| Macro-turbulent flow downstream a solid roller bucket energy dissipator creates a scour of the downstream bed which physical comprehension of its development and the interaction of various aspects specific to the dissipative-erosive process prove to be necessary to the insurance of the safety of the spillway and the dam as well as the stability of their foundations. The purpose of this thesis is to study the hydrodynamic efforts applied on a mobile bed downstream a solid roller bucket energy dissipator and to associate them to the scour developed downstream. To achieve this goal, a series of scour tests were carried out on a small-scale model, built in the hydraulic laboratory at the department of civil engineering at Laval University, under various hydraulic and geometrical conditions. The progress of the scour process was recorded and the development of the scoured profile as a function of time was marked on the glass wall of the channel. At equilibrium, the bed bathymetry was measured at the center of the channel along the extent of scoured bed. Based on these informations, the bed characteristics at various scour phases as well as the scour evolution rate were deduced. Results of these tests showed that the shape of the bed developed downstream the bucket can be divided into three different zones: a depression zone, a scour zone and a deposition zone. Hydraulic conditions affect the scouring rate and the magnitude of each zone. Bucket's parameters, on the other hand, have an effect not only on the scour characteristics but also modify the shape of the bed particularly in the vicinity of the bucket.; The eroded profiles obtained from scour tests were reproduced on a fixed concrete bed to study the hydrodynamic efforts applied downstream the bucket. The solidified beds (concrete) were equipped with transducers to measure the instantaneous pressure along the longitudinal section in the center of the channel downstream the spillway. The obtained measurements were used to determine the average pressure distributions and those of the pressure fluctuations, and to study the effect of the hydraulic parameters (of the flow) and the geometrical parameters (of the bucket) on these distributions, with respect to the form and the magnitude. (Abstract shortened by UMI.)... |
