Author(s): M. Hino; Y. Meng; Y. Fukunishi
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Keywords: No Keywords
Abstract: Oscillatory turbulent shear flows are frequently encountered in the field of hydraulics, such as river flows in tidal estuaries, surging motion of water columns in a penstock and/or a surge tank of a hydroelectric power station, wave motions on a bottom. Three dimensional large-scale turbulent structure of a reciprocating oscillatory turbulent flow in a rectangular duct is investigated experimentally by an array of six hot-wire anemometers. Using conditional sampling technique, t he large scale structures detected in this flow are found to be pairs of counter-rotating fluid motion. These structures grow explosively at the beginning of flow deceleration phase and change their form gradually with phase. The high Reynolds stress production in the decelerating phase (such as that of flood in rising stage indicated by high sediment concentration) is also caused by these structures. Finally, a specially designed flow visualization technique (two colour slit-beam method) confirmed the existence of the large-scale structures of pairs of vortices.
Year: 1989