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Nishi, Yasuyuki,Inagaki, Terumi,Li, Yanrong,Omiya, Ryota,Hatano, Kentaro Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4
The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.
Yasuyuki Nishi,Terumi Inagaki,Yanrong Li,Ryota Omiya,Kentaro Hatano 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.4
The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.
Detection of planet candidates around K giants. HD 40956, HD 111591, and HD 113996
Jeong, G.,Lee, B.-C.,Han, I.,Omiya, M.,Izumiura, H.,Sato, B.,Harakawa, H.,Kambe, E.,Mkrtichian, D. Springer-Verlag 2018 Astronomy and astrophysics Vol.610 No.-
<P><I>Aims. </I>The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. </P><P><I>Methods. </I>We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G-K type giants. </P><P><I>Results. </I>In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield <I>P</I> = 578.6 ± 3.3 d, <I>m</I> sin <I>i</I> = 2.7 ± 0.6 <I>M</I>J, <I>a</I> = 1.4 ± 0.1 AU for HD 40956; <I>P</I> = 1056.4 ± 14.3 d, <I>m</I> sin <I>i</I> = 4.4 ± 0.4 <I>M</I>J, <I>a</I> = 2.5 ± 0.1 AU for HD 111591; <I>P</I> = 610.2 ± 3.8 d, <I>m</I> sin <I>i</I> = 6.3 ± 1.0 <I>M</I>J, <I>a</I> = 1.6 ± 0.1 AU for HD 113996. </P>