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  本文關鍵詞： 沉水植物 水流特性 底泥再懸浮 弗汝德數　出處：《長江科學院》2014年碩士論文　論文類型：學位論文

【摘要】：河道中的沉水植物能夠有效降解水體中的污染物質、防止水土流失，起到美化環(huán)境、固灘固岸的作用。但沉水植物改變了原有河道的水流結構及底泥再懸浮特性，使河道水力學問題變得更為復雜。前人對含沉水植物河道的水流及底泥特性進行了研究并取得了較多的成果，但采用天然的沉水植物開展試驗研究的并不多見，對這種特殊而復雜的水流問題進行深入研究很有必要，研究成果對指導開展河道生態(tài)修復及環(huán)境保護等工作有著重要的現實意義。 本文在收集整理國內外有關含植物河道水流特性研究成果的基礎上，采用天然的沉水植物-苦草在水槽中進行了系列模擬試驗，利用先進的三維聲學多普勒流速儀(ADV)對不同工況下的水流參數進行了測量，采用自制微擾動虹吸采樣器取水樣，利用濁度儀器測量試驗水槽上覆水濁度的變化，取得了大量寶貴的第一手資料。對比分析了無沉水植物和含沉水植物以及沉水植物在不同種植方式下對水流及底泥再懸浮特性的影響規(guī)律。 研究成果表明： （1）沉水植物明顯改變種植區(qū)的水流流速及紊動特性，減小河道底部切應力；上覆水濁度變化值亦表明試驗條件下沉水植物可一定程度上抑制河道底泥再懸浮。 （2)橫向種植間距對水流特性影響明顯，間距越小，近底流速減速效應越明顯，更有利于減小底部水流紊動效應，抑制底泥再懸浮；縱向種植間距對水流特性影響程度不及橫向間距，但沉水植物段上覆水濁度隨縱向種植間距增大仍有所增大，，這表明縱向種植間距對底泥再懸浮也有一定的影響。 (3)隨著弗汝德數的增大，種植沉水植物前后流速分布曲線差異性增大；不同弗汝德數條件下，紊動強度最大值、紊動能最大值、雷諾應力最大值的大多數位于植物頂部附近；種植密度增大，可明顯降低底部紊動能和底部切應力，對底泥再懸浮的抑制效果較明顯。
[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.
【學位授予單位】：長江科學院
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TV133;TV14

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