Bulk statistics of stable and decaying Taylor-Couette turbulence

In this talk we focus on the velocity fluctuations in highly turbulent Taylor-Couette flow for the case of stable flow (constant rotation) and for decaying flow. Turbulent flows are generally characterized by the range of scales of their fluctuations, and a statistical description of the flow is often done by calculating the correlations of velocity fluctuations. These correlations are found to behave like power-laws over a range of scales, and their exponents characterize a certain geometry of flow. Many systems have been investigated carefully: Pipe-flow, Von Kármán flow, Rayleigh Bénard convection, \textit{et cetera}. There are, however, few reports \cite{lew99,she01} quantifying the turbulent properties in Taylor-Couette flow. In the presented work \cite{huisman2013b} we measure the longitudinal structure functions using laser Doppler anemometry, which is a non-intrusive technique and is able to measure the components of the velocity, and thus ideal for obtaining structure functions and the local velocity. We present the statistics of the turbulent velocity fluctuations for counter rotation for varying $a=-\omega_o/\omega_i$