跌坎深度对扩散式泄槽底流消能水力特性影响试验研究

Experimental Study on the Influence of Falling-sill Depth on the Hydraulic Characteristics of Bottom Flow Energy Dissipator in Diffusion Chute

对于高水头泄水建筑物而言,为了降低出口单宽流量,减轻下游消能压力,通常在出口设置扩散式泄槽。突扩式底流消力池增设跌坎,可避免水流直接冲击消力池底板,降低底板力学指标。通过水工模型试验,基于一定的边墙突扩宽度,研究突扩式消力池在不同跌坎深度下底板临底流速、时均压强、脉动压强的变化。成果表明:跌坎深度为5cm时,消力池内水流流态介于临界水跃向远驱式水跃过渡区间,临底流速最大,时均压强最小;跌坎深度增加至10cm时,消力池能够形成稳定的淹没水跃,临底流速明显减小,时均压强明显升高;跌坎深度进一步增加至15cm时,消力池内淹没程度继续增加,临底流速继续减小,时均压强继续增加,但变幅均不大。

For high head discharge structures, in order to reduce the outlet discharge per unit width and the downstream energy dissipation pressure, the diffusion chutes are usually installed at the outlet. The installation of falling sills at sudden-expansion bottom flow stilling basin can avoid the direct impact of water flow on the stilling basin floor and reduce the mechanical index of the floor. Based on a certain sudden-expansion width of side wall, this paper studies the changes of underflow velocity, time-averaged pressure and fluctuating pressure of sudden-expansion stilling basin under different falling-sill depth through hydraulic model test. The results show that when the falling-sill depth is 5 cm, the flow pattern in stilling basin is at the transition zone from critical hydraulic jump to repelled downstream hydraulic jump, the underflow velocity is the largest, and the time-averaged pressure is the smallest;when the stilling-sill depth increases to 10 cm, the stilling basin can form a stable submerged hydraulic jump, the underflow velocity decreases obviously, and the time-averaged pressure increases obviously;and when the falling-sill depth is further increased to 15 cm, the degree of submergence in stilling basin continues to increase, the underflow velocity continues to decrease, and the time-averaged pressure continues to increase, but the variation is not significant.