【作者】 向珂； 杨中华； 刘建华； 方浩泽；

【Author】 XIANG Ke;YANG Zhong-hua;LIU Jian-hua;FANG Hao-ze;State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University;

【机构】 武汉大学水资源与水电工程国家重点实验室；

【摘要】 无论是人工丁坝群形成的滞水区(groin fields)还是自然河岸内陷形成的河湾(embayment),都与河道主流间存在混合交换层。明渠滞水区通常存在低速度环流结构,可以为水生生物提供有利的生存条件,是生物生长的重要区域。尽管前人对侧空腔区域的水动力学进行了深入研究,但植被条件下滞水区的相关研究相对较少。本研究采用大涡模拟(LES)研究了植被种群密度变化下矩形滞水区的紊动水流结构,用物理模型实验测得的时均流场对数值模型进行了验证。发现植被的存在影响了滞水区的环形结构,削弱了流速和湍动能,这种负面影响随着种群密度的增加而加强。伴随着交界面前缘诱导的脱落涡的发展,大尺度相干结构在混合层形成,这种拟序结构的发展几乎不受种群密度变化的影响。分析了植被化滞水区的水体滞留时间,发现随着种群密度增大,平均滞留时间先减小后增大,该现象是由大尺度相干结构、植株诱导的卡门涡街以及植被群阻滞效应3个因素共同作用的。更多还原

【Abstract】 Both the groin fields formed by the artificial consecutive groynes and the embayment formed by the natural indention of the river banks,have a mixing layer with the river mainstream,and there generally existing a circulation structure with a low level of velocity in the lateral cavity(called dead-water zone).Dead-water zones in the open channel can provide favorable growing conditions for aquatic organisms,and is an important area for biological growth.Although flow hydrodynamics in the lateral cavity have been well studied,the impact of vegetation on recirculating flow is rarely considered.This study adopts large eddy simulation(LES) to examine the turbulent flow structure in a rectangular embayment zone with different population densities of vegetation,and the numerical model is validated by the the physical experiment.Vegetation rearranges the circulation structure in the DWZ and weakens the velocity and turbulent kinetic energy.This negative effect increases with increasing population density.With the development of the shedding vortex induced in the front edge of the channel-embayment interface,the large-scale coherent structure forms in the mixing layer and is hardly affected by the variation of population density.As the vegetation density increases,the mean retention time first decreases and then increases as a result of the combined action of three factors,namely,the large-scale coherent structure,the plant-induced Karman vortex street,and the blocking effect of dense vegetation.更多还原