Geyser Eruptions and Hydraulic Transients

Violent geysers can result from the uncontrolled release of air through vertical shafts. These explosive geysers are extremely destructive and pose significant operational risks. To prevent such events, many municipalities operate their combined sewer systems (CSSs) well below maximum capacity. However, this conservative approach leads to more frequent combined sewer overflows (CSOs), which remain a major water pollution issue in approximately 772 cities across the United States.

Dr. Arturo Leon, our technical consultant, specializes in transient flow modeling and has led pioneering work in this field. His research focuses on developing advanced mathematical and numerical models to simulate transient free-surface flows, pressurized flows, and mixed flow regimes involving both air and water (two-phase interactions). Dr. Leon led the development of the state-of-the-art Illinois Transient Model (ITM), a tool now widely used for both transient and steady-state analysis of combined sewer systems. ITM has been adopted by major U.S. cities—including Chicago, Cleveland, Pittsburgh, San Francisco, and Dallas—as well as internationally in countries such as Switzerland, France, Germany, and New Zealand.

Experiments on Violent Air-Water Geyser Eruptions ?

Dr. Arturo Leon has successfully reproduced violent air–water geyser eruptions in a laboratory setting for the first time. These experiments produced a series of consecutive eruptions—typically three to eight—within just a few seconds, reaching heights of over 30 meters. The behavior and characteristics of these laboratory geysers closely resemble those observed in real-world stormwater and combined sewer systems. A video of one of Dr. Leon’s geyser flow experiments can be viewed here. The images below capture snapshots from several of his groundbreaking experiments.

Snapshots of maximum eruption heights for four of Dr. Leon's geyser experiments

Sequential snapshots of geyser eruption in one of Dr. Leon's experiments

Sequential snapshots in the horizontal pipe of one of Dr. Leon's geyser experiments

Snapshots of Dr. Leon's numerical simulations produced with OpenFoam

Transient Flows in Urban Systems

Dr. Arturo Leon has conducted extensive research on transient flows in urban water systems. His work includes investigations into the effects of gate closures on the formation of hydraulic transients in combined sewer systems, the potential for surge formation in closed-conduit systems, and the simultaneous occurrence of free-surface and pressurized flows within these systems. He has also studied the complex filling processes of reservoirs in combined sewer systems—ranging from dry-bed and free-surface flows to mixed and fully pressurized conditions.

To support his research, Dr. Leon has employed a combination of computational fluid dynamics (CFD) modeling, laboratory experimentation, and his proprietary Illinois Transient Model (ITM). This advanced modeling tool is used globally to analyze flow dynamics in both stormwater and combined sewer systems.

Snapshots of some of Dr. Leon's transient flow simulations/measurements