EXPERIMENTAL ANALYSIS OF RELATION BETWEEN COHERENT TURBULENT STRUCTURES AND BED-FORMS FORMATION

The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measures of flow velocity components have been carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) has been verified through the conditioned quadrant analysis. The quantitative information about the spatial and temporal evolution of turbulent events has been obtained through the space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence the bed-forms formation, the spatial scale of turbulent events evolution has been compared with the wavelength of bed-forms (alternate bars) observed on the bed. The analysis has essentially highlighted that such spatial scale compares well with the bars wavelength.