Abstract
The present aim is to clarify the combination effect of curvature and streamwise thickness of a ring with rectangular cross sections, which is immersed perpendicularly to uniform flow. In a wind tunnel, the authors carried out the measurements using a deadweight gauge and hot-wire anemometers, and the flow visualisations by a smoke-wire method, for wide rages of Re, d/w and t/w, where Re, d, w and t are the Reynolds number, mean diameter, cross-section width and cross-section thickness of the ring, respectively. Consequently, the Strouhal number St, which is a reduced frequency of regular vortex shedding from the ring, is independent of d/w, t/w and Re. On the other hand, base suction depends not on Re, but on d/w and t/w. Considering d/w and t/w as governing parameters, and regarding to base suction, flow visualisation, velocity fluctuation, mean-velocity profile, turbulence-intensity profile and four-points velocity correlation, we can classify the flow into four flow modes; viz., an over-critical axisymmetrical mode, a sub-critical axisymmetrical mode, a sub-critical non-axisymmetrical mode and a sub-critical less-correlation mode.
