Numerical investigation of the effect of geometric parameters on discharge coefficients for broad-crested weirs with sloped upstream and downstream faces

Abstract

Abstract Weirs are structures that are important for measuring flow and controlling water levels. Research has shown that the discharge coefficient is not constant and depends on the crest length, the height of the weir, the upstream head, and the upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficient (C d ) is investigated by numerical simulation. The current study present numerical simulation using the ANSYS FLUENT software. The total number of simulations is 432 which includes: 4 upstream slopes, 4 downstream slopes, 3 weir heights, 3 upstream heads (h 1) and 3 weir crest lengths. It was found that the downstream face slope has little effect on C d . For 0.1 < H 1/w < 0.4 by decreasing the upstream slope, C d increases, where H 1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the C d increases. For 0.16 < H 1/p < 2, as the length of the crest decreases, the C d increases. By comparing the numerical simulation results to physical measurements, multi-variable regression equations for estimating C d are presented. In addition to C d , extraction of other more detailed information such as water level profiles and velocity profiles at different locations is provided.

Keywords

• Broad-crested weir
• Discharge coefficient
• Flow measurement
• Computational fluid dynamics
• Numerical simulation