Decay of turbulence at high Reynolds numbers

etc15 Tracking Number 418

Using the unique capabilities of the Variable Density Turbulence Tunnel at the Max Planck Institute for Dynamics and Self-Organization, we investigated virtually homogeneous and isotropic grid turbulence over a wide range of Reynolds numbers, $Re = UM/\nu$, between $10^4$ and $5\cdot 10^6$. The choice of pressurizable Sulfur Hexafluoride as a working gas makes it possible to reach extremely high Reynolds numbers without changing boundary conditions. Indeed, the Reynolds number we reached were higher than any previous classical grid wind-tunnel experiment. In this talk, we focus on the fundamental question of how fast turbulent energy decays once it has been created, and show that the Reynolds number plays no important role in setting the decay rate if it is high enough.