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Watanabe, Satoshi,Momosaki, Shimpei,Usami, Satoshi,Furukawa, Akinori Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.2
An application of contra-rotating rotors, in which a rear rotor is in tandem with a front one and these rotors rotate in the opposite direction each other, has been proposed against a demand for developing higher specific speed axial flow pump. One prototype rotors, which we have designed with a conventional method, has given the positive slope of head characteristic curve especially in the rear rotor. It is necessary to understand the internal flow behavior in the rear rotor to establish the design guideline for achieving higher and more reliable performance. In the present study, we carried out the experimental investigations of the internal flow field of the rear rotor, especially at the partial flow rate, by Laser Doppler Velocimetry (LDV) for the main flow and the limiting streamlines observation on rotor surfaces for the boundary layer flows.
Satoshi FUTAI,Kazuto SETO,Ryo WATANABE,Yuichi IWASAKI,Mitsuru MIYAZAKI,Toru WATANABE 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-
This paper proposes a new type of active seismo-meter measuring vibration possessing long period and wide dynamic range. In order to lower the natural frequency and expand the detectable amplitude, the sensor with the low natural frequency is realized by using feedback control. Besides, analog feedback control circuit consisted of resistors, capacitors and operational amplifiers possess temperature dependency, while digital feedback control circuit consisted of computer and digital signal processor is temperature independent. In this report, a novel digital feedback control circuit is developed and tested to avoid temperature dependency. It has been demonstrated that the detectable frequency range and the dynamic range of that is expanded.
Prediction of Cavitation Surge Onset Point by One-Dimensional Stability Analysis
Satoshi Watanabe,Yoshinobu Tsujimoto 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.2
Cavitation instabilities such as rotating cavitation and cavitation surge often occur in high speed turbopumps. It has been shown by a stability analysis that the cause of cavitation instabilities is explained by the positive mass flow gain factor, representing the increase of cavity volume against the decrease (increase) of flow rate (incidence angle). The cavitation compliance, representing the increase of cavity volume in response to the decrease of inlet pressure, determines the frequency of instabilities. However, one-dimensional stability analysis cannot be directly used for the prediction of the onset point of cavitation surge when quasi-steady assumption is applied. In the present study, unsteady characteristics, i.e. the phase lag in the response of cavity volume against the flow rate/inlet pressure fluctuations, are taken into account in a stability analysis of cavitation surge in the form of lag element. The onset criterion considering the time lag is newly proposed for one-dimensional stability analysis, and the criterion is validated by comparisons with a two-dimensional stability analysis based on a singularity method applied to a free streamline theory.
Internal Flow of a Two-Bladed Helical Inducer at an Extremely Low Flow Rate
Watanabe, Satoshi,Inoue, Naoki,Ishizaka, Koichi,Furukawa, Akinori,Kim, Jun-Ho Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.2
The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.
Satoshi Watanabe,Kai Shimokawa,Akinori Furukawa,Kusuo Okuma,Daisuke Matsushita 한국유체기계학회 2012 International journal of fluid machinery and syste Vol.5 No.1
A two dimensional Darrieus-type turbine has been proposed for the hydropower utilization of extra-low head less than 2m. In a practical use of Darrieus-type hydro-turbine, head and flow rate may be varied temporally and seasonally. Considering that the cost advantage is required for the low head hydro turbine system, the Darrieus turbine should be operated with high efficiency in the wider range of flow rate possibly by using an additional device with simpler mechanism. In the present paper, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed to obtain the preferable inlet velocity in low flow rate conditions. Effects of resulting spanwise partial inlet flow are investigated. Finally, an effective modification of inlet nozzle height over flow rate variation is shown.
Watanabe, Satoshi,Shimokawa, Kai,Furukawa, Akinori,Okuma, Kusuo,Matsushita, Daisuke Korean Society for Fluid machinery 2012 International journal of fluid machinery and syste Vol.5 No.1
A two dimensional Darrieus-type turbine has been proposed for the hydropower utilization of extra-low head less than 2m. In a practical use of Darrieus-type hydro-turbine, head and flow rate may be varied temporally and seasonally. Considering that the cost advantage is required for the low head hydro turbine system, the Darrieus turbine should be operated with high efficiency in the wider range of flow rate possibly by using an additional device with simpler mechanism. In the present paper, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed to obtain the preferable inlet velocity in low flow rate conditions. Effects of resulting spanwise partial inlet flow are investigated. Finally, an effective modification of inlet nozzle height over flow rate variation is shown.
( Satoshi Motoya ),( Mamoru Watanabe ),( Hyo Jong Kim ),( Young Ho Kim ),( Dong Soo Han ),( Hirotoshi Yuasa ),( Junichi Tabira ),( Naoki Isogawa ),( Shoko Arai ),( Isao Kawaguchi ),( Toshifumi Hibi ) 대한장연구학회 2018 Intestinal Research Vol.16 No.2
Background/Aims: Tofacitinib is an oral, small-molecule Janus kinase inhibitor being investigated for ulcerative colitis (UC). In OCTAVE Induction 1 and 2, patients with moderately to severely active UC received placebo or tofacitinib 10 mg twice daily (BID) for 8 weeks. Clinical responders in OCTAVE Induction were re-randomized to 52 weeks’ therapy with placebo, tofacitinib 5 mg BID, or tofacitinib 10 mg BID. Methods: We conducted post-hoc efficacy and safety analyses of East Asian patients in OCTAVE Induction 1 and 2 and OCTAVE Sustain. Results: A total of 121 East Asian (Japan, Korea, and Taiwan) patients were randomized in OCTAVE Induction 1 and 2 (placebo, n=26; tofacitinib 10 mg BID, n=95), and 63 in OCTAVE Sustain (placebo, n=20; tofacitinib 5 mg BID, n=22; tofacitinib 10 mg BID, n=21). At week 8 of OCTAVE Induction 1 and 2, 18.9% of patients (18/95) achieved remission with tofacitinib 10 mg BID versus 3.8% (1/26) with placebo. In OCTAVE Sustain, the week 52 remission rates were 45.5% (10/22), 47.6% (10/21), and 15.0% (3/20) with 5 mg BID, 10 mg BID, and placebo, respectively. Adverse event rates were similar between groups in OCTAVE Induction and numerically higher with tofacitinib in OCTAVE Sustain. Serious adverse event rates were similar across groups in all studies. Infections were numerically more frequent with tofacitinib than placebo. Increases in serum lipid levels were observed with tofacitinib. Conclusions: In East Asian patients with UC, tofacitinib demonstrated numerically greater efficacy versus placebo as induction and maintenance therapy, with a safety profile consistent with the global study population. ClinicalTrials.gov: NCT01465763; NCT01458951; NCT01458574. (Intest Res 2018;16:233-245)
Satoshi Miyauchi,Yukio Watanabe 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
BaTiO3/(La,Sr)2CuO4 multilayered lms are epitaxially grown on [001] SrTiO3 single crystals. X-ray diffractometry shows that the BaTiO3 layer is a mixture of a- and c-axis-oriented regions. The current-voltage characteristics of the lms are measured between RT and 150 C, and the temperature (T) dependence of the conductivity of the lms is deduced. The as-grown lms show mostly activation-type T-dependence of but exhibit an abrupt change typically once of twenty times. When the lms are post-annealed, the lms constantly exhibit anomalous abrupt changes in the T-dependence of