a1 Marine Institute, University of Plymouth, Plymouth, UK
a2 NATO Undersea Research Centre, La Spezia, Italy
a3 Dipartimento di Ingegneria delle Costruzioni, dell'Ambiente e del Territorio, Università di Genova, 16145 Genova, Italy
a4 SimCorp A/S, Copenhagen, Denmark
a5 Istituto di Idraulica e Infrastrutture Viarie, Univesità Politecnica delle Marche, Ancona, Italy
The two-way effects of the time-varying suppression of turbulence by gradients in suspended sediment concentration have been investigated using a modified form of the Generalized Ocean Turbulence Model (GOTM). Field measurements of fluid velocities and sediment concentrations collected under high-energy conditions (mobility number ≈ 900) have been simulated both including and neglecting the feedback between sediment and turbulence. The results show that, when present, this feedback increases the wave-coherent component of transport relative to the mean component of transport, which can even change the direction of transport. Comparisons between measured and simulated time series of near-bed sediment concentrations show great coherence (0.95 correlation) and it is argued that the differences in net transport rates may be partially explained by the use of a uniform grain size in the simulations. It is seen that the effects of sediment stratification scale with orbital velocity divided by sediment setting velocity, um/ws, for all grain sizes.
(Received July 10 2007)
(Revised May 02 2008)