植物对明渠流速分布影响的试验研究

Experimental study on the influence of vegetationon the velocity distribution of open channel flows

采用圆柱铝棒模拟刚性植物进行水槽试验,利用激光流速仪LDV对含非淹没、淹没植物明渠流场进行了测量,对模拟植物淹没度、密度对流速分布的影响进行了研究.分析表明,植物非淹没条件下的平均流速可以表示为流量、渠宽、水深和植物密度的函数;植物淹没条件下,很难用统一的函数描述平均流速沿水深的分布,植物层上部和内部与顶部处的流速偏离有随淹没度、密度的增大而增大的规律,相同宽深比条件下,含淹没植物明渠和无植物明渠相比,最大流速位置前者高于后者,植物"抬高床面"或是减小了有效宽深比的作用.

Vegetation is an important feature of natural rivers. Based on the flume experiments with aluminum cylinders simulating rigid vegetation and the laser Doppler velocimetry, the influences of vegetation submergence and density on the velocity distribution are investigated in this study. The analyses indicate that the mean streamwise velocity can be expressed by a function of flow discharge, channel width, water depth and vegetation density for non-submerged vegetated flows. For submerged cases, it is difficult to find a function to express the velocity distribution change with the whole water depth. The velocity deviation between both the upper layer and vegetation layer and the vegetation top become larger with the increment of vegetation submergence and density. The location of the maximum velocity of submerged vegetated flow is higher than that of non-vegetated flow with the same aspect ratio. The vegetation enhances the ＂bed level＂ or reduces the ＂effective aspect ratio＂ of channel.