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Horizontal momentum jets in rotating basins

Published online by Cambridge University Press:  29 March 2006

Stuart B. Savage
Affiliation:
Department of Civil Engineering and Applied Mechanics, McGill University, Montreal, Canada
Rodney J. Sobey
Affiliation:
Sonderforschungsbereich 80, Karlsruhe University, Karlsruhe, Germany Present address: Department of Engineering, James Cook University, Townsville 4811, Australia.

Abstract

In order to prevent stagnation and improve water quality, the intakes of many water-supply reservoirs have the form of momentum jets directed approximately radially into the storage. An analysis which idealizes this flow as consisting of a turbulent jet issuing horizontally from a circular orifice into a large rotating basin of deep water shows that the jet path is a spiral whose length scale L depends upon the rate of rotation and the kinematic momentum of the jet. Good agreement is found with flow-visualization experiments when the basin depth h is ‘large’ (h/L [gsim ] 0·21). For small depths (h/L [lsim ] 0·024) the flow tends to be twodimensional and the jet path is found to be straight. Full-scale reservoirs are usually shallow enough that the effect of the earth's rotation on the jet path is likely to be small. However these reservoirs are not inordinately shallow and tests with distorted hydraulic models are likely to show significant effects of rotation and can be misleading to the unsuspecting.

Type
Research Article
Copyright
© 1975 Cambridge University Press

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