Discussion on weir flow coefficient for broad-crest ridge-free weirs

The broad crest ridge free weir is a common structural form of hydraulic structures. In determination of the size of sluice projects, the influence of weir flow coefficient should not be ignored. For convenient and precise determination of the flow coefficient for broad crest ridge free weirs according to the compulsive requirement of the current trade standard, a discussion is made on the adoption of the calculating formula, conforming to "the sluice design specifications" SL265 2001, to derive a suitable value of the flow coefficient for further calculation of the discharge capacity and determination of scale of sluice projects by a comparative analysis of data from hydraulic model tests on some completed hydraulic projects. It is concluded that the flow coefficient in the range of 0.36～0.375 is suitable for broad crest ridge free weirs with a rectangular conjunctive section between the upper and lower reaches of lock chambers under free outflow conditions.