Propagation of Surcharge Conditions in Flowing Sewers

Previous experimental investigations on the issue of flow regime transition from free surface to pressurized flow in stormwater sewers have introduced extreme conditions to generate pipe-filling bore fronts. These conditions include the admission of large inflow into still water conditions and sudden flow blockage in a pipeline. It is unclear whether the results of these experiments are representative for flow regime transition events in actual flowing sewers. This paper summarizes an experimental investigation in which pipe-filling bore fronts were generated by introducing large inflows in sewers initially in flowing conditions with drawdown profiles due to a free overfall at the downstream end. This condition is perceived as a more representative scenario in which flow regime transition events would occur. Pressure and velocity measurements were performed and the results compared well with predictions from a flow regime transition model.