Salinity-Induced Density Stratification in Near-Laminar Open-Channel Flows |
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Authors: | Bernhard H Schmid Michael A Hengl Ursula Stephan |
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Affiliation: | 1Senior Lecturer and Professor, Institut für Hydraulik, Gew?sserkunde und Wasserwirtschaft, Technische Universit?t Wien, c/o Vegagasse 16, A-1190 Vienna, Austria. E-mail: schmid@hydro.tuwien.ac.at 2Head, Institut für Wasserbau and hydrometrische Prüfung, Bundesamt für Wasserwirtschaft, Severingasse 7, A-1090 Vienna, Austria. 3Dr. Technical Engineering, Institut für Wasserbau und hydrometrische Prüfung, Bundesamt für Wasserwirtschaft, Severingasse 7, A-1090 Vienna, Austria.
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Abstract: | Salt tracer experiments are a cost-effective tool widely used in studies of flow and transport in free surface flows. Whereas in a large majority of rivers and streams, fully turbulent conditions achieve rapid vertical mixing of injected tracers, this is not necessarily the case with very low Reynolds number flows as encountered e.g., in wetland ponds. There, often laminar to near-laminar transitional flow regimes prevail, and the fact that solutions of elevated salinity are distinctly heavier than water may result in the development of stable density layers, trapping part of the salt tracer and distorting the breakthrough curve recorded at the outlet. In this study, the conditions under which density stratification develops due to salt injection are analyzed, and a criterion is presented which permits an intended salt tracer experiment to be judged at the planning stage already. |
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Keywords: | Density stratification Open channel flow Tracers Salinity |
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