Solute Transport Modeling for Urban Drainage Structures

Solute transport and dispersion processes affect the performance of a wide range of water engineering structures. Some urban drainage network models transport the pollutants by advection only, whereas others also account for the effects of dispersion, although there is only limited knowledge regarding appropriate values for dispersion parameters. Computational fluid dynamics (CFD)-based software tools enable engineers to simulate flow patterns and associated pollutant transport mechanisms within both natural and engineered hydraulic structures. It is feasible to use CFD to represent solute transport using two contrasting approaches, an unsteady species (scalar) transport model or a discrete phase (Lagrangian particle tracking) model. This paper outlines these two approaches, using the example of a storage tank to demonstrate, compare, and validate the two approaches, and to explore a number of issues associated with interpretation of the simulation outputs. It is concluded that both CFD-based approaches may be usefully utilized for the design and modeling of urban drainage systems.