急弯河道壁面切应力及计算方法研究

发布时间：2018-06-25 15:42

本文选题：急弯 + 壁面切应力　；参考：《工程科学与技术》2017年02期

【摘要】：壁面切应力的准确计算对深入了解泥沙输运及河道演变过程非常重要。当前研究多局限于顺直和微弯河道,对于急弯河道,水流受重力和离心力的双重作用,流态复杂,水面横比降大,并伴随横向环流,壁面切应力影响因素众多,各种计算方法的适用性有待进一步研究。开展180°急弯水槽缓流试验,采用ADV流速仪以及Preston管监测水流的3维流速和动静水压强差分布,分析急弯河道水流纵向流速、横向环流以及湍动能重分布特征。基于以上水流特征,选取4种经验公式法及k-ε数值模拟法计算该水槽控制断面的壁面切应力,对比发现湍动能法、Preston管经验公式法以及k-ε数值模拟法的计算结果不仅在分布规律上,而且在数值大小上都吻合良好,可用于急弯河道壁面切应力的计算。利用数值模拟法计算该水槽内河床及岸坡的壁面切应力分布,结果表明:在进口顺直段内,壁面切应力值较小,且分布均匀,在弯道段内,其值逐渐增大,分布也更不均匀,进入出口顺直段后,岸坡附近的壁面切应力值达到最大;横向上壁面切应力沿底壁分布均匀,而在坡脚附近,水流条件复杂,环流作用大,波动剧烈;横断面最大壁面切应力在弯道作用下从凸岸逐渐偏移至凹岸,与主流变化规律一致;该急弯水槽最大壁面切应力位于弯道内110°断面的凸岸附近以及弯道出口下游0.5 m断面的凹岸附近;保持水槽出口水深不变,仅过水流量变化,壁面切应力总体分布规律相似,并体现出"大水趋直,小水坐弯"的特点。成果为急弯河道的水流剪切输移机理、河道演变预测及安全管理等研究提供基础依据。
[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 掳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 掳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.
【作者单位】：武汉大学水资源与水电工程科学国家重点实验室;中国电力工程顾问集团中南电力设计院有限公司;
【基金】：国家自然科学基金资助项目(11472198) 国家重点研发计划资助项目(2016YFC0402303)
【分类号】：TV147

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