基于分形理论的漂浮植被水流垂线流速分布研究  

Study on vertical distribution of velocity in floating vegetation flow based on fractal theory

作　　者：耿颖颖 张皎 李占斌[1] 王添[1] Ying-ying Geng;Jiao Zhang;Zhan-bin Li;Tian Wang(State Key Laboratory of Eco-Hydraulics in Northwest Arid Region,Xi'an University of Technology,Xi'an 710048,China)

机构地区：[1]西安理工大学省部共建西北旱区生态水利国家重点实验室,西安710048

出　　处：《水动力学研究与进展（A辑）》2022年第4期441-451,共11页Chinese Journal of Hydrodynamics

基　　金：国家自然科学基金(U2040208;52109100;52009104);中国博士后科学基金面上资助(2021M702643)。

摘　　要：漂浮植被可以为水生生物提供生存空间,同时其覆盖在水面可抑制藻类生长,其根系还可以吸附并降解水中的污染物起到净化水体的作用,因此漂浮植被对天然河道的生态修复具有重大意义。漂浮植被通过改变水流垂线流速分布情况,进而影响水流中污染物的输移和泥沙的输运等。因此,漂浮植被水流中的垂线流速分布是至关重要且值得研究的。该文将漂浮植被水流流速垂线分布分为河床区和植被区,利用分形理论研究其分形特征。基于分形标度律,得到浮毯型漂浮植被水流中不同形式的垂线流速分布表达式;基于双对数表达式对试验数据拟合,证明了浮毯型漂浮植被水流在植被区和河床区均具有分形现象,而浮叶型漂浮植被水流的垂线流速分布不具有分形现象;利用分形维数对植被区和河床区流速分布进行分析,发现分形维数越大,流速分布越均匀。Floating vegetation can provide living space for aquatic organisms,and inhibit algae growth while it covers the water surface.In addition,its root system can absorb and then degrade pollutants in the water to play the role of purifying waterbodies.Hence,floating vegetation is of great significance for the ecological restoration of natural rivers.Though changing the vertical distribution of the flow velocity,the floating vegetation affects the transport of pollutants,sediment and so on.Therefore,the vertical distribution of velocity in the flow covered by the floating vegetation is worth studying.In this paper,the vertical distribution of flow velocity is vertically divided into riverbed zone and vegetation zone,and fractal characteristics in each zone are studied by fractal theory.Based on the fractal scaling-law,various expression for the vertical distribution of velocity in flow covered by the floating vegetation with undeveloped roots is obtained,and by fitting the experimental data based on two logarithmic expression,it is proved that the flow covered by the floating vegetation with undeveloped roots in vegetation zone and riverbed zone owns fractal characteristics,while the vertical distribution of flow velocity in the flow covered by the floating vegetation with developed roots does not show any fractal characteristics.The fractal dimension is used to analyze the velocity distribution in the vegetation and river bed zones,and it is found that the fractal dimension is proportional to the uniformity of the velocity distribution.

关 键 词：漂浮植被 流速垂线分布 分形标度律 分形维数 分形理论 

分 类 号：TV133[水利工程—水力学及河流动力学]