Reduction of bluff-body drag and suppression of vortex shedding by the introduction of wavy separation lines

The results of an experimental investigation to study the influence of spanwise waviness of the separation lines on the flow around common bluff forms are presented. Wind-tunnel measurements were made on thin plates normal to the flow and on rectangular cross-section bodies at Reynolds numbers of about 40 000. The plates have a spanwise sinusoidal form and the front faces of the rectangular bodies are also sinusoidal. Compared to the equivalent straight bodies, drag reductions of up to at least 30% are achieved. Also, for ratios of peak-to-peak wave height divided by wavelength in excess of between 0.06 and 0.09, vortex shedding is completely suppressed. (C) 1998 Academic Press Ltd.