The Relation Between Flow Turbulence and Mixing Along A Stream Confluence Shear Layer

Zhou, Yayu

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https://hdl.handle.net/2142/90256 Copy

Description

Title

The Relation Between Flow Turbulence and Mixing Along A Stream Confluence Shear Layer

Author(s)

Zhou, Yayu

Contributor(s)

Lewis, Quinn W.

Issue Date

2016

Keyword(s)

• confluence
• shear layer
• mixing interface
• turbulence
• velocities

Abstract

River confluences are characterized by different variables such as velocity and turbidity. When two flows collide, velocity is inherently more complex than in a single channel. Two different flows may carry water with significantly different loads (e.g. sediment, pollution, temperature), which means that confluences are important foci of mixing within river networks. How the 3-D velocities change at the mixing interface? Are there any obvious pattern for the velocities? What is the generated kinetic energy and how does it impact the flow transportation ability? To answer these questions, we collected data calculated from point-location probes, which can measure 3D velocity and turbidity. These probes are deployed from custom-built equipment designed to move them to numerous locations within a slice or cross section of a river. Confluence are critical zones of mixing within stream networks. The confluent streams often carry significantly different loads or contain water at dissimilar temperatures. The normally slow mixing processes in streams are considerably enhanced at confluences, where non-zero junction angles and intense velocity shear promote strong cross-stream flow and large amounts of velocity turbulence respectively. This study uses 3D velocity time series data obtained from acoustic probes to assess mixing processes along a confluence shear layer. These data reveal that the amount of mixing accomplished by shear-generated turbulent structures differs with depth and varies between different flows at the same confluence.

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/90256

Copyright and License Information

Copyright 2016 Yaya Zhou

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