Water Displacement in Shafts and Geysering Created by Uncontrolled Air Pocket Releases

• Published in: Journal of hydraulic engineering (New York, N.Y.) Vol. 143; no. 10
• Main Authors: Muller, Kathleen Z, Wang, Jue, Vasconcelos, Jose G
• Format: Journal Article
• Language: English
• Published: American Society of Civil Engineers 01-10-2017
• Subjects: Technical Papers
• ISSN: 0733-9429; 1943-7900
• DOI: 10.1061/(ASCE)HY.1943-7900.0001362

AbstractUncontrolled air pocket release from water-filled shafts can lead to geysering in stormwater systems. Such occurrences are deleterious from public health and environmental standpoints and can cause property and structural damage. Causes, frequency, magnitude, and location of geysering events still are poorly understood and pose practical difficulties to designers regarding how to create dropshafts that are less likely to present this issue. This paper presents results from experimental and numerical investigations on air-related geysers that provide insight into the mechanisms of air release and the displacement of water in vertical shafts. A 302-mm schedule 40 clear PVC apparatus is constructed with the essential features of a stormwater tunnel, and is fitted with vertical shafts with diameters ranging from 0.10 to 0.20 m. Predetermined air pocket volumes are released in the horizontal pipe and eventually reach shafts, causing water displacement and often causing geysers. Kinematics of the air pocket release are measured along with pressures at selected points in the apparatus. These results are used in the calibration of a computational fluid dynamics (CFD) model, which compares well with the experimental measurements. The model subsequently is used in a larger geometry that allows the evaluation of air pocket release kinematics for a wider range of conditions. Findings of this work provide further details on the nature and strength of geysering events, and suggestions for future studies in this topic are also provided.