Numerical and Experimental Study on Mitigation of Storm Geysers in Edmonton, Alberta, Canada

Abstract

Geysers can occur in storm sewer systems during heavy storm events, leading to public safety concerns. In this study, a physical model as well as a transient three-dimensional computational fluid dynamic model were used to investigate potential mitigation methods. Two types of geysers, caused by the rapid filling and release of air pockets, were simulated numerically and validated with physical measurements. For geyser mitigation, benching, water recirculation chambers, and orifice plates were proposed and assessed numerically, and the effect of an inflow control method was also studied. The numerically tested geyser mitigation methods showed positive effects on reducing the amount of water erupting out of the manhole, but they also increased the amount of air transported downstream, which could cause issues further downstream. Water recirculation chambers mitigated the water erupting out of manholes without increasing the pressure in the pipes significantly. The strategy of sealing the riser was able to completely mitigate geyser events, but it also generated higher pressure in the upstream pipe and transported a higher amount of air downstream. It was found that using orifice plates to mitigate the second type geyser can generate a water hammer–like pressure pattern in the riser, with a peak pressure reaching about seven times the driving pressure when the orifice diameter is 0.2 times the riser diameter. With the inflow control method, the physically measured pressure variation was reduced, and the onset of geysers was visually reduced.