1995 Fiscal Year Final Research Report Summary
Study on Tidal Exchange in Brackish Lake
| Project/Area Number |
06650561
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
水工水理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
IMAMOTO Hirotake Kyoto Univ., D.P.R.I., Protessor, 防災研究所, 教授 (20025943)
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| Co-Investigator(Kenkyū-buntansha) |
MUTO Yasunori Kyoto Univ., D.P.R.I., Research Associate, 防災研究所, 助手 (40263157)
ISHIGAKI Taisuke Kyoto Univ., D.P.R.I., Associate Professor, 防災研究所, 助教授 (70144392)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Brackish Lake / Tidal Exchange / Tidal Currents / Field Observation / Hydraulic Model Test / Numerical Simulation |
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| Research Abstract |
To investigate the tidal exchanging process in a brackish lake, we chose Kumihama Bay as a research field. Kumihama Bay, located in the northern part of Kyoto prefecture, Japan, has its area of 7km2 and the mean depth of 10m. The bay is connected by a 30m wide and 700m long channel on its north side to the Sea of Japan and has characteristics of both brackish lake and semi-enclosed basin.
Three kinds of investigation method, that is hydraulic model tests, numerical simulations and field observations, were performed in order to clarify the currents in the bay. A model of the bay was constructed according to the Froude similarity law, of which scales are 1/1000 in horizontal and 1/200 in vertical. A unique tracer method was used to visualize both surface and internal flow in the model. 2-D depth averaged numerical model was used to calculate the velocity distribution in the model. The solution follows an iterative procedure based on the ADI scheme. The field observations using float tracing method were undertaken in Aug. and Nov.1994.Measurements of velocity, salinity and water temperature were also carried out.
Main results are as follows :
1) The experimental results show two distinctive flow features. One is that circulating flow exists in the region near the entrance to the channel. The other is that the velocity in the southern part of the bay is very small ;
2) The internal flow behavior in the model is similar to that on the surface. 2-D numerical model can simulate well the experimental results ;
3) Fundamental flow characteristics in the area dominated by tidal currents show good agreement between the experimental and field data. However in the southern part where the tidal effect is not dominant, two-layred stratified flow was observed in the field.
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