Transient states in plane Couette flow

We present the rich and complex relaxation dynamics of turbulent plane Couette flow when the Reynolds number is lowered. In particular, we reveal the existence of well-defined transient states around which the dynamics of turbulent retreat is organized. We characterize these states in physical space and we propose a projection of these states in phase space to understand their nature. The results presented have been obtained in an experiment in which we perform annealing and quenching, i.e. gentle or sudden decreases in Reynolds number. The nature of asymptotic states is also studied and shown to depend on the final Reynolds number, but not at all on the rate of change of the Reynolds number.