mechanisms in swirling turbulent flows

We report an experimental study of large scale correlations in the power in jected in turbulent swirling flows generated in the gap between two coaxial rotating disks. We measure the pressure fluctuations on the blades of one disk, as well as the pressure drop between the leading and the trailing edg es of the rotating blades, i.e, the local drag force. Measurements at diffe rent positions on one blade and on two successive blades display a correlat ion length much larger than the ones usually expected in turbulent flows. T he time lag for which the correlation between two points is maximum, strong ly depends on the global flow configuration. These results help us to under stand the statistical properties of the injected power fluctuations in turb ulent swirling flows.