Comparison of gully flow due to different gully outlets

The hydraulic performance of an urban drainage system depends on the surface and the sewer network and also on their linking elements. Gullies and manholes are the two most common elements in an urban drainage system. Gullies collect runoff from roadside curbs and conveys it to the buried drainage system through the manhole. In a flood routing model, accurate prediction of discharge capacity of a gully is important as it decides the amount of flow between surface and underground drainage network. Different types of gully outlets may have different discharge capacities due to its size and positioning; which often ignored in preparing a flood routing model. This work focuses on simulating numerically the hydraulic performance of a gully, sizing 0.6 m × 0.24 m × 0.32 m (L × W × D) connected below a 0.5 m wide rectangular channel and draining to a manhole of 1 m diameter. The numerical simulation uses OpenFOAM® CFD modelling toolbox with the solver interFoam that includes Volume of Fluid (VOF) method. The CFD model is validated physical model simulation data from Dual Drainage Multiple Linking Element experimental installation located at the Laboratory of Hydraulics of the University of Coimbra. The model is used to investigate flow hydraulics, flow efficiency and discharge coefficient of the gully for different gully outlet pipes. Results will also be examined for different slopes of the outlet pipe.