Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Soichi Yamaguchi Last modified date:2019.07.23

Assistant Professor / Fluid Environmental Research / Department of Advanced Environmental Science and Engineering / Faculty of Engineering Sciences

2. Simon Waldman, Soichi Yamaguchi, R. O’Hara Murray, D. Woolf, Tidal resource and interactions between multiple channels in the Goto Islands, Japan., International Journal of Marine Energy,, 19, 332-344, 2017.09, The Goto Islands in Nagasaki Prefecture, Japan, contain three parallel channels that are suitable for tidal energy development and are the planned location for a tidal energy test centre. Energy extraction is added to a 3D numerical hydrodynamic model of the region, using a sub-grid momentum sink approach, to predict the effects of tidal development.
The available resource with first-generation turbines is estimated at 50–107 MW peak output. Spreading turbine thrust across the whole cross-section to prevent bypass flow results in a 64% increase in peak power in one channel, highlighting the importance of 3D over 2D modelling.
The energy available for extraction in each strait appears to be independent of the level of extraction in other straits. This contrasts with theoretical and numerical studies of other multi-channel systems. The weak interactions found in this study can be traced to the hydraulic effects of energy extraction not extending to neighbouring channels due to their geometry..
3. Soichi Yamaguchi, Yuichi Hayami, Impact of Isahaya dike construction on DO concentration in the Ariake Sea, Journal of Oceanography,, 74, 6, 565-586, 2017.11, In the Ariake Sea, dike construction in Isahaya Bay in 1997 for reclamation and disaster prevention was thought to cause big anthropogenic impacts on the marine ecosystem. Currently, hypoxia or anoxia occurs every summer in Isahaya Bay and the inner Ariake Sea. However, the effects of the dike construction on the DO concentration are unclarified. The present study evaluated the impact of the dike construction on the DO concentration by applying a numerical ecosystem model. The present calculation showed that the dike construction could affect the DO concentration in summer in wider area than reported before in the steady state with neap-spring tidal cycle. In Isahaya Bay, the DO concentration decreased by greater than 2.0 mg l-1 caused by the dike construction. It was generated by the decrease in DO supply due to the vertical diffusion process with the reduction of tidal current and the intensification of the density stratification. The dike construction also affected the DO concentration in the inner Ariake Sea by decreasing the DO concentration of the water transported by the estuarine circulation and the reduction of the diffusive supply of oxygen vertically with enhanced stratification by the dike construction. This study showed for the first time that the dike construction could affect the DO concentration in wide area of the Ariake Sea with the numerical simulation..
4. Inhibition Effect of Oyster Reef on Occurrence of Hypoxia in Ariake Sea.
5. 片野 俊也, 吉田 誠, 山口 創一, 吉野 健児, 濱田 孝治, 郡山 益美, 速水 祐一, Effect of nutrient concentration and salinity on diel vertical migration of Chattonella marina (Raphidophyceae), 10, 10, 1007-1018, 2014.05, Vertical migration plays an important role in the development of Chattonella populations in the natural environment;however, this behaviour has remained largely undescribed. In the present study, the diel vertical migration of Chattonella marina in the Ariake Sea was examined along with nutrient concentrations and salinity at four sampling sites during the bloom in the summers of 2008, 2009 and 2010. Cells of Chattonella were abundant at the surface (0 m depth) in the daytime in most cases. However, when surface salinity was 9, which is the lower limit for growth, the population accumulated at a depth of 2 m, where salinity was 15, suggesting that Chattonella moves to avoid water with low salinity. Chattonella cells actively migrated, even under nutrient-replete conditions (mean DIN concentration, 12.73 μM). The present study demonstrates that Chattonella cell migration is independent of nutrient availability. In addition, Chattonella cells stop upward migration when the surface salinity is low (< 15). These insights are important for making predictions of hattonella population dynamics after heavy rains. .
6. Prediction of the environmental impacts by the gate-opening of the Isahaya Bay reclamation reservoir with proposal of better gate control procedure.
7. Generation of Tidal Current Energy Map around Kyushu-Okinawa region.
8. Masumi Koriyama, Yuichi Hayami, Akane Koga, Koichi Yamamoto, Alim Isnasetyo, Takaharu Hamada, Kenji Yoshino, Toshiya Katano, Soichi Yamaguchi, Seasonal variations of water column nutrients in the inner area of Ariake Bay, Japan: the role of muddy sediments, 10.1007/s10661-013-3068-8, 2013.01, To investigate seasonal variations of nutrient distribution in the mudflat–shallow water system, we conducted field surveys once a month from August 2007 to July 2008 in the inner area of Ariake Bay (IAB), Japan. The NH4–N concentration of the water column increased in autumn because of the high NH4+ release from the sediments, ranging from 850 to 3,001 μmolm−2day−1. The NO3 −–N concentration was maximal in January, which was thought to be caused by NO3 − release from the oxic sediments and by NO3 − regeneration due to water column nitrification. The PO4 concentration of the water column was high in summer–autumn due to the high PO4 release from the reduced sediments, ranging from 22 to 164 μmolm−2day−1.We estimated the total amounts of DIN and PO4 release (RDIN and RPO4 , respectively) from the muddy sediment area of the IAB. In summer–autumn, RDIN and RPO4 corresponded to about 47.7 % of DIN input and about 116.6% of PO4 3−–P input from the river, respectively. Thus, we concluded that the muddy sediments were an important source of nutrients for the water column of the IAB during summer–autumn. In addition, we found that phosphorus necessary for the growth of Porphyra (Porphyra yezoensis, Rhodophyceae) would be insufficient in the water column when phosphorus during the Porphyra aquaculture period is supplied only from the river. Therefore, the phosphorus release from the muddy sediments was thought to play an important role in the sustainable production of Porphyra in Ariake Bay..
9. Numerical Simulation of Sediment Transport in Ariake Bay
10. Generation Mechanism of Upwelling current with “Aoshio” occurrence in summer of 2008 in Ariake Sea.
11. Toshiya Katano, Makoto Yoshida, Souichi Yamaguchi, Takaharu Hamada, Kenji Yoshino, and Yuichi Hayami, Diel vertical migration and cell division of bloom-forming dinoflagellate Akashiwo sanguinea in the Ariake Sea, Japan
, Plankton and Benthos Research, in press, 2011.01.
12. Seasonal and Temporal Variation in Flow off Chikugo River Mouth in the Inner Part of Ariake Sea.
13. Generation Mechanism of Hypoxia in Isahaya Bay.
14. Behavior of low salinity water and its implication for the water quality after freshets at the head of the Ariake Sea.
15. Soichi Yamaguchi and Yusaku Kyozuka, A NUMERICAL SIMULATION OF PHYSICAL ENVIRONMENTS IN THE ARIAKE SEA INCLUDING THE EFFECTS OF THE TIDAL FLAT, 22nd International Conference on Offshore Mechanics and Arctic Engineering, 2003.06.