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Time-Space Variations of Hydraulic Parameters and Mixing Processes at the Density interface of River Mouth Flows

河口流密度界面水力参数及混合过程的时空变化

基本信息

批准号：
62460158
负责人：
YOSHIDA Shizuo
金额：
$ 3.07万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-62460158/
关键词：
River mouth LDA Stratified flow Interfacial waves Salt wedge Measurement of turbulence Tidal flow Weak non-linear stability analysis 河口密度流大規模渦河川乱流流速分布二層密度流

项目摘要

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.

在截至1990年3月的最后一年，我进行了实际观测，分析了新数据，并结合过去的所有数据对结果进行了分析。8月上半月，在手潮川如期开始观测。但不幸的是，由于当时日本海有台风，天气恶化，北海道被低气压区擦过。由于强风和巨浪，我们无法观察到正常的双层流动。因此，在理想的两层流中不可能获得雷诺应力的测量。由于本年度的测量工作未能令人满意，我们计划在本年度进行假设，并计划在一九九一年发表报告。然而，我们在宏观问题的研究中获得了下列具有重要意义的结果：确定了控制涨落随物理尺寸和时间变化的两个参数K和F_d。K为河口平均水深与潮幅的比较指标，F_d为密流的佛汝德数。当把过去和现在的观测资料绘制在K-F_d平面上时，可以清楚地描述出控制河流流向和三种水流发生的条件，以及盐水入侵的限度。在本计划的最后一年，我们利用非线性稳定性分析，澄清了界面波的增长，这是解释界面现象的线索，到弱非线性阶段。分析结果表明，界面上的转换是由界面上、下流动的不稳定性引起的，这些不稳定性被记录为界面波，由此产生的理论流线结构与观测结果几乎完全吻合。