Flow through a small pond outlet structure was modeled using the 3D volume-of-fluid method . Turbulent effects were included using the K Omega SST model, and rough wall functions were used to model the regions near the solid-fluid interface. The purpose of the model was to develop a stage-discharge curve for the structure. The outlet structure includes a trash rack with horizontal bars, the hydraulic effects of which traditional 1D or 2D models cannot account for. The geometry of the structure was determined using a combination of build plans, LiDAR data, and field measurements. The results of the model were compared to the stage-discharge curve calculated using weir and orifice equations . Modeling of the flow was performed using the OpenFOAM InterFoam solver. When compared to the 3D model, the weir equations underestimated the flow, and the orifice equation overestimated the flow. The steady demonstrates a practical method to determine stage-discharge curves for hydraulic structures, including geometry generation and meshing. Possible ways to refine the stage-discharge calculation process using the weir and orifice equations for use on drop structures that include trash racks with horizontal bars is discussed. The effect of including roughness in the model domain was also investigated.
