Author(s): Georg Moller; Martin Detert; Robert M. Boes
Linked Author(s): Martin Detert
Keywords: No Keywords
Abstract: A major design criterion of intakes has usually been to avoid air entrainment by vortices. This paper gives a review of intake vortices research regarding the quantification of entrained air. Only four publications dealing with air entrainment were found in a literature review. However, no useful information is provided to quantify the air entrainment. A correlation with essential flow parameters is missing. In a large number of publications the term “air entraining vortices” is used, but no information is given regarding air entrainment. The present paper further describes the consequences of air being entrained into a pressure system. It is discussed how the knowledge of the air entrainment rate could be used for a new design concept improving the safety, durability and efficiency of hydropower waterways. Two general measures are emphasized: (1) the common way to avoid air entrainment completely, and (2) a new approach to allow air entrainment. A largescale model has been built at VAW of ETH Zurich and tests to quantify the air entrainment rate due to intake vortices are currently conducted. Moreover, the physical processes of air transport mechanism in the air core and bubble separation from the air core to a pressure pipe system have been analyzed. The velocity field of an intake vortex is measured by 2D Particle Image Velocimetry (PIV). The results will allow correlating the air entrainment rate to the leading hydraulic parameters, e. g. the circulation of a vortex.
Year: 2012