A look at a universal parameter for 2-D and 3-D bluff body flows

Abstract

The flow behind a circular cylinder in the subcritical Reynolds number regime was investigated through the use of hot wire and mean pressure measurements. Cylinder taper and shear flow were used to study the effect of three-dimensionality on the flow, and base-mounted splitter plates were used to modify the formation region of nominally two-dimensional configurations. Measurements provide an extensive set of formation region data for a variety of bluff body configurations. Comparisons between the different parameters suggest that the base-pressure, shear layer velocity, and the size of the formation region were strongly coupled. The concept of a universal Strouhal parameter that would remain invariant for a variety of bluff bodies was investigated using nondimensional combinations of the measured parameters. The previously defined universal parameter formulations, which use the Strouhal number multiplied by the ratio of the normalized wake width to the base-pressure parameter, failed to converge for most of the three-dimensional configurations. The cause of that failure is identified by the relationship between the base-pressure parameter and the wake width that causes their ratio to diverge. A modification is proposed that consists of using the product of the two parameters instead of the ratio. This proposed modification is shown to produce the most invariant parameter for the data measured in this investigation. © 1996 Academic Press Limited.