摘要
为探究散粒加糙床面对逆坡明渠流速分布的影响,采用粒子图像测速(PIV)技术开展了正、逆坡明渠非均匀流水槽试验,对比分析纵向间距比(糙元纵向间距(λ_(x))与糙元高度(h)之比)在2~16范围内的主流流速分布与近床区流场结构,并揭示了理论床面位移(z_(0)/h)和等效粗糙高度(k_(s)/h)的变化规律。结果表明:①双平均(时间-空间平均)流速分布在糙元上方呈对数,且近水面流速随坡度由逆转正而增大;糙元下方则呈线性分布。②在λ_(x)/h=2时,正坡因空腔回流显著降低近床流速,逆坡工况无回流,减速效果较弱;当λ_(x)/h≥4时,正、逆坡工况均出现1.1h~1.4h的分离区。③z_(0)/h随糙元间距增大呈对数减小,随坡度由逆转正而增大。④k_(s)/h在λ_(x)/h=4时达到峰值,且随坡度由逆转正显著增大。研究成果可为调水工程输水能力优化提供理论支撑。
To explore the influence of spacing-roughened beds on velocity distribution in adverse-slope open channels,flume experiments under nonuniform flow conditions employing particle image velocimetry(PIV)were conducted.These experiments encompassed both positive and adverse slopes.A meticulous comparative analysis was performed on the mainstream velocity distribution and the structure of the near-bed flow field for various longitudinal spacing ratios(the ratio of longitudinal spacing λ_(x)to the height h of roughness elements),spanning from 2 to 16.Additionally,the variations in the zero-plane displacement z_(0)/h and the equivalent roughness height k_(s)/h were explored.The results show that:①The doubleaveraged(time-space averaged)velocity distribution tends towards a logarithmic distribution above roughness elements,with near-surface velocity escalating as the slope transitions from adverse to positive.Below the roughness elements,the profile exhibits a linear distribution.②Specifically,at λ_(x)/h=2,the positive-slope case scenario displays a significant reduction in near-bed velocity due to cavity recirculation.Conversely,the adverse-slope situation showcases no recirculation,resulting in a weaker velocity reduction effect.For λ_(x)/h≥4,separation zones of 1.1h to 1.4h emerge in both positive-and adverseslope instances.③The zero-plane displacement z_(0)/h diminishes logarithmically with augmented roughness spacing and intensifies as the slope transitions from adverse to positive.④The k_(s)/h peak_(s)at λ_(x)/h=4 and undergoes a significant increase when the slope changes from adverse to positive.These findings offer valuable theoretical underpinnings for enhancing the conveyance capacity of water diversion projects.
作者
袁康
张涛涛
肖洋
刘佳明
YUAN Kang;ZHANG Taotao;XIAO Yang;LIU Jiaming(School of Environmental Science and Engineering,Suzhou University of Science and Technology,Suzhou 215009,China;College of Water Conservancy and Hydropower Engineering,Hohai University,Nanjing 210098,China;Key Laboratory of Water Cycle and Hydrodynamic System,Ministry of Water Resources,Hohai University,Nanjing 210098,China;National Key Laboratory of Water Disaster Defense,Hohai University,Nanjing 210098,China;College of Harbour,Coastal and Offshore Engineering,Hohai University,Nanjing 210098,China)
出处
《水科学进展》
北大核心
2025年第5期882-894,共13页
Advances in Water Science
基金
国家自然科学基金项目(U2240209,52309102)。
关键词
逆坡明渠流
非均匀流
散粒加糙床面
流速特性
床面坡度
adverse-slope open-channel flows
nonuniform flows
spacing-roughed bed
velocity characteristics
bed slope
