Turbulence Intensity and Integral Turbulent Scales on a Stepped Spillway in Skimming Flows

Stepped spillways are a form of flood release facility. Flows down stepped spillways are characterised by a high rate of energy dissipation. They are however characterised by complex turbulent processes. Physical experiments were conducted on a large-size stepped spillway model at the University of Queensland operating with large discharges: i.e., for a skimming flow regime. Extensive measurements were conducted to provide a better understanding of the interactions between mainstream turbulence, step cavity recirculation and free-surface aeration. The present study focused on the turbulence properties including turbulence intensity and integral turbulent scales. Downstream of the inception point of free-surface aeration, the distributions of turbulence intensities highlighted an alternation of vertical profiles every two step edges linked with some form of vortex shedding. The distributions of integral turbulent time and length scales were measured at several step edges for several discharges. The results highlighted the strong turbulence levels and turbulent dissipation in the intermediate flow region defined as 0.3 < C < 0.7. This region within the bulk of the flow played an important role in terms of energy dissipation. The results demonstrated some characteristic maxima of integral turbulent scales and self-similar relationships between some characteristic dimensionless integral turbulent scales and the Reynolds number