Water Resources Research Act Program

Details for Project ID 2009KY129B

Study of turbulent processes driving sedimentation in the rivers of Kentucky

Institute: Kentucky
Year Established: 2009 Start Date: 2009-03-01 End Date: 2010-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $10,901

Principal Investigators: James Fox

Project Summary: Turbulent processes of flow will be studied using both accepted high resolution instruments for study in the lab and field as well as new inexpensive, real-time velocity sensors developed at the University of Louisville that will be calibrated in the laboratory and left in the field for turbulence measurements during high flow events when sediment transport is pronounced. Specific turbulent processes to be investigated include (i) secondary currents responsible for cross-sectional flow in a river and hence erosion of sediment banks and (ii) bursting or ejecting mechanisms at the bed of the river responsible for sediment initiation and erosion and sweeping mechanisms that play a role in deposition. Secondary current is a term describing transverse flow developed in a fully turbulent flow. Secondary currents can be described as multiple circulation cells extending entirely across the channel with adjacent cells rotating in opposite directions. Secondary currents were originally thought to just exist in narrow channels or in curved channels, however, recent work has shown the importance of cellular organization in wide channels and very rough beds as well. This finding suggests a stronger linking of cellular organization with the bursting process than originally hypothesized and thus the interrelationship between these two processes impacting sediment transport will be considered. The bursting phenomenon is commonly observed in turbulent flows over river beds. Bursting includes a series of ejections (low momentum fluid) and sweeps (high momentum fluid) associated with the generation of eddies at the riverbed. Bursting can vary due to different Reynolds numbers, relative roughness, Froude numbers, and wall roughness in general. Previous studies have all been performed in the laboratory and there is a lack of understanding of how these processes and the linkage varies within conditions typical of rivers themselves (dependence of bursting and sediment intiation at moderate Reynolds numbers in the laboratory as compared to high Reynolds numbers in rivers).