Modeling of Solute Transport in Pore Scale Sediment Beds: A Summary of Hydrodynamic Interactions Induced by Surface Wave, Bed Form, and Near Bed Turbulence

Qin Qian, Vaughan R Voller, Heinz G. Stefan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Solute transport in a pore scale sediment bed of river or lake has a significant effect on chemical mass balances and microbial activities in the water and sediment. The solute transfer between water and a pore scale sediment bed is often described by a "1-D vertical dispersion model" and estimated using molecular diffusion and porosity. However, surface waves, bed forms, and near bed turbulence create periodic pressure waves along the sediment/water interface, which in turn induces flows in the pores of the sediment bed. A coupled 2-D hydrodynamic and solute transport model has been developed to study the solute transport in the pore scale sediment bed, and the solute transport has been incorporated in a 1-D depth dependent "enhanced dispersion coefficient (DE)". Typically, DE diminishes exponentially with depth in the sediment bed. It is a function of the near-bed coherent motion due to the turbulent current, relative dispersivity (longitudinal dispersivity/wave length), wave steepness, sediment hydraulic conductivity, and sediment porosity. Maximum values of DE near the sediment surface can be much larger than molecular diffusion coefficients, e.g., DE ∼ 10cm2/s in a gravel bed with pressure standing waves, DE ∼1 cm2/s in a gravel bed under progressive surface waves, and DE ∼0.1 cm2/s in a gravel bed under near bed turbulent current. The penetration depth due to turbulent is only about 1/5 ∼ 1/10 of that caused by the pressured surface wave. Therefore, the pressured surface wave is a dominant process, and the other processes can be ignored. However, the near-bed turbulent can enhance the transport at least 1 order magnitude than the underflow process along the sediment/water interface.

Original languageEnglish (US)
Title of host publicationWorld Environmental and Water Resources Congress 2014
Subtitle of host publicationWater Without Borders - Proceedings of the 2014 World Environmental and Water Resources Congress
EditorsWayne C. Huber, Wayne C. Huber
PublisherAmerican Society of Civil Engineers (ASCE)
Pages262-271
Number of pages10
ISBN (Electronic)9780784413548
DOIs
StatePublished - Jan 1 2014
EventWorld Environmental and Water Resources Congress 2014: Water Without Borders - Portland, United States
Duration: Jun 1 2014Jun 5 2014

Publication series

NameWorld Environmental and Water Resources Congress 2014: Water Without Borders - Proceedings of the 2014 World Environmental and Water Resources Congress

Other

OtherWorld Environmental and Water Resources Congress 2014: Water Without Borders
CountryUnited States
CityPortland
Period6/1/146/5/14

Keywords

  • computational methods
  • dispersion
  • pore scale sediment
  • solute transport
  • water quality

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