Predicting the Head-area Slopes of Circular Holes in Water Pipes

Abstract

Leak openings in water distribution system pipes are not static, but vary with pressure. These changes in area affect the way that leaks respond to changes in pressure, and are thus important for municipal engineers to understand. In this study, the behavior of round holes in pressurized pipes was investigated using finite element analysis (FEA), under the assumption of linear elastic behavior. It was found that the areas of the round holes vary as linear functions of pressure in the pipe. A sensitivity analysis was then carried out to investigate parameters that influence the head-area slope. The elastic modulus, internal pipe diameter and pipe wall thickness were found to be the most important parameters. Solid mechanics theory was used to develop an equation to predict the head-area slope m of round holes in pipes. Finally, the results were compared to the findings of an experimental study. The comparison showed that the head-area slopes for both the equation and the FEA were within or close to the 95% confidence intervals of the experimental study.