| Budget Amount *help |
¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1987: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
In the last year, which ended March 1990, I performed the actual observations, analysis of the new data, and an analysis of the results combined with all data from the past. The observations began on schedule at the Teshio River in the first part of August. However, unfortunately, the weather deteriorated due to a typhoon in the Japan Sea at the time, and Hokkaido was grazed by a low pressure area. Because of the high winds and high waves, we were not able to observe normal two-layer flow. Accordingly, it was impossible to obtain measurements of Reynolds stress in ideal two-layer flow. As the measurements of this year were not performed to satisfaction, we plan to presume this year, and plan to publish a report in 1991. However,, we have obtained following results of major significance in our studies of macroscale problems.
The two parameters K and F_d which control fluctuations with respect to physical dimensions and time have been definitively determined. Here K is a comparative index between the average depth at the river mouth and the amplitude of the tide while F_d is the Froude number of the dense flow. When data from observations both past and present is plotted on the K-F_d plane, the conditions governing direction of flow of the river and the occurrence of the three kinds of flow, and the limits of intrusion of salt water are clearly described.
During the final year of this program using nonlinear stability analysis, we clarified the growth of interfacial waves, a clue to the explanation of interfacial phenomena, to the weakly nonlinear stage. Results of the analysis showed that transformations in the interface were brought about by instabilities in the flows immediately above and below the interface, that these register as interfacial waves, and that the resulting theoretical streamline structure matches nearly perfectly with the observed one.
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