Author(s): E. Tesaker; S. Roen
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Keywords: No Keywords
Abstract: Tailwater from a power plant is being discharged through a submerged outlet into a lake recipient. Laboratory and theoretical investigations prior to the construction indicated that the diffusion due to submergence would be sufficient to avoid an open water area above the outlet under normal winter conditions. Experience has shown that contrary to this early prediction, an open water area seems to be the usual consequence of the submerged discharge. Since this is usually an unwanted situation, more accurate prediction methods were sought. An investigation has been made during 1985/87 in order to improve the computational methods and the general understanding of the problem. The project includes two parallel parts: 1) A field measurement programme, 2) Modification and adjustment of available computer programs for calculation of the trajectory and dispersion of the jet from the submerged outlet. Important factors influencing and disturbing the original analysis were: 1) natural influx to the lake, 2) the topography of the lake downstream of the outlet, J) varying temperatures in the tailwater from the powerplant, 4) an unplanned upward incline of the jet axis, caused by rock debris on the tunnel floor. In order to cope with the latter factor, it was necessary to modify the available computer program originally made for horizontal jets. After this correction, and calibration of the program with the field temperature data, it was possible to show how a horizontal jet as originally intended, could have led to reduced open water area, or possibly full ice covering of the area.
Year: 1988