Preliminary Assessment of a Retrofit Strategy in Dropshafts Impacted by Geysering Using CFD

The operational issues created by episodes of storm water geysering have drawn researchers and engineers’ attentions in the past 20 years. However, only recently that more insights has been obtained in the geysering events caused by uncontrolled release of trapped air pockets in a water-filled vertical shaft. With better understanding upon the key factors affecting geyser intensity, it is possible to determine practical ways to mitigate negative effects of air release, which leads to geysering. This manuscript evaluates in a preliminary fashion the strategy of extending the lower rim of vertical shafts to the springline of horizontal tunnels/sewers as a means to reduce the capture/scooping of air pockets that travels in these conduits as gravity currents. The strategy is evaluated for a simple geometry by applying the CFD tool OpenFOAM to model the passage and interaction of the air pocket with the vertical structure of the extended shaft. Different configurations with different shaft geometries are simulated and compared with conditions in which these extensions are not used. The results will guide the development of experiments that will evaluate this strategy in a laboratorial setup.