Decay of grid turbulence in a closed box

We investigate the decay of a turbulent flow in the absence of mean flow. By accelerating a square grid in a water tank, we generate an array of wakes that induces a 3 dimensional turbulent flow with a Reynolds number of about Re $ \approx 5\times 10^4$. After the impulse excitation (about 100ms), a decay in time of this turbulent flow is observed. The entire decay process lasts for hours while the dissipative length rises up through scales over time. We follow and characterize both in space and time this turbulent decay process through several decades.