Effect of Weir Face Angles on Circular-Crested Weir Flow

The standard circular-crested weir is often found in engineering applications and is used as a discharge measurement device or as an overflow structure. This research determines the discharge coefficients for ten circular-crested weir configurations with various combinations of up-and downstream angles. Two different weir heights and four different overflow depths are considered for each weir shape. For free overflow, the discharge coefficient is determined experimentally by using the total head of the approach flow. The results indicate that the upstream weir face angle has only a small effect on the discharge coefficient. In contrast, increasing the downstream weir face angle increases the discharge coefficient notably. A new formula for the discharge coefficient is presented, including both the up-and downstream weir face angles. Further, the hydraulic performance of the circular-crested weir, the resulting discharge reduction from tailwater submergence, and transition flow are discussed. DOI: 10.1061/(ASCE)HY.1943-7900.0000346. (C) 2011 American Society of Civil Engineers.