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Oscillations in a Channel with Rectangular Widenings at the Side Walls

Author(s): T. Meile; J. L. Boillat; J. Dubois; A. J. Schleiss

Linked Author(s): Anton J. Schleiss

Keywords: Water surface oscillations; Open channel flow; Groin fields; Embayment; Cavity; Harbours

Abstract: In several studies on cavities, river embayments, groin fields or harbours transverse or longitudinal water body movements have been observed. Most of these studies are dealing either with a single cavity (embayment), spur dikes at only one channel side or a limited range of cavity geometries. In the presented study, a large range of cavity geometries (rectangular widenings) with different aspect and expansion ratios have been investigated in a 40 m long channel. Tests with axi-symmetric cavities have been performed for different subcritical free surface flow conditions. For particular geometrical configurations and hydraulic conditions, significant and periodic transverse movements of the water bodies contained in the widened reaches have been observed. The water body movements are leading to periodic oscillations of the water surface. The frequency of these oscillations is almost in good agreement with the natural frequency of the water body in a rectangular basin assuming the first order mode of sloshing perpendicular to the mainstream. At particular Strouhal numbers, resonance phenomenon related to standing waves leads to peaking values of the water surface oscillations. In some cases, the observed mean wave heights can reach more than 20% of the mean flow depth.

DOI:

Year: 2007

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