植物密度对明渠紊流拟序结构的影响研究  

Study on effect of vegetation density on coherent structure in vegetated open channel flows

作　　者：闫静[1] 余洋 唐立模[1] 鲁经宇 YAN Jing;YU Yang;TANG Limo;LU Jingyu(College of Water Conservancy and Hydropower Engineering,Hohai University,Nanjing 210098,Jiangsu,China)

机构地区：[1]河海大学水利水电学院,江苏南京210098

出　　处：《水利水电技术（中英文）》2021年第12期133-145,共13页Water Resources and Hydropower Engineering

基　　金：国家自然科学基金项目(51979084,51579079)。

摘　　要：河道中淹没植物顶部附近的大尺度涡结构,影响着水体中的动量和物质交换,从而导致泥沙和污染物输移发生变化。基于淹没刚性植物条件下的水槽试验,利用粒子图像测速技术(PIV)对五种植物密度条件下的流场进行测量,分别用象限分析法和伽利略分解法,研究密度对植物顶部附近的猝发及KH涡垂向几何尺度的影响。研究表明:在试验条件下,植物密度增大会增强植物顶部附近的剪切作用,缩窄植物层内外动量交换的范围,抑制极端清扫作用对植物内部的侵袭。同时KH涡涡量增强,位置抬升,KH涡的垂向尺度总体增大,在密度较小的两种工况(0.09和0.18)时KH涡的垂向尺度较为接近,其值约为75~86 mm;密度为0.36时约为105~115 mm;密度为0.72和1.44时较为接近,在淹没度为4时约为114 mm,在淹没度为5时约为135 mm。Large vortex around the canopy top in submerged vegetated flows affects the momentum and mass transfer in the water, resulting in changes of sediment and pollutant transport. Flume experiments of open channel with the presence of submerged rigid plants have been carried out and particle image velocimetry(PIV) is used to measure the flow field with five plant densities. Quadrant analysis and Galilean decomposition method are used to investigate the effects of vegetation density on bursting and vertical geometry scales of KH vortex. The experiment reveals that higher vegetation density can increase the shear stress at its top edge, which then narrows the range of momentum exchange and restrains the penetration of extreme sweeping events into the vegetation. Also, the vorticity of KH vortex is enhanced, and its position is upraised. The vertical scales of KH vortex generally increase with density. The values of vertical scales of KH vortex are close for the sparser density cases(0.09 and 0.18)and are about 75~86 mm, and are 105~115 mm when the density is 0.36. While the density becomes larger(0.72 and 1.44), the values are 114 mm and 135 mm when the submergence are 4 and 5 respectively.

关 键 词：植物密度 明渠紊流拟序结构 PIV 猝发 KH涡 水力特性 影响因素 

分 类 号：TV131.2[水利工程—水力学及河流动力学]