低坝影响下的流场与淤积形态特性试验研究

Experimental study on flow and sedimentation characteristics under the effects of low-head,run-of-river dams

为研究径流式低坝影响下的水流流动与泥沙淤积特性,开展水槽试验,基于图像测量技术,获取并解析坝附近区域流场信息及典型淤积形态。结果表明:坝前附近流段纵向流速在垂线上出现衰减区,减幅随水流强度增大而减小;坝顶断面纵向和垂向流速沿垂线的分布均呈现显著的分区特性,分区界限几乎不受水流强度的影响;随坝顶水深增加,坝下游漩涡涡心向下游及河底移动,面积和强度皆增大;坝上游淤积形态特性对水流强度的变化非常敏感,在较低强度来流下,呈接近坝体的稳定曲面斜坡,而在高强度来流下,不形成稳定淤积体;坝下游形成动态稳定的淤积斜坡,纵剖表面线呈抛物线规律,随来流强度变异程度小。

Flume experiments were carried out to investigate the flow and sedimentation characteristics under the effects of run-of-river dams.Based on an image measuring technique,the flow field and sedimentation characteristics were analyzed.It was observed that the longitudinal velocity of the cross-sections behind the dam had an attenuation zone on the vertical line,which decreased when there was an increase in the flow intensity.The distribution of longitudinal and vertical velocity along the vertical line of the dam crest cross-section presented significant zoning characteristics,and the zoning boundaries were almost unaffected by the flow intensity.When water depth increased at the crest of the dam,the vortex center,in the downstream of the dam,moved towards downstream and river bed,and both its area and intensity increased.The characteristics of the sedimentation morphology were very sensitive to changes in the flow intensity.At low-intensity flow,the slope of sedimentation was close to the dam body,while at high-intensity flow,no stable sedimentation was formed finally.A dynamic and stable slope entailed sedimentation in the downstream of the dam.Due to the strong vortex at the dam downstream,dynamically stable sedimentations maintain therein,and their surface profiles approximately follow the parabola law with no observable variations among different flow conditions considered here.