Turbulence, Turbulent Mixing and Diffusion in Shallow-wate..-r Estuaries

Abstract

In natural waterways and estuaries, an understanding of turbulent mixing is critical to the knowledge of sediment transport, storm-water runoff during flood events, and release of nutrient-rich wastewater into ecosystems. The predictions of contaminant dispersion in estuaries can rarely be predicted analytically without exhaustive field data for calibration and validation. Why? In natural estuaries, the flow Reynolds number is typically within the range of 10 to 10 and more. The flow is turbulent, and there is an absence of fundamental understanding of the turbulence structure. Any turbulent flow is characterised by an unpredictable behaviour, a broad spectrum of length and time scales, and its strong mixing properties. In his classical experiment, Osborne REYNOLDS (1842-1912) illustrated this key feature with the rapid mixing of dye of a turbulent flow (REYNOLDS 1883). This is seen in Figure 1 showing the original Reynolds experiment and a modified Reynolds experiment. In turbulent flows, the fluid particles move in very in'egular paths, causing an exchange of momentum from one portion of the fluid to another, as shown in Figure 1 where dye is rapidly dispersed in the turbulent flow regime (Re = 2.3 10\ In natural estuaries, strong momentum exchanges occur and the mixing processes are driven by turbulence. Interestingly Osborne REYNOLDS himself was involved in the modelling of estuaries (REYNOLDS 1887). Relatively little systematic research was conducted on the turbulence characteristics in natural estuarine systems, in particular in relatively shallow-water systems. Long-duration

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Cite this paper

@inproceedings{Chanson2010TurbulenceTM, title={Turbulence, Turbulent Mixing and Diffusion in Shallow-wate..-r Estuaries}, author={Huhert Chanson and Mark Trevethan and Hubert Chanson}, year={2010} }