Bed shear stress under skewed and asymmetric oscillatory flows

Tiago Abreu, Hervé Michallet, Paulo A. Silva, Francisco Sancho, Dominic A. Van Der A, B.G. Ruessink

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalCoastal Engineering
Publication statusPublished - Mar 2013


  • bed shear stress
  • mobile bed
  • oscillatory flow tunnel
  • acceleration skewness
  • velocity skewness
  • sand transport


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