円柱の下流に十字交差配置された帯状の平板による振動制御 : 第2報,帯状平板による渦励振の励起と抑制(流体工学,流体機械)  [in Japanese] Vibration Control for a Circular Cylinder by a Strip-Plate Set Downstream in Cruciform Arrangement : 2nd Report, Generation and Suppression of Vortex Excitation on Elastically Supported Cylinder(Fluids Engineering)  [in Japanese]

The specific aim of this work is to develop a new technique to control vortex excitations of a circular cylinder by utilizing interference of a downstream strip-plate in cruciform arrangement. In the previous paper, it is shown that the two longitudinal vortices, trailing vortex and necklace vortex, shed in the vicinity of the crossing of a fixed circular cylinder/strip-plate system. In this paper, the circular cylinder was supported elastically so as to allow cross-flow motion and influence of the strip-plate on vortex excitation was investigated with the same wind tunnel apparatus. The strip-plate suppresses Karman vortex excitation more effectively compared with a downstream circular cylinder. A wider strip-plate has a larger suppression effect. The trailing vortex induces vortex excitation when gap-to-diameter ratio s/d less than 0.3. When the strip-plate width w is equal to the upstream circular cylinder diameter d, the velocity range for longitudinal vortex excitation is 5 times wider than the case of the downstream circular cylinder. The necklace vortex excitations dose not occur for strip-plates with w/d≥0.75, as expected from the fixed-cylinder experiment. Longitudinal vortex excitation by downstream strip-plate occurs over a wide velocity range, and it can be easily controlled by s/d adjusting.