Turbulence and air uptake at spillway ramp aerators
The work in this thesis is a physical model of air slot ramp aerators designed to eliminate cavitation in open channel spillway chute flows. The experimental work involves the use of a Laser system to measure the turbulent low structure on a spillway, ramp and jet system, and then to relate the turbulent flow structure to the rate of air entrainment in the aerator. Even though aerator model studies have been carried out for decades, this appears to be the first time that turbulence has been measured in detail, having regard both to the ability of a ramp to generate turbulence and also to the decay of turbulence in the aerator jet downstream of the ramp. An expression is found for air entrainment in the models tested at Glasgow University. It is also valid for a range of previous prototype measurements, and is valid for a range of other previous model studies. The results are also translated into a computer program for designing such structures. The model used was a rectangular cross-section perspex flume, sloping at 45 degrees, incorporating a range of ramps at different angles. A range of flow depths, flow velocities, and boundary roughness values were tested and the measurements were taken by a Laser Doppler Anemometer. The results of this work provide a clearer understanding of the physical processes which occur in aerator ramp. This includes a clear demonstration of the ability of the ramp to generate additional turbulence in the flow, increasing turbulence values by about 30% above normal boundary layer values.