COMPARATIVE ANALYSIS OF SUSPENDED SAND CONCENTRATION RECORDED WITH DIFFERENT TECHNIQUES IN A RIPPLED BED REGIME

  • Alireza Ahmari Coastal Research Centre (FZK)
  • Hocine Oumeraci
  • Joachim Gruene
Keywords: Non-breaking waves, suspended sediment concentration, sediment transport, Acoustic Backscatter Sensor, intra wave processes, vortex ripple

Abstract

Sediment entrainment processes due to the oscillatory flow above rippled and plane sea beds are fundamentally different. Whereas above plane beds the sheet flow or bed load regime dominates and the momentum transfer is primarily caused by turbulent diffusion, above a sea bed covered with long crested vortex ripples the well organised coherent vortex mechanisms induce sediment-laden lee vortices at the ripple crest, which will be detached from the bed ejected into the water column and finally shed when the flow reverses. To investigate the sediment entrainment processes above vortex ripples, a study was carried out in the Large Wave Flume (GWK) aiming firstly to find out the most appropriate measuring technique to determine the suspended sediment concentration both temporarily and spatially. and secondly to analyse the intra-wave sediment entrainment processes around a steep ripple.

References

Ahmari A., Gruene, J., Oumeraci, H. 2008, Large scale laboratory measurement of suspended sediment concentration induced by non-breaking waves with acoustic backscatter technique, Proc. on App. of Phy. Mod., Coastlab'08, Bari, Italy, 93-105.

Nielsen P.1992, Coastal Bottom Boundary Layers and Sediment Transport, Advanced series on Coastal Engineering- Volume 4, World Scientific.

Thorne, P. D., Williams, J.J. and Davies, A.G. 2002, Suspended sediment under waves measured in a large-scale flume facility. Journal of Physical Research. Vol. 107, No. C8, 4.1-4.16.

Thorne, P. D. and Hanes D. M. 2002. A review of the application of acoustics to small scale sediment processes. Continental Shelf Research, 22(4), 603-632. http://dx.doi.org/10.1016/S0278-4343(01)00101-7

Thorne, P. D., Davies A. G., Williams J. J. 2003. Measurements of near bed intra-wave sediment entrainment above vortex ripples. Geophys. Res. Lett., Vol. 30, No. 20, 2028, OCE, 2-1 - 2-4.

Thorne, P. D., Davies, A. G. and Bell, Paul S. 2009, Observations and analysis of sediment diffusivity profiles over sandy rippled beds under waves, J. Geophys. Res. Vol. 114 C02023. 1-16. http://dx.doi.org/10.1007/s10712-008-9039-x

Davies, Alan G., Thorne, P. D. 2008, Advance in the Study of Moving Sediment and Evolving Seabed, Surv Geophys 29:DOI 10.1007/s10712-008-9039-x. 1-36. http://dx.doi.org/10.1007/s10712-008-9039-x

Published
2011-01-30
How to Cite
Ahmari, A., Oumeraci, H., & Gruene, J. (2011). COMPARATIVE ANALYSIS OF SUSPENDED SAND CONCENTRATION RECORDED WITH DIFFERENT TECHNIQUES IN A RIPPLED BED REGIME. Coastal Engineering Proceedings, 1(32), sediment.9. https://doi.org/10.9753/icce.v32.sediment.9

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