Experimental Study on Edmonton’s Storm Geyser Formation Mechanism and Mitigation Measures

• Author / Creator

  Liu,Lujia

• Uncontrolled air movement and release in drainage systems can lead to geyser events, which are defined as the air-water mixture explosively jetting out of manholes. As geysers are always explosive in nature, its occurrence can cause public safety concerns and property damages. Due to the complexity of air-water two-phase flow, the understanding of geyser occurrences is still inadequate, and retrofitting methods are still controversial for field application. This study aims at revealing the mechanism of geyser events and assessing potential geyser mitigation methods that are applicable in the field by conducting laboratory experiments.
  To address the geyser occurring in the manhole at the intersection of Gateway Boulevard and 30th Ave., Edmonton, Alberta, a conceptual and simplified scale model of roughly 1:20 was constructed in the T. Blench Hydraulic Lab at the University of Alberta. Eight series of experiments were designed based on the possible combinations of flow conditions in the upstream and downstream pipes. Among them, three series focused on the mechanism of geyser formation, and the other five focused on the potential geyser mitigation methods.
  The experiments on the geyser mechanism show that geyser can be triggered by two ways: the rapidly filling flow and the air release from the entrapped air pocket. After a suddenly further opening of a ball valve, a rapidly filling surge occurs in the upstream pipe and propagates downstream. If the water level in the downstream pipe is high, this rapidly filling flow can fill the chamber quickly and then shoot out of riser to form a single-shoot geyser. When the entire system is pressurized with an entrapped air pocket in the upstream pipe with a stagnant water column in the riser, a suddenly further opening of a valve will induces two phase of geyser events: the first phase is caused by the transient pressure, with one to two geysers, and the second is caused by the air releasing from the air pocket and the geyser event, which could include several independent geysers and last much longer than the first phase.
  For the possible geyser mitigation methods, a completely sealed riser top, an orifice plate installed at the riser top, in the middle of riser span and at the riser bottom, a water recirculation chamber (WRC) and an enlarged riser were tested and assessed. A much slow opening of the ball valve was also investigated. The results show that the orifice plate (OP) with a small orifice can greatly decrease the pressure peak in the system and the water amount of water out of the riser, but it will cause most of the air being transported downstream. Also, the water-hammer pressure is observed in cases with an orifice size of 0.2 times of the riser diameter. The water recirculation chamber (WRC) has a minor effect on the pressure in the system and either no geyser is observed or few drops of water come out from the riser. The enlarged riser increases the water amount out of the riser.
  Findings of this research could extend the knowledge from two aspects: (1) the details of geyser occurrence, and (2) possible mitigation methods on geyser events.

• Subjects / Keywords

  • Geyser formation
  • Geyser mitigation

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R30R9MK98

• License

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