Effect of Channel Slope on Energy Dissipation of Flow for Single Step Broad–Crested Weirs

Abstract

The effect of channel bed slope on energy dissipation of flow for single step Broad– Crested Weir was studied experimentally under free flow conditions. Five weir models were manufactured and tested , and one hundred twenty one experiments were conducted in a laboratory horizontal channel of 12m length, 0.5m width and 0.45m depth for a wide range of discharge. The experimental results showed that water surface profiles were smooth and continuous and had a descending trend from the point of measurement taking the shape of the weir with a steep drop near the downstream face of the weir. It was found that for the same ratio (P/P1) the channel slope effect (S) was inversely proportional on the energy dissipation. In addition, the effect of (He/P) did not appear when (P/P1 =1&1.2), while in the other weirs appeared. An empirical non-dimensional relation was obtained to determine the energy dissipation ratio in terms (He/p), (P/P1), (S) and (Fr2) with high correlation coefficient.