1991 Fiscal Year Final Research Report Summary
Buoyancy Effects on Hydrodynamics of Semi-Enclosed Bay
| Project/Area Number |
02302067
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | Osaka Sangyo University |
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Principal Investigator |
MUROTA Akira Osaka Sangyo University, Department of Civil Engineering, Professor, 工学部, 教授 (50028924)
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| Co-Investigator(Kenkyū-buntansha) |
OOKUBO Kenji Kyoto University, Disaster Prevention Research Institute, Research Associate, 防災研究所, 助手 (50135612)
OONISHI Sotoaki Tokyo Science Univ., Department of Civil Engineering, Professor, 理工学部, 教授 (20103062)
MICHIOKU Kohji Kobe University, Department of Civil Engineering, Associate Professor, 工学部, 助教授 (40127303)
MURAOKA Kohji Osaka University, Department of Civil Engineering, Professor, 工学部, 教授 (90029017)
NAKATSUJI Keiji Osaka University, Department of Civil Engineering, Associate Professor, 工学部, 助教授 (10029324)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Stratified flow / Semi-enclosed Sea / Front / Water exchange / Tidal flow system / Wing-induced current / Water quality / Internal wave |
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| Research Abstract |
Four research meetings have been held during two years of the project term for promoting mutual understanding about the role of density-induced currents on the hydrodynamics of semi-enclosed bays, and discussing the following synthetical themes ; (a) the effects of external forces and geometries of semi-enclosed bay on the flow and density structure ; (b) the buoyancy effects on turbulent transport of momentum and passive water qualities such as temperature, salinity and turbidity ; and (c) individual subjects studied in individual coastal and estuarine waters by co-operative investigators. The results of individual subjects are as follows :
(l) Murota and Nakatsuji develop a three-dimensional baroclinic model for examining ther hydrodynamics of an estuarine front and a tidal front observed in Osaka Bay. The mutual effects of stratification, the earth's rotation and tidal modulation are clarified quantitatively.
(2) Fujiwara clearly shows the estuarine circulation in Osaka, Bay on the ba
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sis of many field observations. Taking note of stratification structure in the narrow entranced embayments such as Osaka Bay, the constant current system is classified depending on the induced forces ; tidally-induces and buoyancy-induced residual currents.
(3) Muraoka and Nakatsuji analyze hydrodynamically field data of temperature and velocity fluctuations which were measured related with the upwelling phenomena of 'Aoshio' (anoxic water) often observed in Tokyo Bay. A two-dimensional experiments are performed to clarify the mechanism of upwelling and mixing of two-layered stratified flow system exposed to wind stresses at the surface.
(4) Murakami carries out hydraulic experiments for examining the effects of geometrically-induced horizontal circulation and buoyancyinduced vertical circulation on the water exchange when the breakwater is constructed at the mouth of enclosed bay.
Furthermore, the numerical experiments were performed for clarifying the dependency of numerical schemes such as layer model and level model on the resulting difference in the computed vertical circulation.
(5) Oonishi develops a system for the analysis of river effluent spreading using satellite data. Effluent from the Singuu River are analyzed as an example to study the difference in the dispersion areas detected by water temperature and water turbidity.
(6) Ookubo measured temperature fluctuations due to the interfacial waves in a shallow North Lake in Australia within the range between the internal wave of buoyancy frequency and the surface wind ripple and evaluate the vertical eddy viscosity coefficient under the influence of stratification. These results are compared with observation results obtained in the south water of Biwa Lake.
(7) Michioku measured temperature and velocity fluctuations in Nunobiki Reservoir, Kobe and analyzed the relationship between their fluctuations and meteorological factors such as wind and temperature. The flow structure and mixing process in a stratified reservoir are clarified. Less
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