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직렬배열에 놓인 크기가 다른 정방형주의 유체력 저감특성
노기덕(Ki Deok Ro),강창환(Chang Whan Kang),박권호(Kwon Ho Park) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.7
본 연구는 고 레이놀즈 영역에서 상류측에 작은 정방형주(Square prism)를 가진 정방형주의 유동장 특성을 양 항력측정 실험과 PIV를 이용한 가시화 실험으로 파악한 것이다. 실험변수는 정방형주 한변의 길이에 대한 작은 정방형주의 폭비(H/B=0.2~0.6) 및 정방형주 전면에서부터 작은 정방형주의 후면까지의 거리(G/B=0~3)로 했다. 작은 정방형주의 폭비를 고정시킨 경우 정방형주의 항력감소율은 간격비가 증가할수록 증가하다 감소하는 특성을 보였다. 또한 같은 간격비에서는 작은 정방형주의 폭비가 클수록 정방형주의 항력감소율이 컸다. 또한 같은 간격비에서는 작은 정방형주의 폭비가 클수록 정방형주의 항력감소율이 증가했으며, 폭비 H/B=0.6, 간격비 G/B=1.0일 때 최대 98.0%의 항력감소율을 보였다. 정방형주의 양력감소율은 작은 정방형주의 폭비 및 간격비에 거의 영향을 받지 않았으며, 양력감소율의 전체 평균치는 66.5% 정도였다. 작은 정방형주를 설치한 경우 정방형주 상류측과 하류측에 정체영역이 나타났다. The Characteristics of the flowfields of a square prism having a small square prism were investigated by measuring of lift and drag on the square prism and visualizing the flowfield using PIV. The experimental parameters were the width ratios(H/B=0.2~0.6) of small square prisms to the prism width and the gap ratios (G/B=0~3) between the prism and the small square prism. The drag reduction rate of the square prism initially increased and then decreased with the G/B ratio for the same H/B ratio, and increased with the H/B ratio for the same G/B ratio. The maximum drag reduction rate of 98.0% was observed at H/B=0.6 and G/B=1.0. The lift reduction rate of the square prism was not affected by the width and gap ratios; the total average value was approximately 66.5%. In case of a square prism having a small square prism, the stagnation regions were represented in the upstream and downstream sides of the square prism.
노기덕(Ki-Deok Ro),김광석(Kwang-Seok Kim),오세경(Se-Kyeong Oh) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.11
The flow around a rotating circular cylinder near a plane wall is 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 are the rotating direction of the cylinder, the space ratios H/D(H/D=0.05~0.5) between cylinder and plane wall and the velocity ratios α(α=0~±2.0). In the case of clockwise, 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, 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.
노기덕(Ki-Deok Ro),김광석(Kwang-Seok Kim),김종현(Jong-Hyeon Kim) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.7
The Flow characteristics of a ship's propulsion mechanism of Weis-Fogh type, in which a airfoil(NACA0010) moves reciprocally in a channel, were investigated by the PIV. Velocity vectors and velocity profiles around the operating and stationary wings were observed at opening angles of α=15° and 30°, velocity ratios of V/U=0.5~1.5 and Reynolds number of Re=0.52×104~1.0×104. As the results the fluid between wing and wall was inhaled in the opening stage and was jet in the closing stage. The wing in the translating stage accelerated the fluid in the channel. And the flow fields of this propulsion mechanism were unsteady and complex, but those were clarified by flow visualization using the PIV.
노기덕(Ki Deok Ro),강명훈(Myeong Hoon Kang) 한국마린엔지니어링학회 2004 한국마린엔지니어링학회 학술대회 논문집 Vol.2004 No.-
Flow patterns around a rotating circular cylinder having Surface dimpled surface were visualized by the hydrogen bubble technique at velocity ratios from a=0 to 4.8 and Reynolds number of Re=l.0xl04. 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 a =0 to 4.1 and Reynolds number from Re=1.2xl04 to Re=2.0xl04. As the velocity ratios increase. 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 than that of the smooth cylinder.<br/> <br/>