Conditions when anisotropy is negligible for solute transfer in sediment beds of lakes or streams |
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| Authors: | Qin Qian Vaughan R Voller Heinz G Stefan |
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| Institution: | 1. Department of Civil Engineering, Lamar University, Beaumont, TX 77710, USA;2. Department of Civil Engineering, St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414, USA |
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| Abstract: | To reduce the complexity and save computation time, an isotropic and a scalar dispersion model are explored and compared to the anisotropic advection/dispersion model to study the interstitial flow in a stream and lake sediment induced by a periodic pressure wave. In these systems, the solute transport is controlled by the ratio (R = a/(LS)) of the pressure wave steepness (a/L) to the stream slope (S), and the dispersivity ratio (λ = αL/L) that measures the longitudinal dispersivity (αL) relative to the pressure wave length (L). Through a series of numerical experiments, the conclusion is reached that a scalar dispersion model can be applied with satisfactory results for advection-dominated transport, i.e. when R ? 0.1 and λ ? 0.01, or λ ? 0.0001, i.e. Peclet number (Pe) ? 10000; an isotropic dispersion model can be applied when R ? 10 or λ ? 0.001, and the full anisotropic advection/dispersion model has to be applied when R > 10 and λ > 0.001. |
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| Keywords: | Model Solute transfer Sediment Interstitial flow Advection Dispersivity |
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