Author(s): X. Chassagneux F. -; D. Hurther

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Abstract: This study presents collocated and synchronized wave channel measurements of wave height, 2D velocity profile and video images, taken at three cross-shore positions across the wave breaking region of an irregular wave field. The experiments are conducted over a mobile PVC sediment bed reproducing the cross shore variation of sediment transport regimes typically seen along sandy beach profiles. We discuss the relative importance of orbital shear stress, turbulent normal and shear stress dependent on wave velocity skewness, acceleration skewness, wave breaking state and wave group effects. In particular, distinction between turbulence induced by wave breaking (bore turbulence) and bed friction effects are clearly observed. In the near bed region, two peaks per wave ofr ms u ′ correlate well with the negative peaks of Reynolds shear stress. The highest peaks ofr ms w′ are associated with positive peaks of Reynolds shear stress. Within the irregular wave sequence, a wave with a large positive acceleration skewness and a low velocity skewness, has a positively skewed orbital bed shear stress. However, due to important differences in bed shear stress estimations using three different methods, it is still uncertain to attribute these results to wave acceleration skewness. Wave group effects seem to play an important role in sediment transport across the wave breaking region.

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Year: 2009