UNSTEADY FACTORS AFFECTING SALT DIFFUSION IN THE STRATIFIED FLOW SYSTEM AT A RIVER MOUTH

影响河口层流系统盐分扩散的不稳定因素

• 批准号: 04452231
• 负责人: YOSHIDA Shizuo
• 金额: $ 3.26万
• 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: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452231/
• 关键词: River Mouth; Stratified Flow; Two-Layr Flow; Salt Diffusion; Salt Wedge; Entrainment Coefficient; Interfacial Instability; 界面不安定; 多層流; 界面波

The problem of salt diffusion in highly stratified flows such as those found at the mouth of a river is vital to considerations of agriculture and fisheries. Placement and control of the gates governing extraction of fresh water from a river have become social issues. Previous research has assumed that these flows are steady, and has focussed on problems of shear instability in the vicinity of the interface and natural turbulence. The research described below has examined these flows from the practical standpoint of whether and to what extent unsteady factors such as atmospheric pressure, tide, river flowrate, and wind affect salt diffusion around the river mouth. Those results have been used to attempt to develop an expression for improving predictions of the salinity of the river surface at any given point and time.These studies have been carried out mainly in the lower basin of the Ishikari River, Hokkaido, which is typical of a highly stratified flow. Observations were carried out … More in the summers of 1992,1993 and 1994 for about two months each. The observation methods were improved year by year and enough qualitative and quantitative data have been taken to fulfilll the research goals described above. The results of our research are as follows :1) Wind is the dominant factor in the surface salinity of a river. 2) The average entrainment coefficient of the salt wedge is given by the following formula : E = 1.92 * 10^<-6>e^<0.405^^W> for 118m^3/sec, E =2.24*10^<-6>e^<0.281^^W> for 146m^3/sec 3) The process of diffusion of salt from the salt wedge to the surface of a river has been shown to be the following : Wind blows>waves are generated>the turbulence in the upper layr increases>the distribution of salt in the upper layr is rendered uniform>the density gradient around the interface increases>the salt diffusion across the interface increases>the surface salinity increases. 4) The time average profiles of the flow system are stable throughout almost the entirity of the stratified flow system. 5) The process of diffusion is accelerated by an increase in river flowrate, but the salinity of the river water flow itself decreases. 6) Bridge piers and protuberences in the river bottom cause great disruptions in the interface, but the effect of these disruptions on salt diffusion is localized. 7) In order to predict the present surface salinity at any location it is sufficient to have an hourly record of wind speed along the river course and the discharge rate. Less

盐在高度分层流中的扩散问题，如在河口处发现的问题，对农业和渔业的考虑是至关重要的。从河流中抽取淡水的闸门的设置和控制已成为社会问题。以前的研究假设这些流动是稳定的，并集中在界面附近的剪切不稳定性和自然湍流的问题。下文所述的研究从实际角度对这些水流进行了研究，即大气压力、潮汐、河流流速和风等不稳定因素是否以及在多大程度上影响河口周围的盐扩散。这些结果已被用来尝试开发一种表达式，以改善对任何给定点和时间的河流表面盐度的预测。这些研究主要在北海道石狩河的下游流域进行，该流域是典型的高度分层流。进行了观察， ...更多信息 在1992年、1993年和1994年的夏天，每次大约两个月。观测方法逐年改进，取得了足够的定性和定量数据，以实现上述研究目标。研究结果表明：（1）风是影响河流表层盐度的主导因素。2)盐楔的平均夹带系数由以下公式给出：<-6>对于118立方米/秒，E = 1.92 * 10^ e^&lt;0.405 ^^W&gt;;对于146立方米/秒，E =2.24*10^<-6>e^&lt;0.281 ^^W&gt; 3）盐从盐楔扩散到河流表面的过程如下：风吹&gt;产生波浪&gt;上层湍流增加&gt;上层盐分分布均匀&gt;界面附近密度梯度增大&gt;盐分沿界面扩散增大&gt;表面盐度增加。4)流动系统的时间平均剖面在几乎整个分层流动系统中是稳定的。5)扩散过程会因河水流量的增加而加速，但河水流量本身的盐度会降低。6)桥墩和河底的protuberance在界面上造成了很大的干扰，但这些干扰对盐扩散的影响是局部的。7)为了预测任何地点目前的表面盐度，每小时记录沿着河道的风速和排放率就足够了。少

项目成果

大谷守正・吉田静男・西田修三: "弱混合河川下流域における表層塩分濃度の決定要因" 土木学会北海道支部論文報告集. 50. 584-589 (1994)

Morimasa Otani、Shizuo Yoshida 和 Shuzo Nishida：“弱混合河流下游地表盐度浓度的决定因素”日本土木工程师学会北海道分会论文集 50. 584-589 (1994)。

C.P.Caulfield: "Secondary Instability and Three-Dimeusionalization in a Laboratory Accelerating shear Layer with V.D.D." Dyn.Atmos.Oceans. (Accepted).

C.P.Caulfield：“实验室用 V.D.D 加速剪切层的二次不稳定性和三维化”

吉田 静男・大谷 守正・田城 徽雄 西田 修三・八木 史郎: "河口二層流の表層塩分に与える風の効果" 水工学論文集. 37. (1993)

Shizuo Yoshida、Morimasa Otani、Takeo Tashiro、Shuzo Nishida、Shiro Yagi：“风对两层河口流表面盐度的影响”水利工程学报37。（1993）

吉田: "Multiple Instability of Laboratory Stratified Shear Layer" 水工学論文集. 37. 439-444 (1993)

吉田：“实验室分层剪切层的多重失稳”水利工程学报37。439-444（1993）。

C.P.Coulfield: "Secondary Iustability and Three-Dimeusionalization in a Laboratory Accelerating Shear Layer with Varying Dousity Differouces" Dyn.Atmos.Oceans. (accepted).

C.P.Coulfield：“具有不同密度差的实验室加速剪切层的二次稳定性和三维化”Dyn.Atmos.Oceans。