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이철희,배귀남,최항철,이춘식,Lee, C.H.,Bae, G.N.,Choi, H.C.,Lee, C.S. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.3
In this study, indoor thermal parameters were measured to investigate the characteristics of thermal environments and 212 occupants were questioned to evaluate Korean thermal comfort in office building in summer. Thermal and comfort sensations were estimated using PMV(Predicted Mean Vote) and ET* (New Effective Temperature) which are most widely used nowadays. Comparing this experimental result with international standards and that of other research, Korean thermal responses were discussed. It was found that TSV(Thermal Sensation Vote) is more sensitive than PMV to the variation of temperature and that the measured percentage of dissatisfied is higher than PPD(Predicted Percentage of Dissatisfied) in real office building environments. By regression analysis, the following regression equation has been obtained: TSV=0.461ET*-11.808 and neutral temperature is $25.6^{\circ}C$ in this case. Thermal comfort range based on 80% satisfaction is also $24.0{\sim}26.8^{\circ}C$, which is about $1^{\circ}C$ higher than that of ANSI/ASHRAE Standard.
날개 길이방향 유동과 날개 회전이 날개짓 운동의 공기역학적 특성에 미치는 효과
오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.9
3-D 날개짓 운동은 왕복운동과 회전운동으로 구성된다. 3-D 날개짓 운동은 왕복운동하는 동안 날개 길이방향의 유동이 발생된다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 회전에 의한 순환이 발생한다. 본 연구에서는 날개 길이방향 유동과 날개 회전이 3-D 날개짓 운동의 공기역학적 특성에 미치는 영향을 알아보기 위하여 3-D 날개짓 운동과 2-D 병진운동을 비교하였다. 각각의 날개짓 운동에서 받음각과 레이놀즈수에 따라 공력을 측정하였다. 2-D 병진운동의 공력이 3-D 날개짓 운동의 공력 보다 크다. 하지만 3-D 날개짓 운동시 발생되는 양력은 왕복운동의 중반부에서 받음각 50˚까지 증가하였고 2-D 병진운동시 발생되는 양력은 받음각 30˚이상에서 감소하였다. 또한 각각의 왕복운동의 끝에서 날개 회전에 의하여 공력이 급격하게 증가하였다. In a 3-D flapping motion, the spanwise flow is generated while the wing is moved on the stroke plane. And at the end of each stroke, the rotational circulation is generated due to a wing rotation. In this study, to evaluate the effect of spanwise flow and wing rotation on the aerodynamic characteristics in 3-D flapping motion, a 3-D flapping motion was compared with a 2-D translating motion. In each flapping motion, the aerodynamic forces were measured with respect to the angles of attack and Reynolds number. The aerodynamic forces generated by 2-D translating motion were higher than those generated by 3-D flapping motion. While the lift of 3-D flapping motion was increased until the angle of attack 60˚ at mid-stroke, the lift generated by 2-D translating motion was decreased above the angle of attack 40˚ at mid stroke. Also, at the end of each stroke, the aerodynamic forces were increased rapidly due to wing rotation.
날개의 종횡비가 날개 짓 운동의 공기역학적 특성에 미치는 영향
오현택(Hyun-Taek Oh),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The lift and drag forces produced by a wing of a given cross-sectional profile are dependent on the wing planform and the angle of attack. Aspect ratio is the ratio of the wing span to the average chord. For conventional fixed wing aircrafts, high aspect ratio wings produce a higher lift to drag ratio than low ones for flight at subsonic speeds. Therefore, high aspect ratio wings are used on aircraft intended for long endurance. However, birds and insects flap their wings to fly in the air and they can change their wing motions. Their wing motions are made up of translation and rotation. Therefore, we tested flapping motions with parameters which affect rotational motion such as the angle of attack and the wing beat frequency. The half elliptic shaped wings were designed with the variation of aspect ratio from 4 to 11. The flapping device was operated in the water to reduce the wing beat frequency according to Reynolds similarity. In this study, the aerodynamic forces, the time-averaged force coefficients and the lift to drag ratio were measured at Reynolds number 15,000 to explore the aerodynamic characteristics with the variation of aspect ratio. The maximum lift coefficient was turned up at AR=8. The mean drag coefficients were almost same values at angle of attack from 10° to 40° regardless of aspect ratio, and the mean drag coefficients above angle of attack 50° were decreased according to the increase of aspect ratio. For flapping motion the maximum mean lift to drag ratio appeared at AR=8.