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The content of this research is divided by three small subjects and the abstract of each subject is as follows : 1. Flow field characteristics of a rotating circular cylinder having square dimpled surface Flow patterns around a rotating circular cylinder having square dimpled surface were visualized...

The content of this research is divided by three small subjects and the abstract of each subject is as follows : 1. Flow field characteristics of a rotating circular cylinder having square dimpled surface Flow patterns around a rotating circular cylinder having square dimpled surface were visualized by the hydrogen bubble technique at velocity ratios from α=0 to 4.8 and Reynolds number of Re = 1.0 × 10^(4). The wake region of the cylinder was reduced as the velocity ratios increase and was smaller than that of the smooth cylinder without dimples at the same velocity ratio. The hydrodynamic characteristics on the cylinder was investigated by measuring of lift and drag at velocity ratios from α=0 to 4.1 and Reynolds number from Re=1.2 × 10^(4) to Re=2.0 × 10^(4). As the velocity ratios increased, the average lift and drag coefficients were increased. And at the same velocity ratio, the average lift was larger but the average drag was smaller with the existence of dimple. 2. Magnus effect of a rotating circular cylinder near a plane Wall The Magnus effect of a rotating circular cylinder near a plane wall was investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters were the rotating direction of the cylinder, the space ratios H/2r (H/2r = 0.05 ~0.5) between cylinder and plane wall and the velocity ratios α(α=0 ~± 2.0). In the case of clockwise direction, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise direction, the absolute value of the lift on the rotating circular cylinder was increased with the space ratios and with the velocity ratios, the lower separation point was more shifted in the rotating direction with them. 3. Magnus effect of a rotating circular cylinder having square dimpled surface near a plane wall The Magnus effect of a rotating circular cylinder having the square dimpled surface near a plane wall was investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique. The results were compared with those of the smooth cylinder. In the case of clockwise, the separation point of the cylinder having the dimples was more shifted in the rotating direction and the average lift coefficient was larger than that of the smooth cylinder. In the case of anticlockwise, the separation point of the smooth cylinder was more shifted in the rotating direction and the average lift coefficient was larger in negative direction than that of the cylinder having the square dimpled surface. The absolute value of the average lift coefficient was increased with the velocity ratios regardless of the rotating direction and the existence of dimples of the cylinder.

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