在中小型堰、闸、跌水等渠系建筑物中,其下游的水流衔接和消能一般均采用底流式。但是,由于建筑物水头不高,常在低弗汝德数(Froude)的情况下运行,故消能效果不理想。当弗汝德数为10～40时,水跃消能率只有28～59%。又因底流消能的主流在渠底部,对渠槽冲刷较大,且底流消能的消力池较长, In medium and small weir, gate, water fall and other canal buildings, the downstream convergence and energy dissipation are generally used underflow. However, due to the low head of the building, it is often operated with a low Froude number, so the energy dissipation is not satisfactory. When the Froude number is 10 ~ 40, the water jump energy dissipation rate is only 28 ~ 59%. And because of the mainstream of mainstream energy dissipation at the bottom of the channel, scouring the channel larger, and the end of the energy dissipation pool is longer,