Three-dimensional structure of ordered and chaotic vortex streets behind circular cylinders at low Reynolds numbers

Abstract

We have investigated the spatial and temporal structure of certain cases of chaotic and organized vortex shedding in self-excited cylinder wakes at low Reynolds number (40–200) by extending hot-wire measurements to much larger downstream locations than our earlier measurements (Van Atta and Gharib, 1987) and performing concurrent smoke-wire flow visualizations. We describe here results for two cases in which chaotic vortex shedding is observed. The first is the single-vibration frequency locked-in case, in which the most highly disturbed regions of the vortex street, which produce chaotic spectra, are confined to compact spanwise-periodic propagating disturbed regions. The second is the multiple-vibration frequency case in which chaotic velocity spectra are observed at all spanwise locations.

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