Preliminary communication

Approach to modelling natural convection in reservoirs as exemplifi ed by the Butoniga reservoir

Luka Zaharija ; Faculty of Civil Engineering, University of Rijeka, Rijeka, Croatia
Davor Stipanić ; Hidromodeling, d.o.o., Rijeka, Croatia
Vanja Rački ; Hrvatske vode, Rijeka, Croatia
Maja Oštrić ; Hrvatske vode, Rijeka, Croatia
Vanja Travaš ; Faculty of Civil Engineering, University of Rijeka, Rijeka, Croatia

Abstract

In the context of reservoir management, natural convection, i.e. volumetric flow occurring as a consequence of the temperature gradient is a particularly important physical process that can significantly influence the decision-making and reservoir management processes. This will be illustrated by the paper on the example of the Butoniga reservoir, in which natural convection plays a very significant role. In the summer period, a thermocline is formed in the Butoniga reservoir and thus anoxic conditions are induced in the lower near-bottom layer that, in the presence of mud at the reservoir bottom and through biological and chemical processes, significantly deteriorate water quality in this area. As long as there is a balanced thermal stratification, the mixing of this anoxic layer with the remaining water is prevented. However, due to a progressive decrease in the mean air temperature value in the early autumn period, the top water layer cools down and a significant vertical circulation begins, which may cause the mixing of the anoxic layer and endanger the quality of the remaining water in the reservoir through natural convection. For this reason, it is necessary to forestall the moment when vertical circulation is activated and empty the near-bottom layer of the reservoir. The decision-making regarding the moment when the reservoir should be emptied is an elaborate process that is based on the previously performed field measurements and very complex computer simulations. After the most appropriate time of the reservoir emptying is established, which requires a comprehensive parameter analysis, the attention is focused on the determination of the most efficient emptying dynamics, which is the topic of this paper.

Keywords

Butoniga reservoir; early autumn discharge; numerical model; OpenFOAM

Hrčak ID:

214854

URI

https://hrcak.srce.hr/214854

Publication date:

27.12.2018.

Article data in other languages: croatian

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