Hostname: page-component-586b7cd67f-t7czq Total loading time: 0 Render date: 2024-11-23T01:28:18.257Z Has data issue: false hasContentIssue false
  • English
  • Français

Turbulent spots in oscillatory boundary layers

Published online by Cambridge University Press:  19 September 2011

Marco Mazzuoli ,
Giovanna Vittori  and
Paolo Blondeaux
Marco Mazzuoli
Affiliation:
Department of Civil, Environmental and Architectural Engineering, University of Genoa, 16145, Genoa, Italy
Giovanna Vittori*
Affiliation:
Department of Civil, Environmental and Architectural Engineering, University of Genoa, 16145, Genoa, Italy
Paolo Blondeaux
Affiliation:
Department of Civil, Environmental and Architectural Engineering, University of Genoa, 16145, Genoa, Italy
*
†Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Detailed knowledge of the dynamics of vortex structures in an oscillatory boundary layer is essential for the correct modelling of transport processes in many engineering problems and, in particular, of the pick-up and transport of sediments at the bottom of sea waves. In the present contribution, the formation of turbulent spots in an oscillatory boundary layer is investigated by means of direct numerical simulations. Two of the laboratory experiments of Carstensen, Sumer and Fredsøe are reproduced and, after a comparison of the numerical results with laboratory measurements, a detailed and quantitative characterization of the turbulent spots is also given on the basis of further simulations. The speeds of the head () and tail () of the spots are found to scale with the instantaneous free stream velocity and to be similar to those observed in steady boundary layers. The ratios and seem to increase with the Reynolds number () while the streamwise expansion rate of the spots appears to be independent of .

JFM classification

Instability: Transition to turbulence
Type
Papers
Information
Journal of Fluid Mechanics , Volume 685 , 25 October 2011 , pp. 365 - 376
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Blondeaux, P. & Vittori, G. 1994 Wall imperfections as a triggering mechanism for Stokes-layer transition. J. Fluid Mech. 264, 107–135.Google Scholar
2. Carstensen, S., Sumer, B. M. & Fredsøe, J. 2010 Coherent structures in wave boundary layers. Part 1. Oscillatory motion. J. Fluid Mech. 646, 169–206.CrossRefGoogle Scholar
3. Costamagna, P., Vittori, G. & Blondeaux, P. 2003 Coherent structures in oscillatory boundary layers. J. Fluid Mech. 474, 1–33.Google Scholar
4. Davies, A. G., Ribberinkb, J. S., Temperville, A. & Zyserman, J. A. 1997 Comparisons between sediment transport models and observations made in wave and current flows above plane beds. Coast. Engng 31, 163–198.CrossRefGoogle Scholar
5. Emmons, H. 1951 Laminar-turbulent transition in boundary layer. J. Aeronaut. Sci. 18 (7), 490–498.Google Scholar
6. Fishler, L. S. & Brodkey, R. S. 1991 Transition, turbulence and oscillating flow in a pipe. Exp. Fluids 11, 388–398.Google Scholar
7. Jensen, B. L., Sumer, B. M. & Fredsoe, J. 1989 Turbulent oscillatory boundary layers at high Reynolds numbers. J. Fluid Mech. 206, 265–297.CrossRefGoogle Scholar
8. Jeong, J. & Hussain, F. 1995 On the identification of a vortex. J. Fluid Mech. 285, 67–94.Google Scholar
9. Orlandi, P. 1989 A numerical method for direct simulation of turbulence in complex geometries. Annual Research Brief, 215. Center for Turbulence Research, Standford University.Google Scholar
10. Ribberink, J. S. & Al-Salem, A. A. 1995 Sheet flow and suspension of sand in oscillatory boundary layers. Coast. Engng 25, 205–225.Google Scholar
11. Sarpkaya, T. 1993 Coherent structures in oscillatory boundary layers. J. Fluid Mech. 253, 105–140.CrossRefGoogle Scholar
12. Schubauer, G. B. & Klebanoff, P. S. 1955 Contributions on the mechanics of boundary-layer transition. NACA TN-3489.Google Scholar
13. Singer, B. A. 1996 Characteristics of a young turbulent spot. Phys. Fluids 8 (2), 509–521.CrossRefGoogle Scholar
14. Vittori, G. 2003 Sediment suspension due to waves. J. Geophys. Res. 108 (6), 3173.Google Scholar
15. Vittori, G. & Verzicco, R. 1998 Direct simulation of transition in an oscillatory boundary layer. J. Fluid Mech. 371, 207–232.CrossRefGoogle Scholar