【摘要】：近底泥沙運(yùn)動(dòng)與床面附近的水流結(jié)構(gòu)密切相關(guān),精細(xì)研究不同水流與邊界條件下近底水流結(jié)構(gòu)空間、時(shí)間上的差異,對(duì)于揭示近底泥沙運(yùn)動(dòng)輸移復(fù)雜多變性規(guī)律具有更為直接有效的學(xué)術(shù)意義。本文通過開展系列水槽試驗(yàn),利用ADV測(cè)速及高速攝像技術(shù),精細(xì)采集了近壁區(qū)的流速及紊動(dòng)特征值,分條帶計(jì)量了推移質(zhì)輸移情況。通過對(duì)比橫向密布測(cè)點(diǎn)的流速結(jié)構(gòu)差異,剖析了近底流速時(shí)空分布的不同變化特點(diǎn)與兩側(cè)的流速結(jié)構(gòu)變異。基于輸沙分條帶量化觀測(cè)模式,得以對(duì)推移質(zhì)輸移的空間橫向分布特性進(jìn)行了細(xì)致的分析。此外通過流速測(cè)點(diǎn)與輸沙條帶時(shí)間、空間上的同步關(guān)聯(lián)分析,探討了探索兩者之間的關(guān)系,認(rèn)為水流的流速分布與其紊動(dòng)結(jié)構(gòu)影響推移質(zhì)輸移,其中脈動(dòng)強(qiáng)度的作用十分明顯。在本次水槽試驗(yàn)中,重點(diǎn)研究近底區(qū)域水沙運(yùn)動(dòng)特性及推移質(zhì)輸移的橫向分布規(guī)律。采用精密可變坡水槽設(shè)備進(jìn)行相關(guān)試驗(yàn),由ADV進(jìn)行實(shí)驗(yàn)斷面的流速測(cè)量;推移質(zhì)泥沙輸移的動(dòng)態(tài)輸移記錄由動(dòng)態(tài)量測(cè)裝置實(shí)時(shí)記錄。從動(dòng)態(tài)的輸沙過程采集和瞬時(shí)流速去分析近底水流結(jié)構(gòu)對(duì)推移質(zhì)輸移的影響。分析不同水流條件下的實(shí)驗(yàn)結(jié)果發(fā)現(xiàn),橫向輸沙量從中間條帶向兩邊條帶逐漸減少,大體呈現(xiàn)偏態(tài)分布;分析發(fā)現(xiàn)在水流的近底區(qū)域,其橫向流速的流速分布和紊動(dòng)強(qiáng)度對(duì)于輸沙的橫向分布會(huì)有較大的影響,并且明渠恒定流推移質(zhì)輸沙率和斷面流速的橫向分布是造成床面形態(tài)的原因。推移質(zhì)輸沙的橫向分布是泥沙運(yùn)動(dòng)力學(xué)中有待深入研究的關(guān)鍵問題之一,關(guān)于推移質(zhì)泥沙的輸移機(jī)理、影響因素、計(jì)算方法的研究還需要進(jìn)一步的探索。
[Abstract]:The near bottom sediment movement is closely related to the flow structure near the bed surface. The spatial and temporal differences of the near bottom flow structure under different flow and boundary conditions are studied in detail. It is of more direct and effective academic significance to reveal the complex variability of sediment movement and transport near the bottom. In this paper, a series of flume tests are carried out, ADV velocimeter and high-speed camera technology are used to collect the velocity and turbulent eigenvalues near the wall, and the bed load transport is measured in strips. By comparing the velocity structure difference of the transverse dense measuring point, the different variation characteristics of the temporal and spatial distribution of the velocity near the bottom and the variation of the velocity structure on both sides are analyzed. Based on the quantitative observation model of sediment transport strip, the spatial transverse distribution characteristics of push load transport are analyzed in detail. In addition, through the synchronous correlation analysis between the velocity measurement point and the time and space of the sediment transport strip, the relationship between the two is discussed. It is considered that the velocity distribution of the flow and its turbulent structure affect the transfer of the transfer material, in which the pulsating intensity plays a very obvious role. In this flume experiment, the movement characteristics of water and sediment near the bottom and the transverse distribution of push load transport are studied. The related tests are carried out by precision variable slope flume equipment, and the velocity measurement of the experimental section is carried out by ADV, and the dynamic transport record of bed load sediment transport is recorded in real time by the dynamic measuring device. The influence of near-bottom flow structure on push load transport is analyzed from dynamic sediment transport process collection and instantaneous velocity. The experimental results under different flow conditions show that the lateral sediment transport decreases gradually from the middle band to the two sides of the band, and shows a skewness distribution. It is found that the velocity distribution and turbulence intensity of the transverse velocity have a great influence on the transverse distribution of sediment transport near the bottom of the flow. The bed shape is caused by the constant flow load transport rate and the transverse distribution of cross section velocity in open channel. The transverse distribution of bed load sediment transport is one of the key problems to be further studied in sediment transport dynamics. The research on the transport mechanism, influencing factors and calculation methods of bed load sediment transport needs to be further explored.
【學(xué)位授予單位】：華北水利水電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TV142.2

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