Study on the Development of the Tidal Dam in Oder to Prevent the Oxygen-Deficiency in an Enclosed Bay

为了防止半封闭海湾的滞流，减少半封闭海湾分层季节氧气底水的减少，提出了一种称为潮汐坝的新技术。简单结构的设计是为了通过产生分层海水的垂直循环来改善水质环境。本研究包括潮汐坝水力参数的理论和实验研究以及实际海域的水质改善现场试验。在前一部分中，通过水力学和数值试验研究了该装置的原理、基本结构设计、基本水力参数、引射管喷流卷吸强度以及几何尺寸的确定方法。在后半部分，利用在乌拉努奇湾建造的小型原型进行了现场试验。上述水力模型和大坝OP…的有效性验证了对底水水质环境的更多污染。并对实际应用中可能出现的问题进行了探讨。研究取得的重要成果如下：1)本模型能较准确地估算大坝水库与海湾之间管道的水力参数和喷流入海底的夹带率；2)乌拉努奇湾的潮差通常比邻近海域大，因此，只利用潮汐势能的潮汐坝是一种非常有效的水质改善措施；3)大坝运行增加了底层分层水中的溶解氧浓度，加速了有机底泥的分解过程；4)在现场试验过程中，坝库内可生活多种鱼类和贝类，可作为养鱼的场所，下一步应对该技术的底层水环境改善情况、防粘措施及经济效益进行定量分析。较少

In order to prevent the stagnation and to reduce the less oxygen bottom water in stratified seasons in a partly enclosed bay, a new technique, called the tide-dam, is suggested. The simple structure is designed to improve the water quality environment by generating the vertical circulation of the stratified sea water.The present study consists of the theoretical and experimental investigations on the hydraulic parameters of the tide-dam and the field experiments on the water quality improvement in an actual sea. In the former part, the principle of this idea, its basic structural design, the fundamental hydraulic parameters, the entrainment intensity of jet flows from ejecting pipes, and the way to determine the geometrical dimensions of this facility are investigated by hydraulic and numerical experiments. In the later part, the field experiments were carried out using the small scale prototype constructed in Uranouchi Bay. The above hydraulic model and the effectiveness of the dam op … More eration on the bottom water quality environment were verified. And the problems which may occur in the practical use are examined. The important results obtained in these studies are as follows :1) the hydraulic parameters of pipelines connecting the dam reservoir with a bay and the entrainment rate due to jet flows into the sea bottom are accurately estimated by the present model ;2) the tidal range of Uranouchi Bay is usually larger than that of the adjacent open sea, therefore, the tide-dam which utilizes only the tidal potential energy is a quite effective measure for water quality improvement ;3) the dissolved oxygen concentration of the stratified bottom sea water increases by the dam operation, and the decomposition process of the organic bottom mud is accelerated ;4) the dam reservoir can be used as the fish nursery because many kinds of fishes and shellfishes can live in the dam reservoir during the field experiment.To turn this technique to practical use, the quantitative analysis of the improved environment of bottom sea water, the measure against adhesive organisms on the connecting pipes and the economic effect should be investigated as the next step. Less