Transient turbulence in Taylor-Couette flow.

Recent studies have brought into question the view that at sufficiently high Reynolds number turbulence is an asymptotic state. We present direct observation of the decay of turbulent states in Taylor-Couette flow with lifetimes spanning five orders of magnitude. We also show that there is a regime where Taylor-Couette flow shares many of the decay characteristics observed in other shear flows, including Poisson statistics and the coexistence of laminar and turbulent patches. Our data suggest that for a range of Reynolds numbers characteristic decay times increase superexponentially with increasing Reynolds number but remain bounded in agreement with the most recent data from pipe flow. Our data are also consistent with recent theoretical predictions of lifetime scaling in transitional flows.