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工程科学与技术:2017,49(2):45-53
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急弯河道壁面切应力及计算方法研究
(1.武汉大学 水资源与水电工程科学国家重点实验室, 湖北 武汉 430072;2.中国电力工程顾问集团中南电力设计院有限公司, 湖北 武汉 430071)
Calculation Method of Boundary Shear Stress in a Sharply-curved Channel
(1.State Key Lab. of Resources and Hydropower Eng. Sci., Wuhan Univ., Wuhan 430072, China;2.Central Southern China Electric Power Design Inst. (CSEPDI) of China Power Eng. Consulting Group Co., Wuhan 430071, China)
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投稿时间:2016-03-14    修订日期:2016-12-13
中文摘要: 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。
中文关键词: 急弯  壁面切应力  Preston管  湍动能  k-ε模型
Abstract:The accurate calculation of boundary shear stress is very important to the deep understanding of sediment transportation and river evolution.The current research is limited to straight and mildly curved channels,while for a sharply-curved channel,the flow is complex accompanied by transverse circulation and large transverse slope which was affected by the dual effect of gravity and centrifugal force.As the boundary shear stress was affected by many factors,the applicability of differentcalculation methods requires further study.The distribution of three-dimensional flow velocity and dynamic-staticpressure difference were monitored by ADV as well as Preston tube in a 180°;sharply-curved flume under the subcritical flow condition.The typical features of transverse flow circulation,redistribution of longitudinal flow velocity and turbulence kinetic energy were analyzed.Based on the analyses,four empirical formulae and k-ε model were selected to calculate the boundary shear stress on the control section of the flume.The computational results of turbulence kinetic energy method and Preston tube method agree well with the k-ε numerical simulation not only in distribution pattern but also in magnitude.Therefore,the above three methods are feasible for the calculation of boundary shear stress in a sharply-curved channel.The boundary shear stress in bed and bank slope of the whole flume was calculated by numerical simulation.The results show that the value of boundary shear stress is small and evenly distributed in thestraight section following the flow entrance,then gradually increases and exhibits non-uniformity in the bending section. Finally it reaches the maximum near the bank slope in the straight section in front of the outlet.On the transverse section,the boundary shear stress is well distributed along the bed while strongly fluctuated near the toe of slope in which the flow is complex with large circulation.Under the effect of the bend,the maximum boundary shear stress in the transverse section gradually shifted from convex bank to concave bank,in order to keep up with the mainstream.The maximal boundary shear stress of the flume is located in the convex bank of 110°; cross-section of the bend and the concave bank of the cross-section 0.5 m downstream off the bend outlet.By changing the rate of flow but keeping the downstream water depth constent,the overall distribution of the boundary shear stress is similar and shows the characteristic of strong water flow along straight line while weak water flow along curve line.These researches provided support for flow shear transport mechanism,forecast of river evolution and safety management in the sharply-curved channel.
文章编号:201600226     中图分类号:    文献标志码:
基金项目: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)
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引用文本:
向媛,余明辉,魏红艳,余飞.急弯河道壁面切应力及计算方法研究[J].工程科学与技术,2017,49(2):45-53.
XIANG Yuan,YU Minghui,WEI Hongyan,YU Fei.Calculation Method of Boundary Shear Stress in a Sharply-curved Channel[J].Advanced Engineering Sciences,2017,49(2):45-53.