Modeling Solute Transport Using Quick Scheme

Abstract

Details are given of the refinement and application of a two‐dimensional depth integrated numerical model to predict the depth mean velocity field and the spatial concentration distribution in hydraulic basins, such as chlorine contact tanks. The model includes a refined and computationally manageable third‐order spatial finite‐difference representation of the terms describing the advective transport of a solute, with the corresponding difference scheme being particularly suited to modeling high solute gradients. The scheme is shown to yield high accuracy in comparison with the more conventional second‐order central‐difference representation, with the associated spurious wavetype distribution solute concentrations associated with high‐solute gradients being considerably reduced. The model has been applied to a laboratory hydraulic model study of plug flow through a site‐specific chlorine contact tank, with the numerical model results for various tank configurations being compared with corresponding laboratory model results. In most cases the numerical model predictions of the flow through curves for a conservative tracer were in close agreement with the corresponding laboratory model results, particularly in comparison with the predictions obtained using a central difference representation.