Abstract:

Flow velocity and energy dissipation head are important hydraulic parameters in open channel flows. However, there is no systematic research achievement about it in stepped spillways so far. In this paper the concepts of relative flow velocity and relative energy dissipation head of stepped spillway were presented by comparing the velocity and energy dissipation head of stepped spillways with those of smooth spillways. Groups of tests were performed on stepped spillways with channel slope (38.66 °) and different step heights (0.5m, 1.0m and 2.0m). The measured data were analyzed and the results show that the relationship between flow velocity and energy dissipation head of non-uniform flow is complex, which is difficult to be applied, but the relative velocity of non-uniform flow has good linear relationship with relative energy dissipation head in the presence of different unit width discharges and step heights. The correlation coefficient is 0.973 7-0.995 9. The results prove the necessity of introducing the concepts of relative flow velocity and relative dissipation head for stepped spillways.

Key words: stepped spillway, relative flow velocity, relative energy dissipation head, smooth spillway, step height, non-uniform flow pattern