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Title: Bed shear stress under skewed and asymmetric oscillatory flows
Authors: Abreu, T.
Michallet, H.
Silva, P. A.
Sancho, F. E.
Van der A, D. A.
Ruessink, B. G.
Keywords: Bed shear stress;Mobile bed;Oscillatory flow tunnel;Acceleration skewness;Velocity skewness;Sand transport
Issue Date: Jan-2013
Publisher: Elsevier
Abstract: We present a new formulation to predict the bed shear stress under skewed/asymmetric oscillatory flows (with or without a co-linear mean current), extending the work of Nielsen (1992). The nonlinearity of the oscillatory flow is incorporated through the use of two parameters: the index of skewness or nonlinearity, and the waveform parameter. The new formulation is tested against the bed shear stress estimated from the log-fit and momentum-integral methods, using oscillatory data from oscillating water tunnel experiments. The new formulation and the momentum-integral method agree well, but differ from those with the log-fit method, possibly because both methodologies lead to different results for the phase lead between the bed shear stress and the free-stream velocity. The new bed shear stress formulation is incorporated in a quasi-steady bedload formula, and accurately reproduces net transport rates under non-linear, nonbreaking waves with and without an opposing current.
Appears in Collections:DHA/NEC - Comunicações a congressos e artigos de revista

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