Transport Phenomena at Intersections of Pressurized Pipe Systems

Abstract

The movement of chemicals or biological agents in a water distribution system is examined via computational fluid dynamics simulations. A series of computational simulations using selected intersecting geometries are carried out at various Reynolds numbers. Boundary conditions, turbulence intensities, convergence criteria, and mesh sizes are thoroughly evaluated. The present parametric study focuses particularly on pipe intersections to characterize complex mixing phenomena in pressurized water distribution pipe networks. Selected computational results are compared with experimental results. The water quality model integrated with an existing computer program (EPANET) was re-evaluated based on the computational and experimental data. Initial computational fluid dynamics simulations consistently underestimated mixing, and experimental data are utilized to reexamine turbulent mixing by adjusting the turbulent Schmidt number. Corrections based on computational results are incorporated into the existing code as an example case study. The improvement of the existing code may be important not only to predict concentrations of chemical species such as chlorine in water distribution systems, but also to prepare for potential intentional and accidental contamination events. Computational results must be further calibrated and verified through lab- and field-scale experiments. This paper was presented at the 8th Annual Water Distribution Systems Analysis Symposium which was held with the generous support of Awwa Research Foundation (AwwaRF).