Turbulence decay towards the linearly-stable regime of Taylor Couette

DNS of turbulence decay in Taylor-Couette flow in the linearly stable regime is presented. A fixed radius ratio $\eta=0.714$ is used, and initial Reynolds numbers of up to $Re\sim10^5$ are reached. Simulations are run in an axially-periodic domain, and thus completely lack the end-plates effects which are present in experiments and cause Ekman effects leading to a supercritical transition to turbulence. Here, we start with a fully turbulent state in the unstable regime and enter the linearly stable regime by suddenly starting a (stabilizing) outer cylinder rotation. This stabilization causes the system to behave as a damped oscillator and correspondingly the turbulence decays. The evolution of the torque and wind kinetic energy is analysed and the period and damping of the oscillations are quantified as a function of Reynolds number.