X型宽尾墩阶梯掺气空腔影响因素分析

Affect Factors Analysis of Aerated Cavity of X-shaped Flaring Gate Pier

X型宽尾墩+阶梯联合消能工已被应用于实际工程。当第一级阶梯高于其它阶梯时,水舌底部与阶梯之间存在气腔,从而水流底部实现掺气,在单宽流量超过30 m3/(s.m)时阶梯可避免空蚀危害。研究了气腔尺度与堰上水头、堰顶至宽尾墩出口高程差、挑坎高度、堰面末端坡度、阶梯坡度之间的关系,并导出气腔长度的计算公式,计算结果与模拟及试验数据比较吻合。研究结果表明,除了水力要素外,阶梯坡度、堰面末端坡度与挑坎高度是气腔形成的关键原因,也是影响气腔大小的主要因素。

A step spillway placed behind X-shaped flaring gate pier was proposed and applied in practical engineering. If the first step is higher than the others, cavity will exist between the nappe and the step spillway. The flow with air entrainment will occur on the flow surface of steps. Under this condition, the step can be protected from damage at the discharge over 30 m^3/（ s·m）. The relation of the cavity size, the weir head, the difference between the weir crest and the exit of the flaring gate pier, the drop height, the weir end slope and the step slope were studied in this paper. The formula was deduced to calculate the length of cavity. Calculating results were identical with that of numerical stimulations and experiments. It is shown that the cavity is mainly affected by the drop height, the weir end slope and the step slope.