Kinematics, Topology and Significance of Dune‐Related Macroturbulence: Some Observations from the Laboratory and Field

Macroturbulence, which may advect through the entire water depth, dominates the flow field associated with alluvial sand dunes and has long been regarded as the principal mechanism for suspending bedload sediment over dunes. The origin of this macroturbulence has been linked to shear layer development in the dune lee, often associated with flow separation, and the form of these coherent flow structures has been noted as 'boils' that erupt onto the water surface. Although past work has quantified the mean and turbulent flow characteristics of flow over dunes using at-a-point measurements, these studies have not been able to trace the evolution of such macroturbulent events over a dune-covered bed. Additionally, the topology of the dune-related macroturbulence has not been explained…