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Hydraulic characteristics in vegetated open channel flows.

植被明渠水流的水力特性。

基本信息

批准号：
05660279
负责人：
KATO Osamu
金额：
$ 1.34万
依托单位：
SAGA University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

The objectives of this study are to investigate the effects of the sway of flexible standing roughness elements on the profiles of mean velocity, turbulence intensities and Reynolds stress, and to develop a theoretical model which can explain the experimental results.A relationship between the deflection of reeds and water velocity was investigated in order to understand the physical characteristice of reeds, e.g.flexural rigidity.The reeds as the roughness elements were used Hydrilla verticillata(L.f).Casp.KUROMO and Potamogeton oxyphyllus Miquel, YANAGIMO.The experiments were conducted in a recirculating open channel 7.0m long, 0.4m wide, and 0.4m deep. The roughness elements were placed in a bed 0.9m long with the same distance in a between in a square lattice. For each roughness, the experiment was divided to three cases.In this model, the momentum equations are derived for the steady uniform flow and the displacement of roughness elements is analyzed as the static deflection problem of cantilever, in which the hydrodynamic force is converted into the external force acting on the roughness elements. The flow field may be conveniently separated into two region ; (1)the outer region, which corresponds to the region above roughness elements, (2)the inner region, which corresponds to the region within roughness elements.The analytical velocity profile show that the theory could bu used efficiently to predict the characteristics of flow.The hydrodynamic force acting on one roughness element is assumed to be proportional to the projected area in the flow-direction and to the square of mean velocity, and the displacement of roughness elements is derived from the bending moment at an arbitrary position.The calculated deflection of the roughness element agree to all of the experimental profiles with exception of the case of slow velocities.

本文研究了柔性直立粗糙元件的摆动对平均流速、湍流强度和雷诺应力的影响，并建立了一个能解释实验结果的理论模型。试验采用黑藻（Hydrilavertricillata（L.f）.Casp.KUROMO）和尖叶眼子菜（Potamogeton oxyphyllus Miquel，YANAGIMO）的芦苇作为糙率元件，在长7.0m、宽0.4m、深0.4m的循环明渠中进行。粗糙度元件放置在0.9m长的床上，在正方形网格中具有相同的距离。对于每种粗糙度，实验分为三种情况，在该模型中，推导了恒定均匀流的动量方程，并将粗糙元的位移分析为悬臂梁的静挠度问题，将水动力转化为作用在粗糙元上的外力。流场可以方便地分成两个区域;（1）外部区域，其对应于粗糙元件上方的区域，（2）内部区域，本文提出了一种新的粗糙元模型，该模型的基本原理是将粗糙元的水动力作用在粗糙元上，并将粗糙元的水动力作用在粗糙元上，使粗糙元的水动力作用在粗糙元上粗糙元的挠度由任意位置处的弯矩导出，除低速情况外，计算的粗糙元挠度与所有的实验曲线相吻合。