Advection-dispersion transport in water distribution networks with intermittent flow
Por:
Tzatchkov V.G., Aldama A.A., Arreguín F.I., Buchberger S.G., Lee Y.-H.
Publicada:
1 ene 2001
Resumen:
Predictions of known advection-reaction models for one-dimensional transport and decay of constituents in drinking water distribution networks (such as EPANET) tend to be less reliable in pipes with low flow velocity where dispersion may dominate. An Eulerian-Lagrangian advection-dispersion-reaction model (IMTARED) has been developed to accurately predict the concentration evolution in pipes, especially those with laminar flow conditions. This paper extends the proposed advection-dispersion-reaction model to include dispersion in intermittent laminar flow. Intermittent laminar flow conditions are quite common in dead-end zones of water distribution systems. The stop-and-go nature of intermittent flow, however, perpetuates the initialization period during which Taylor's classic theory for dispersion is not valid. It turns out that the effective rate of dispersion is much higher in these conditions (compared to pipes with turbulent and continuous flow) and dispersion is often a significant transport process under low flow conditions. As a consequence, the value of the dispersion coefficient in intermittent laminar flow is much larger compared to that given by Taylor's formulae for dispersion in steady laminar flow. Concentrations predicted by EPANET and IMTARED are compared against field observations. Consideration of dispersion in intermittent laminar flow and the variation of the dispersion coefficient during the initialization period may improve calibration of water quality models applied to distribution systems.