Galvanostatic water electrolysis was conducted in 2 wt % KOH and 0.1 N H 2 SO 4 solutions under microgravity. The corresponding terrestrial experiments employed two kinds of electrode configurations: a vertical cathode and downward-facing horizontal cathode-over-anode ͑C/A͒ arrangement. The latter configuration was designed to simulate the microgravity ͑-G͒ condition. The ohmic resistance of the gas bubble dispersion zone near Pt electrodes was measured by the current interrupter method and compared for these three different cases. The transient variation of resistance for C/A configuration behaved similarly to that under -G in H 2 SO 4 , but the resistance varied more slowly in KOH. When water electrolysis was conducted with a vertical plane cathode under 1-G, the resistance reached an essentially constant value within a few 100 ms in KOH, whereas the resistance increased linearly for a few seconds, followed by a zig-zag variation in H 2 SO 4 . Water electrolysis under -G resulted in stable froth layer formation, and the accompanying ohmic resistance increased in linear proportion to the froth layer thickness. The contributions of electrode surface coverage by bubbles and electrolyte-phase bubble void fraction to the ohmic drop were also assessed. These parameters were compared with corresponding values in terrestrial experiments analyzed by Balzer and Vogt.
西条市役所 建設道路課(〒793-8601 愛媛県西条市明屋敷164)
学生員 九州工業大学大学院 工学研究科博士前期課程Fishways have been constructed to facilitate migration of fish at dams, waterfalls and rapids. Although a lot of types of fishway are suggested, most of the fishways installed in Japanese rivers belong to the pool-and-weir type. Several values such as a water level difference between the upstream and downstream, the ratio between the flow depth and streamwise pool length, the shape of the weir and so on have an influence on the suitability of migration. In particular, Nakamura pointed out that the suitability of migration is greatly affected by the location of notch. However, this indication is not verified quantitatively. In this study, the trajectories of the migrating fish were recorded with two sets of digital video cameras and also velocity measurements were conducted in the pool-and-weir fishway with alternate notch and also with one-sided notch. It was found that the trajectories are different between alternate notch case and one-sided notch case. This is because the velocity and its direction in the pool is different from each other.
Fishways are river constructions which give a helping to fish migration. There are three types of flow formations in pool-and-weir fishways such as a plunging flow, streaming flow and intermixed flow of plunging and streaming flows. Rajaratnam et al. proposed a criterion formula that predicts the flow formations. However, this criterion formula has no physical meaning. Further the accuracy of prediction of their formula is not high. In this study, the criterion formula, which can predict the flow formation in a pool-and-weir fishway, is derived semi-theoretically. The experiments were conducted with changing the aspect ratio and discharge in the pool-and-weir fishway. The water surface profiles were measured and also three components velocities were measured with a 3-D electromagnetic current meter. A new criterion formula, which is able to predict the flow formation, is proposed under the condition that the channel slope is 1 on 12.
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