Periodic wakes of low aspect ratio cylinders with free hemispherical ends

The wakes of circular cylinders with free hemispherical ends and of differe nt aspect ratios (length-to-diameter ratios) are experimentally studied for moderate Reynolds numbers. This investigation is restricted to cylinders w ith low aspect ratios, namely less than 5, and includes the case of the sph ere. The transition to nonstationarity of the how in these cylinder wakes i s the main focus of this work: the results show that the stability of wakes is strongly dependent on aspect ratio and is also affected by the free-end conditions. We characterize the frequency, amplitude and phase as well as the critical Reynolds number of the periodic vortex shedding regime. (C) 20 01 Academic Press.