沉水植物对水流及底泥再悬浮特性影响研究

发布时间：2018-02-15 08:21

本文关键词： 沉水植物水流特性底泥再悬浮弗汝德数　出处：《长江科学院》2014年硕士论文　论文类型：学位论文

【摘要】：河道中的沉水植物能够有效降解水体中的污染物质、防止水土流失，起到美化环境、固滩固岸的作用。但沉水植物改变了原有河道的水流结构及底泥再悬浮特性，使河道水力学问题变得更为复杂。前人对含沉水植物河道的水流及底泥特性进行了研究并取得了较多的成果，但采用天然的沉水植物开展试验研究的并不多见，对这种特殊而复杂的水流问题进行深入研究很有必要，研究成果对指导开展河道生态修复及环境保护等工作有着重要的现实意义。本文在收集整理国内外有关含植物河道水流特性研究成果的基础上，采用天然的沉水植物-苦草在水槽中进行了系列模拟试验，利用先进的三维声学多普勒流速仪(ADV)对不同工况下的水流参数进行了测量，采用自制微扰动虹吸采样器取水样，利用浊度仪器测量试验水槽上覆水浊度的变化，取得了大量宝贵的第一手资料。对比分析了无沉水植物和含沉水植物以及沉水植物在不同种植方式下对水流及底泥再悬浮特性的影响规律。研究成果表明：（1）沉水植物明显改变种植区的水流流速及紊动特性，减小河道底部切应力；上覆水浊度变化值亦表明试验条件下沉水植物可一定程度上抑制河道底泥再悬浮。（2)横向种植间距对水流特性影响明显，间距越小，近底流速减速效应越明显，更有利于减小底部水流紊动效应，抑制底泥再悬浮；纵向种植间距对水流特性影响程度不及横向间距，但沉水植物段上覆水浊度随纵向种植间距增大仍有所增大，，这表明纵向种植间距对底泥再悬浮也有一定的影响。 (3)随着弗汝德数的增大，种植沉水植物前后流速分布曲线差异性增大；不同弗汝德数条件下，紊动强度最大值、紊动能最大值、雷诺应力最大值的大多数位于植物顶部附近；种植密度增大，可明显降低底部紊动能和底部切应力，对底泥再悬浮的抑制效果较明显。
[Abstract]:Submerged plants in river channels can effectively degrade pollutants in water bodies, prevent soil and water loss, beautify the environment and stabilize banks and banks. However, submerged plants have changed the flow structure of the original river channels and the characteristics of sediment resuspension. The problems of river channel hydraulics have become more complicated. Many researches have been made on the characteristics of water flow and sediment in river channels containing submerged plants, but few experiments have been carried out by natural submerged plants. It is necessary to study this special and complex water flow problem, and the research results have important practical significance to guide the work of river ecological restoration and environmental protection. On the basis of collecting and arranging the domestic and foreign research results on the flow characteristics of vegetated river channels, a series of simulation experiments were carried out in the flume by using natural submerged plant-bitter grass. The parameters of water flow under different working conditions were measured by using the advanced three-dimensional acoustic Doppler velocimeter (ADV). The water samples were taken by self-made micro-disturbance siphon sampler, and the turbidity change of the overlying water on the test flume was measured by turbidimetric instrument. A great deal of valuable firsthand data have been obtained. The effects of submerged plants, submerged plants and submerged plants on the characteristics of water flow and sediment resuspension under different planting methods have been compared and analyzed. The results of the study indicate that:. 1) the submerged plants can obviously change the flow velocity and turbulent characteristics of the growing area and reduce the shear stress at the bottom of the channel, and the change of turbidity of overlying water also indicates that the submerged plants can restrain the resuspension of the river sediment to a certain extent under the experimental conditions. (2) the lateral planting spacing has obvious influence on the flow characteristics, the smaller the spacing, the more obvious the deceleration effect of the near bottom velocity, which is more favorable to reduce the turbulent effect of the bottom water flow and restrain the resuspension of the sediment. The influence of longitudinal planting spacing on water flow characteristics is not as great as that of transverse spacing, but the turbidity of overlying water on submerged plant segments increases with the increase of longitudinal planting spacing, which indicates that longitudinal planting spacing also has a certain effect on sediment resuspension. (3) with the increase of Froude number, the difference of velocity distribution curve increases before and after planting submerged plants, the maximum turbulence intensity, the maximum turbulent energy and the maximum Reynolds stress are located near the top of the plant under different Froude numbers. With the increase of planting density, the turbulent energy and shear stress at the bottom can be obviously reduced, and the inhibition effect on the resuspension of sediment is obvious.
【学位授予单位】：长江科学院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV133;TV14

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