Sediment Suspension with Rippled Bed

Experiments on the suspension of sediment were performed in flume with and without sediment layer on the bottom. For movable bed runs three‐dimensional sand ripples were found to affect seriously the features of suspended sediment. The horseshoe vortices and the resulting bursts in the lee of the ripples entrain intermittently a large amount of sediment into the outer layer of flow. Details of the suspension process were studied using a sand ripple model made of plaster. The result revealed that the vertical component of turbulent eddies is responsible for the suspension of sediment, and the statistical distribution of the component was found to be the Gaussian law. The statistical distribution of the concentration fluctuation was observed to be highly skewed, and the reason was determined to be the fact that the concentration increases with the power of eight against the vertical fluid velocity. The period of the intermittent ejection of sediment agreed reasonably with those reported for natural geophysical flows. Thus, the suspension of sediment in flows with rippled beds was proven to be significantly correlated with bursting phenomenon behind sand ripples.