EFFECT OF FREESTREAM CONDITIONS ON THE FAR WAKE OF A CIRCULAR-CYLINDER

Hot-wire anemometry was incorporated to measure the frequency spectra at various downstream locations in the wake of a two-dimensional circular cylinder at a Reynolds number of 1.4 × 10. Two different freestream conditions were imposed on the wake to study the dependence of the wake spectra on background noise. The prominent frequencies observed in the wake showed significant dependence on freestream conditions. Moreover, all of the spectral peaks could be identified as sums or differences between the Karman frequency and prominent freestream frequencies or their harmonics or sums or differences between two or more prominent freestream peaks independent of Karman frequency. This implies that the far-wake structures arise due to hydrodynamic instability of the wake and that the associated frequencies of these structures are dependent on nonlinear interactions between the existing wake structures and disturbances in the freestream. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.