Hydrodynamic behavior of asymmetric oscillatory boundary layers at low reynolds numbers

Ahmad Sana, Hitoshi Tanaka, Hiroto Yamaji, Ikuo Kawamura

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


An experimental and numerical study has been carried out to study the wave boundary layers under asymmetric waves. The experiments were conducted in an oscillating tunnel using a simple mechanical system to generate an asymmetric oscillatory motion similar to cnoidal waves. The velocities were measured by laser Doppler velocimetry and the bottom shear stress was calculated from the cross-stream velocity profile. A low Reynolds number k-ε model was used to predict the hydrodynamic properties of the cnoidal wave boundary layers. After validating the model with the experimental data, a series of numerical experiments were carried out to study the transitional behavior of these boundary layers by virtue of friction factor and phase difference between mean free-stream velocity and bottom shear stress. Finally a stability diagram was drawn to demarcate the laminar, transition, and fully turbulent regimes using the numerical results. The present study would be useful for the hydraulic and coastal engineers interested in calculating bottom shear stress in order to compute the sediment transport in coastal environments.

Original languageEnglish
Pages (from-to)1086-1096
Number of pages11
JournalJournal of Hydraulic Engineering
Issue number10
Publication statusPublished - 2006 Oct


  • Friction
  • Hydrodynamics
  • Numeric models
  • Oscillatory flow
  • Reynolds number
  • Shear stress
  • Turbulent flow


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