Hierarchical modeling of the dilute transport of suspended sediment in open channels |
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Authors: | Fabián A Bombardelli Sanjeev K Jha |
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Institution: | (1) Department of Civil and Environmental Engineering, University of California, Davis, 2001 Eng. III, One Shields Ave., Davis, CA 95616, USA |
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Abstract: | We propose, discuss and validate a theoretical and numerical framework for sediment-laden, open-channel flows which is based
on the two-fluid-model (TFM) equations of motion. The framework models involve mass and momentum equations for both phases
(sediment and water) including the interactive forces of drag, lift, virtual mass and turbulent dispersion. The developed
framework is composed by the complete two-fluid model (CTFM), a partial two-fluid model (PTFM), and a standard sediment-transport
model (SSTM). Within the umbrella of the Reynolds-Averaged Navier-Stokes (RANS) equations, we apply K–ε type closures (standard and extended) to account for the turbulence in the carrier phase (water). We present the results
of numerical computations undertaken by integrating the differential equations over control volumes. We address several issues
of the theoretical models, especially those related to coupling between the two phases, interaction forces, turbulence closure
and turbulent diffusivities. We compare simulation results with various recent experimental datasets for mean flow variables
of the carrier as well as, for the first time, mean flow of the disperse phase and turbulence statistics. We show that most
models analyzed in this paper predict the velocity of the carrier phase and that of the disperse phase within 10% of error.
We also show that the PTFM provides better predictions of the distribution of sediment in the wall-normal direction as opposed
to the standard Rousean profile, and that the CTFM is by no means superior to the PTFM for dilute mixtures. We additionally
report and discuss the values of the Schmidt number found to improve the agreement between predictions of the distribution
of suspended sediment and the experimental data. |
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Keywords: | K– ε model Partial two-fluid model Reynolds-Averaged Navier-Stokes (RANS) equations Sediment transport Suspended sediments Turbulence modeling Two-fluid model (TFM) Two-phase flows |
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