摘要
床面粗糙特性是河流动力学中的重要研究内容,其量化方法一直是研究的难点。在顺直水槽中采用非均匀天然沙铺制初始床面,并逐渐增大流量粗化床面,基于激光扫描获得的床面数字高程资料,应用统计理论以及变异函数模型探讨不同粗化程度的床面表层粗糙特性。结果表明:采用非均匀沙人工铺制的床面高程频率分布呈现出近似正态分布,经历过不同水流强度依次累积冲刷后形成的稳定粗化床面高程频率分布都出现了轻微正偏态的趋势;高程标准差随水流强度增加严格增大的特点让它可以成为量化床面粗糙特性的可靠指标;水流塑造试验床面是各向异性的,随着流量的增大,床面粗化层破坏再粗化,床面高程二维变异函数的基台值越大;由于水流的作用,横向剖面平均变异函数的基台值与块金值略大于纵向剖面高程平均变异函数,径向剖面的基台值与块金值远小于横向与纵向剖面。研究加深了对床面粗糙特性的统计规律的探索,对于建立基于统计学的粗糙度定量表达方式具有一定的启示。
Riverbed roughness is an important aspect of river dynamics research,and its quantitative measurement has always been challenging.In this experiment,regardless of the macroscopic undulation of the riverbed,we laid the initial bed surface in a straight channel with non-uniform natural sand and thickened it by gradually increasing the flow rate of water.Laser scanning technology was used to obtain highresolution bed elevation data after each bed roughening.Statistical theory and variogram function were used to investigate the surface roughness characteristics of riverbeds with varying degrees of coarseness,and to deepen the understanding of their statistical characteristics.The study′s main finding is that artificially laid non-uniform sand presents an elevation frequency distribution that approximates a normal distribution.On the contrary,the frequency distribution of the stable rough bed surface formed by the continuous cumulative erosion of different flow intensities shows a slight positive deviation trend.The study found evidence that the increase of flow intensity leads strictly to an associated elevation standard deviation increase.This finding indicates that elevation standard deviation can be used as a reliable indicator to measure the characteristics of riverbed roughness in future studies.The study revealed that the kurtosis of the bed elevation data precisely decreased monotonically with the flow intensity,and that skewness and kurtosis showed a monotonic trend,indicating that they can be used to measure bed roughness.Additionally,the study found that the flow forming the bed surface is anisotropic,and as flow intensity increases,the rough layer breaks and becomes rougher again.This leads to an increase in the base value of the two-dimensional bed elevation variogram.Therefore,the study suggests that the base value of the two-dimensional variogram could serve as another reliable index for evaluating bed surface roughness.In addition,due to the influence of water flow,although the change trend of the characteristic parameters of the average variogram along the flow direction,vertical flow direction and radial profile elevation is consistent,the average variogram base value and golden point value of the transverse section are slightly larger than those of the transverse and longitudinal sections.Conversely,in the radial section,the abutment value and nugget value are considerably smaller than the values in transverse and longitudinal sections.In conclusion,this study enhances our understanding of the characteristics of bed roughness and provides crucial insights into statistical expressions for quantifying it.
作者
林星宇
蔡暾
杨克君
LIN Xing-yu;CAI Tun;YANG Ke-jun(State Key Laboratory of Hydraulics and Mountain River Engineering,Sichuan University,Chengdu 610065,Sichuan Province,China;Power China Chengdu Engineering Corporation Limited,Chengdu 610072,Sichuan Province,China)
出处
《中国农村水利水电》
北大核心
2023年第10期1-8,共8页
China Rural Water and Hydropower
基金
国家自然科学基金资助项目(51979181)。
关键词
床面粗糙特性
统计参数
变异函数
球状模型
bed surface roughness
Statistical parameters
Variation function
spherical mode
