The instability of the separated shear layer from a bluff body

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Abstract
It has generally been assumed in previous studies that the normalized shear-layer frequency (fSL/fK) versus Reynolds number (Re) varies as Re0.5. There has also been a great deal of scatter in quoted values of the critical Reynolds number (Recrit) for the onset of the shear-layer instability, with values ranging from 350 to 3000. In the present work, we find that Recrit is strongly sensitive to the mode of primary vortex shedding and may vary between 1200–2600 depending on the angle of oblique shedding. In the case of the shear-layer frequency, we have conducted a careful reevaluation of all previous data in the literature, and find the relationship fSL/fK=0.0235×Re0.67. Surprisingly, not one of the previous studies yields a relationship that is close to Re0.5. We suggest an explanation for the variation Re0.67 based on simple physical grounds.