Flow over Submerged Sharp-Crested Compound Weirs: A Momentum–Balance-Based Approach

Abstract In some applications, compound weirs are implemented as adjustable structures that create additional resistance locally to help divert flow in rivers. To ensure proper functioning, the added resistance needs to be implemented into numerical river hydrodynamic models, which are typically constructed with 1D or 2D coarse meshes. Therefore, their effects should be defined through a simple formula to enable implementation as subgrid energy losses. This study employed an experimental approach to estimate the flow resistance of submerged compound weirs under varying flow rates and configurations. A 1D analytical method based on momentum balance at the downstream side of the weir was proposed, with a correction term included to account for neglected factors. The modeled and measured results were in strong alignment for almost all 54 cases. A uniform weir configuration with the largest weir area required a higher correction coefficient for accurate predictions. Performance testing of the model on a variety of literature data shows that this method can be applied to various kinds of weirs.