Experimental investigations of the spherical Taylor-Couette flow

Transition to turbulence of a viscous incompressible fluid flow between two concentric spheres with the inner one rotating and the outer stationary was investigated experimentally. The flow modes were studied using the flow visualization and electrochemical technique. Different flow states were obtained for the gap/radius ratio 0.107 in function of the Taylor number in the interval (22 - 1500) and aspect ratio (17 - 21). Observed states were classified into: Taylor Vortex Flow (TVF), Spiral Mode (SM), Spiral Mode Wavy Mode (SM+WM), Spiral Wavy Mode (SWM), Wavy Mode (WM) and Chaos. The variations of the flow patterns were reflected by the wall velocity gradient, its fluctuation and spectral analysis. Fast Fourier transform applied on the time series of the wall velocity gradient allowed for the analysis and identification of the fundamental frequencies and their evolutions associated with each flow state