Comparison of concentration measurements with sands

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I. Katopodi, N. Kitou

Wednesday 1 july 2015

12:57 - 13:00h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitches: 8A. Sediment - Erosion

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1. Introduction .In order to contribute towards the study of the sand gradation influence on sediment transport, an experiment in prototype scale took place in the Large Oscillating Water Tunnel of Delft Hydraulics (series K, Chatelus et al, 1998). The sand bed consisted of a 50%-50% mixture of two well-sorted sands (two fractions) with median diameters D50=0.13 mm and D50=0.32 mm. The characteristics of the mixture were D50=0.20 mm and geometric standard deviation _g=1.85. Two hydro- dynamic conditions were used, namely second order Stokes waves and sinusoidal waves superimposed on a mean current. The bed was flat (sheet flow conditions). The parameters measured were net sediment transport rates, vertical profiles of the time-mean suspended concentration, time-dependent sediment concentration both in the suspension layer and the sheet flow layer (as well as time dependent velocities. 2 Comparison of measurements Katopodi et al (1999) presented comparisons of concentration measurements of series K (graded sand) with measurements of series E (well-sorted sand). The sand characteristics in series E were D50=0.21 mm and _g=1.35. In the present work the comparison is extended to the two fractions that compose the graded sand i.e. well sorted sands of D50=0.13 mm and of D50=0.32 mm) that were performed in the same laboratory tunnel. For the total of the 4 sands, for the same hydro-dynamic conditions, the following parameters will be compared: Vertical profiles of the wave-mean sand concentration both in the suspension layer and the sheet flow layer, variation of the D50 of sand samples taken over the depth, time dependent concentrations at various elevations as well as net sediment transport rates.