A transient 2-D water quality model for pipeline systems

This study develops a water quality model in a pipeline during transient conditions using a two-dimensional (2-D) approach including advection, diffusion, and reaction terms. More specifically, using a modifiedVardy-Hwang hydraulic model, a 2-D transient model for flow is coupled with a 2-D advection-diffusion-reaction model for chemical constituent concentration.A five-region turbulence model is used to compute turbulent shear stresses. Using a fixed grid method of characteristics, the hydraulic equations are integrated numerically to determine the velocity and pressure head. Then, an explicit/implicit finite difference method is used to integrate the advection-diffusion-reaction equation (ADRE). A reservoir-pipe-valve-reservoir system illustrates the 2-D behaviour of transient flowdue to a sudden valve opening and results are compared with a one-dimensional (1-D) counterpart. Although the system response using the two models is not dramatically different, the 2-D results do show some discernable increases in realism and insight over the 1-D model. Interestingly, the study also reveals that the Taylor model produces insufficient dispersion in a large-diameter pipe carrying a fully turbulent flow with large Reynolds number.