Journal article
Density Effects at a Concordant Bed Natural River Confluence
Water resources research, Vol.56(4), e2019WR026217
04/2020
DOI: 10.1029/2019WR026217
Abstract
Confluences are locations of complex hydrodynamic conditions within river systems. The effects on hydrodynamics and mixing of temperature‐induced density differences between incoming flows are investigated at a small‐size, concordant bed confluence. To evaluate density effects, results of eddy‐resolving simulations for a densimetric Froude number Fr = 4.9 (weak‐density‐effects cases) and Fr = 1.6 (strong‐density‐effects cases) are compared to results of simulations in which the densities of the incoming flows do not differ (no‐density‐effects cases). Flow patterns predicted for both weak‐ and strong‐density‐effects cases show that secondary flow develops with increasing distance from the confluence apex. The pattern of secondary flow is characterized by denser fluid on one side of the confluence moving near the bed toward the side of the downstream channel corresponding to the less dense fluid and the less dense fluid moving near the free surface in the opposite direction. This pattern of fluid motion is similar to a spatially evolving lock‐exchange cross flow. In the strong‐density‐effects simulations, a cross‐stream cell of secondary flow develops at the density interface between the flows, similar to interfacial billows generated in classical lock‐exchange flows. Density effects increase global mixing with respect to corresponding no‐density‐effects cases regardless of whether the high‐momentum stream contains the higher‐density fluid or the lower‐density fluid. When density effects are weak, the lock‐exchange mechanism either reinforces the pattern of mixing associated with secondary flow induced by inertial forces, particularly helical motion, or opposes this pattern of mixing, depending on which tributary contains the denser fluid. When density effects are strong, flow from the upstream channel with the denser fluid moves under the flow from the upstream channel with the less dense fluid.
Details
- Title: Subtitle
- Density Effects at a Concordant Bed Natural River Confluence
- Creators
- Daniel Horna‐Munoz - Department of Civil and Environmental Engineering and IIHR‐Hydroscience and Engineering The University of Iowa Iowa City IA USA, Environmental Engineering Department, Centro de Investigación y Tecnología del Agua (CITA) Universidad de Ingeniería y Tecnología (UTEC) Lima PeruGeorge Constantinescu - Department of Civil and Environmental Engineering and IIHR‐Hydroscience and Engineering The University of Iowa Iowa City IA USABruce Rhoads - Department of Geography and Geographic Information Science University of Illinois at Urbana‐Champaign Urbana IL USAQuinn Lewis - Department of Geography and Environmental Management University of Waterloo Waterloo ON CanadaAlexander Sukhodolov - Department of Ecohydrology Institute of Freshwater Ecology and Inland Fisheries Berlin Germany
- Resource Type
- Journal article
- Publication Details
- Water resources research, Vol.56(4), e2019WR026217
- DOI
- 10.1029/2019WR026217
- ISSN
- 0043-1397
- eISSN
- 1944-7973
- Grant note
- DOI: 10.13039/100000160, name: Division of Earth Sciences, award: 1359836; DOI: 10.13039/501100001659, name: Deutsche Forschungsgemeinschaft, award: SU 405/10; DOI: 10.13039/100000001, name: National Science Foundation, award: 1359836
- Language
- English
- Date published
- 04/2020
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984066102402771
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