Quantitative Velocity Measurements in Turbulent Taylor-Couette Flow by Flow Tagging

Abstract

Quantitative velocity measurements have been performed in Taylor-Couette flow using the PHANTOMM flow tagging technique. The results illustrate the expected three-dimensional features of the flow including the presence of well defined Taylor cells at low Taylor numbers and gradual transition to turbulence as the Taylor number is increased. The spectral density and auto correlation functions were computed over the Taylor number range 21.1 × 103 to 1.10 × 1011. For Taylor numbers less than approximately 6 × 107, the flow is dominated by large toroidal eddies with a wavelength the same order as the gap size. As the Taylor number is increased above this value, the flow displays more irregular motions, associated with the Gortler instability or instability of the second kind. Nevertheless, even for the highest Taylor number studied in this work, the structure is far from random, and the flow exhibits an almost periodic behavior. The results show the potential of the PHANTOMM technique to investigate spatial instabilities in confined flows.