Computational and Experimental Modeling of Ejection Effect in Hydroeletric Plants

Due to the importance of environmental preservation, it is difficult to construct new hydroelectric plants. Therefore, it is required that the design technology considers the best use of natural resources, taking full advantage of the potential in each hydroelectric plant. This study focus on the fact that if properly used the excess flow can increase the power plant head. It is suggested that part of the flow to be released through the spillway can be discharged next to the draft tube of the power house (through the use of bottom outlets) leading to an increase in the power head by ejection effect. The interaction between flows from the power house and the bottom outlets is complex to analyze by analytical methods, making it difficult to determine the additional head due to ejection effect. It is possible to determine the ejection effect with a physical model but this study proposes the use of a computational model, the software OpenFOAM. The computational simulations showed good agreement to a 1:70 scale physical model and the results showed that the simplified method proposed by Sliiskii (1953) leads to underestimate the additional head for the studied case.