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Hyporheic Exchange Driven by Three‐Dimensional Sandy Bed Forms: Sensitivity to and Prediction from Bed Form Geometry

Chen, Xiaobing ; Cardenas, M. Bayani ; Chen, Li

Water resources research, 2018-06, Vol.54 (6), p.4131-4149 [Periódico revisado por pares]

Washington: John Wiley & Sons, Inc

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  • Título:
    Hyporheic Exchange Driven by Three‐Dimensional Sandy Bed Forms: Sensitivity to and Prediction from Bed Form Geometry
  • Autor: Chen, Xiaobing ; Cardenas, M. Bayani ; Chen, Li
  • Assuntos: bed form ; Bed forms ; Biogeochemistry ; Computational fluid dynamics ; Computer applications ; Curvature ; dune ; Dynamics ; Exchanging ; Fluid dynamics ; Fluid flow ; Fluvial sediments ; Hydrodynamics ; hyporheic exchange ; Hyporheic zone ; Mathematical models ; Parameter sensitivity ; Parameters ; Physiographic features ; Predictions ; Pressure ; Residence time ; Reynolds number ; river ; River beds ; River channels ; Rivers ; Sediment ; Sedimentary structures ; Sediments ; Stress concentration ; Surface flow ; three‐dimensional ; Water flow ; Water quality ; Watersheds ; Wavelength ; Wavelengths
  • É parte de: Water resources research, 2018-06, Vol.54 (6), p.4131-4149
  • Descrição: Bed form‐driven hyporheic exchange is vital to biogeochemical processes occurring within aquatic sediment. The integrated effects of hyporheic processes in a bed form ultimately impact watershed‐scale water quality. However, much of what is understood regarding bed hyporheic exchange is based on idealized two‐dimensional bed forms despite the prevalence of potentially complex three‐dimensional (3‐D) bed forms in sandy riverbeds. We thus examined the impact of bed form three‐dimensionality on hyporheic exchange. Bed form three‐dimensionality was represented by two groups of geometric parameters: (1) crest planform curvature and (2) transverse and longitudinal wavelength and amplitude. A wide variety of synthetic bed forms was generated based on the geometric parameters. Then, surface flow over and hyporheic flow through each bed form was calculated using a 3‐D multiphysics computational fluid dynamics model implemented across a range of Reynolds Number. We found that hyporheic exchange is sensitive to both types of parameters that determine the bed form three‐dimensionality. Hyporheic exchange is dominated however by the three‐dimensionality caused by out‐of‐phase superimposed sinusoidal surfaces. The results of the complex flow models were synthesized into simple equations for predicting hyporheic flux and bulk residence time based on bed form longitudinal and transverse wavelengths, bed form height, and Reynolds Number. Plain Language Summary Many rivers have beds comprised of sediment. The sediment usually form topographic features such as bed forms like dunes and ripples. Water flow in the river above the bed form‐covered bed produces a complex distribution of pressure. The variability of pressure causes water to flow from the river into the sediment in areas where pressure is high and back into the river where pressure is low. This process called hyporheic exchange is responsible for many biochemical reactions occurring within the sediment. Hyporheic exchange has been shown to impact over‐all water quality across a watershed with a network of river channels because of this. In many situations, the bed forms that develop display complex three‐dimensional patterns, but the state‐of‐the‐science of hyporheic exchange dynamics is largely based on investigations of simple two‐dimensional shapes. We used sophisticated computational models of flow in the river and in the hyporheic zone of the sediment bed to analyze 3‐D hyporheic flow for close to 1,000 combinations of 3‐D bed form shapes and hydraulic conditions. The hundreds of model outputs were reduced to simple equations that can be used to estimate how much water flows through the hyporheic zone and how much time this water spends within it. Key Points Effects of bed form three‐dimensionality on hyporheic exchange are examined by modeling flow in hundreds of complex synthetic bed forms Hyporheic exchange across complex bed forms is dominated by the three‐dimensionality caused by the bed form wavelengths and amplitudes A set of parsimonious models for predicting bed form‐induced hyporheic flow are provided
  • Editor: Washington: John Wiley & Sons, Inc
  • Idioma: Inglês
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