本文選題：急彎 + 壁面切應(yīng)力　； 參考：《工程科學(xué)與技術(shù)》2017年02期

【摘要】：壁面切應(yīng)力的準確計算對深入了解泥沙輸運及河道演變過程非常重要。當前研究多局限于順直和微彎河道,對于急彎河道,水流受重力和離心力的雙重作用,流態(tài)復(fù)雜,水面橫比降大,并伴隨橫向環(huán)流,壁面切應(yīng)力影響因素眾多,各種計算方法的適用性有待進一步研究。開展180°急彎水槽緩流試驗,采用ADV流速儀以及Preston管監(jiān)測水流的3維流速和動靜水壓強差分布,分析急彎河道水流縱向流速、橫向環(huán)流以及湍動能重分布特征。基于以上水流特征,選取4種經(jīng)驗公式法及k-ε數(shù)值模擬法計算該水槽控制斷面的壁面切應(yīng)力,對比發(fā)現(xiàn)湍動能法、Preston管經(jīng)驗公式法以及k-ε數(shù)值模擬法的計算結(jié)果不僅在分布規(guī)律上,而且在數(shù)值大小上都吻合良好,可用于急彎河道壁面切應(yīng)力的計算。利用數(shù)值模擬法計算該水槽內(nèi)河床及岸坡的壁面切應(yīng)力分布,結(jié)果表明:在進口順直段內(nèi),壁面切應(yīng)力值較小,且分布均勻,在彎道段內(nèi),其值逐漸增大,分布也更不均勻,進入出口順直段后,岸坡附近的壁面切應(yīng)力值達到最大;橫向上壁面切應(yīng)力沿底壁分布均勻,而在坡腳附近,水流條件復(fù)雜,環(huán)流作用大,波動劇烈;橫斷面最大壁面切應(yīng)力在彎道作用下從凸岸逐漸偏移至凹岸,與主流變化規(guī)律一致;該急彎水槽最大壁面切應(yīng)力位于彎道內(nèi)110°斷面的凸岸附近以及彎道出口下游0.5 m斷面的凹岸附近;保持水槽出口水深不變,僅過水流量變化,壁面切應(yīng)力總體分布規(guī)律相似,并體現(xiàn)出"大水趨直,小水坐彎"的特點。成果為急彎河道的水流剪切輸移機理、河道演變預(yù)測及安全管理等研究提供基礎(chǔ)依據(jù)。
[Abstract]:Accurate calculation of wall shear stress is very important for understanding sediment transport and river channel evolution. Most of the current studies are confined to the straight and slightly curved river channels. For the sharp curved rivers, the flow is complicated by gravity and centrifugal force, and the ratio of the water surface to the side decreases greatly, and with the lateral circulation, there are many factors that affect the wall shear stress. The applicability of various calculation methods needs further study. The slow flow test of 180 擄sharp bend flume was carried out. ADV velocity meter and Preston tube were used to monitor the distribution of three dimensional velocity and pressure difference between static and static water, and the characteristics of longitudinal velocity, transverse circulation and turbulent kinetic energy redistribution were analyzed. Based on the above characteristics of water flow, four empirical formulas and k- 蔚 numerical simulation method are selected to calculate the wall shear stress of the control section of the flume. It is found that the calculation results of the turbulent kinetic energy method, Preston tube empirical formula method and k- 蔚 numerical simulation method are in good agreement not only in the distribution law but also in the numerical value, which can be used to calculate the shear stress on the wall of the sharply curved channel. The numerical simulation method is used to calculate the wall shear stress distribution of the river bed and bank slope in the flume. The results show that the wall shear stress value is smaller and more uniform in the inlet straight section, and in the bend section, the value increases gradually and the distribution is more uneven. After entering the straight section of the exit, the wall shear stress near the bank slope reaches the maximum value, and the lateral wall shear stress distributes evenly along the bottom wall, while near the foot of the slope, the water flow conditions are complex, the circulation is large and the fluctuation is intense. The maximum wall shear stress of the cross section is gradually shifted from the convex bank to the concave bank under the action of the bend, which is consistent with the mainstream variation rule. The maximum wall shear stress is located near the convex bank of 110 擄section in the bend and the concave bank of the 0.5 m section downstream of the bend outlet. And reflects the "big water straight, small water sitting bend" characteristics. The results provide the basis for the research on the mechanism of shear transport, prediction of channel evolution and safety management.
【作者單位】： 武漢大學(xué)水資源與水電工程科學(xué)國家重點實驗室;中國電力工程顧問集團中南電力設(shè)計院有限公司;
【基金】：國家自然科學(xué)基金資助項目(11472198) 國家重點研發(fā)計劃資助項目(2016YFC0402303)
【分類號】：TV147

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