http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : 안윤수(Yun Soo Ahn) (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
-
나선형 핀이 부착된 원주후류의 2차원 난류특성에 관한 연구
안윤수(Yun Soo Ahn),남청도(Chung Do Nam) 한국해양대학교 해사산업연구소 2000 海事産業硏究所論文集 Vol.10 No.-
본 논문에서는 나선형 핀이 붙은 원주 후방의 2차원 난류후류를 정온형 열선유속계를 사용하여 실험적으로 조사하였다. 실험에 사용한 3종류의 모델중 2종류는 원주에 나선형 핀이 부착된 것이고 나머지 한 종류는 핀이 붙지 않은 평원주이며 이 모델들의 외경은 모두 31.4mm로 똑 같다. 원주로부터 유동방향으로 무차원화 한 X/D=5~20의 범위에 대하여 유동특성을 조사하였으며, 이 때의 레이놀즈 수는 Re=1.24×10⁴이다. 후류특성으로서 평균속도분포, 난류운동에너지, 자기상관계수 그리고 스펙트럼을 조사한 결과 나선형 핀이 붙은 원주의 경우에도 칼만(Karman)와의 방출이 분명히 존재하며, 핀의 치수가 작을수록 핀이 조밀하게 감긴 경우가 성기게 감긴 경우보다 후류 폭이 크게 되며 또 와 방출의 주파수가 낮아진다는 사실이 입증되었다. In this paper, two-dimensional turbulent wake flow behind a circular cylinder with helical fin was investigated experimentally by using the linearized constant temperature hot wire anemometer. Three experimental models were used in this study; two circular cylinders with helical fin and a plain circular cylinder. The out diameter of those models are the same width of 31.4mm. Turbulent characteristics were investigated for the range of X/D=5~20 downstream from the cylinder. The Reynolds number is 1.24x10⁴ based on the experimental model diameter and inlet velocity. The distribution of the mean velocity, turbulent kinetic energy, autocorrelation coefficient and its spectrum were measured. As a result it was made clear that Karman vortex shedding was clearly formed even in the case of a cylinder with helical fin. And it was also found that the width of the wake flow becomes large as the pitch of the fin increase, and the frequency of vortex shedding decrease.
-
노기안(Kee An Roh),김필주(Pil Joo Kim),강기경(Kee Kyung Kang),안윤수(Yoon Soo Ahn),윤성호(Seong Ho Yun) 한국환경농학회 1999 한국환경농학회지 Vol.18 No.3
To establish the best rice cultivating system in the aspects of environment-loving agriculture, the amounts and patterns of nitrogen leached in the paddy soil were investigated with 7 treatments; Recommendation(R), Farmer`s usual practice(FUP), Straw compost+chemical fertilizers reduced(SCF), Fresh straw+recommendation(FSC), Fresh cow manure(FCM), Cow manure compost(CMC), and no fertilization as Control(C). And SCF, FCM and CMC were applied with same amounts of total nitrogen to R. The infiltrated water samples were collected in ceramic porous cups which were buried at 60㎝ depth from the top. Concentrations of nitrate-N in irrigated water were 1.3㎎ ℓ^(-1) on rice transplanting season when nutrients began to elute from paddy soil, and 0.4㎎ ℓ^(-1) after breaking off irrigation. But it was 4-6㎎ ℓ^(-1) in rice growing period. The maximum concentration of nitrate-N in leachate was not more than 7㎎ ℓ^(-1) during rice cultivation. The amounts of nitrogen leached in R, FUP, SCF, FSR, FCM, CMC and C were 59, 63, 25, 41, 24, 27, 17㎏ ㏊^(-1)y^(-1) respectively. Nitrogen leaching was decreased to about 30% by supplement of fresh rice straw(FSC) to R. Furthermore, it was possible to reduce to over 50% of nitrogen leaching by reducing chemical fertilizer application(CF), or by substituting of chemical fertilizers with fresh cow manure(FCM) or cow manure compost(CMC). In added organic fertilizer treatments, the amounts of infiltrated nitrogen were less 13-46㎏ ㏊^(-1)y^(-1) than that of input by irrigation. This experiment showed that nutrients leaching was minimized by substitution of chemical fertilizers with organic fertilizer or by application of straw with chemical fertilizers in rice paddy soil and rice cultivation with suitable fertilizer management can work as a purifier rather than contaminator of water.
ScienceON연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
