ON THE TRANSITION OF THE CYLINDER WAKE

The transition of the cylinder wake is investigated experimentally in a water channel and is computed numerically using a finite-difference scheme. Four physically different instabilities are observed: a local "vortex-adhesion mode," and three near-wake instabilities, which are associated with three different spanwise wavelengths of approximately 1, 2, and 4 diam. All four instability processes can originate in a narrow Reynolds-number interval between 160 and 230, and may give rise to different transition scenarios. Thus, Williamson's [Phys. Fluids 31, 3165 (1988)] experimental observation of a hard transition is for the first time numerically reproduced, and is found to be induced by the vortex-adhesion mode. Without vortex adhesion, a soft onset of three-dimensionality is numerically and experimentally obtained. A control-wire technique is proposed, which suppresses transition up to a Reynolds number of 230. © 1995 American Institute of Physics.