Study of coherent turbulent flow over the ripples using Particle Image Velocimetry

The structure of turbulent flow over ripples is important to understand initiation of sediment entrainment and transport. The focus of this study is the measurement and analysis of the dominant bursting events and the flow structure over the ripples in the bed of a channel. One type of ripple with sinusoidal form was tested in this study. The velocities of flow over the ripples were measured in three dimensions using Particle Image Velocimetry (PIV). These velocities were measured at different points within the flow depth from the bed and at different longitudinal positions along the flume. It was found that upstream of the ripple crest, transition probability of stable organization (P44) were dominant when compared to other 15 transition probabilities. This can be interpreted as an expectation that entrainment should occur at this location. However, downstream of the ripple crest, transition probability of zone 2 to zone 3 (P23) and transition probability of zone 3 to 4 (P34) were more dominant than others. Therefore would be expected sedimentation to occur at this location