切向进口段收缩比对跌水竖井模型水流流态转换的影响

Effect of Contraction Ratio of Tangential Inlet Section on Flow Pattern Transformation in Drop Shaft Model

跌水旋流竖井是排水系统中将泄水从高处输送至低处的一种常用结构形式,其切向进口段收缩宽度设计会影响竖井内部水流的流态特征,在不同泄流流量条件下,产生跌流流态与旋流流态间的转化。采用跌水旋流竖井模型试验测量并分析了不同流量与切向进口宽度条件下竖井内泄流能力、流态、压力分布等水力特性。结果表明,随着切向进口段收缩比的减小,竖井内泄流流态逐渐由跌流转变为贴壁旋流运动形式,水流流量的增大,有利于在大收缩比条件下形成竖井旋流流态;基于竖井壁面压力分布的差异,以竖井进口断面时均压力最小值与最大值之比作为判别跌流与旋流流态的水力指标。

The drop shaft is a common structural form in which the discharge water is transported from high to low in the drainage system. The design of the contraction width of the tangential inlet section will affect the flow pattern characteristics of the flow in the drop shaft, resulting in the transformation between the drop flow pattern and the swirling flow pattern under different discharge flow conditions. In this study, the hydraulic characteristics such as discharge capacity, flow pattern and pressure distribution in the drop shaft under different discharge and tangential inlet width were measured. The experimental results show that with the decrease of the contraction ratio of the tangential inlet section, the discharge flow pattern in the drop shaft gradually changes from dropping flow to swirling flow, and the increase of discharge is conducive to the formation of swirling flow pattern in the drop shaft under the condition of large contraction ratio. Based on the difference of pressure distribution on the wall of drop shaft, the ratio of the minimum and maximum time average pressure of the inlet section was chosen as the hydraulic index to distinguish the flow pattern of dropping and swirling flow.