Clusters provide bed stability in gravel streams and understanding their formation is important for the development of sediment transport formulas that do not over-predict bedload rates.
Clusters typically consist of three regions, the core, the stoss, and the wake.
Several parameters affect the formation of clusters namely, sediment availability, sediment properties, and sediment flow interaction. While current research has addressed the importance of sediment properties and availability on cluster evolution, the impact of near-bed turbulence on clusters has not been examined. The present study aims to provide a better understanding on the turbulent mechanisms, if any, affecting cluster formation. For this purpose, a generic experiment is designed in a tilting water-recirculating flume to obtain turbulent measurements atop a cluster structure. To prevent possible cluster disintegration during the tests, lead spheres of the same size are used to form stable clusters atop the flume bed.