Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

Arturo S. Leon

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Hector R. Fuentes

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Dwayne McDaniel

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Arindam Gan Chowdhury

Fourth Advisor's Committee Title

Committee Member

Keywords

Air–water interface interactions, combined sewer overflow, combined sewer system, flows in pipes, geyser, OpenFOAM, sewer hydraulics, stormwater, violent eruption

Date of Defense

2-21-2023

Abstract

A sewer geyser in stormwater (SW) or an old combined sewer system (CSS) consists of multiple consecutive eruptions of a gas and liquid mixture that occur in dropshaft/vertical shafts (i.e., manholes). A sewer geyser in a storm sewer system is caused by heavy rainfall, which may lead to air entrapment and its subsequent release. The intensity of sewer geysers may vary; however, the resultant spillage from such events severely impacts public health, safety, and the environment. They can contaminate drinking water sources and potentially harm public health and the environment. Furthermore, the resulting damage to the infrastructure and property can be significant. The aim of this research is to comprehend the underlying mechanisms responsible for the occurrence of violent geysers in storm sewer systems, using field-scaled laboratory observations and computational fluid dynamics numerical models (2D and 3D). This study reports a detailed experimental procedure to produce sewer geysers resembling those observed in actual SW and CSSs, designed and investigated at Florida International University, Miami. Water and air were used as the test fluids. In this study, pressure transducers, a flow meter, a wire-mesh sensor, thermocouples, and a high-speed camera were used to record the pressure variation, flow rate, void fraction, temperature, and two-phase flow regime, respectively, using a data acquisition system. Extensive 3D numerical simulations were performed to ascertain the effects of the initial water depth and diameter of the dropshaft on the intensity of geyser eruptions. Numerical modeling, in conjunction with laboratory tests, improves our ability to understand violent sewer geysers mechanistically. For potential geyser mitigation, two near-surface strategies were proposed and evaluated numerically. The first strategy consists of a chamber with a larger diameter compared to the dropshaft, and the second strategy utilizes an orifice plate combined with an adjacent bypass. The results showed that the widened chamber releases the trapped air with a relatively low rise of the water column in the dropshaft, resulting in a less intense eruption. Although rapid accelerations were still present in the dropshaft section beneath the chamber, the enlarged chamber diminished the overall impact. Adding a bypass combined with an orifice plate to the dropshaft strategy failed to alleviate the rapid eruption and needed further modifications. Further experimental data is needed to gain a better understanding to validate and improve the effectiveness of these mitigation strategies.

Identifier

FIDC011063

Previously Published In

Zanje S. R., Mahyawansi P., Leon A. S., and Lin C. X. (2022). “CFD Modeling of Storm Sewer Geysers in Partially Filled Dropshafts.” In World Environmental and Water Resources Congress 2022, Atlanta, GA.

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