Numerical study on effects of chamber design and multi-inlet on storm geyser

Storm geysers increasingly occur in sewer systems under climate change and rapid urbanization. Mitigation measures are in great demand to avoid safety problems. In this study, three-dimensional computational fluid dynamics models of single-inlet and multi-inlet systems were established to investigate geysering induced by rapid filling and assess the effectiveness of potential mitigation methods. The modeling results suggest that increasing the capacity of the downstream pipe before the inflow front reaches the chamber can effectively reduce the maximum geyser pressure. The peak pressure can be significantly mitigated when the chamber size is designed with care and the drop height between the upstream and downstream pipes is reduced. A diversion deflector with air vents and an orifice plate at the riser top end can alleviate the maximum pressure by about 65% with about 75% of the entrapped air being released. The peak pressure during the geyser event in the multi-inlet model is less than that of a single-inlet model under the same total inflow condition, but more water can be released. HIGHLIGHTS A small drop height between the connecting pipes can effectively reduce the maximum pressure during rapid filling.; Mitigation measures including flow deflectors and orifice plates were studied to alleviate geyser intensity.; Intermittent air–water jets can be generated much more easily in a system with multiple inlets, and the peak pressure is generally small but more water can be released.