Belueftungseinbauten in Schussrinnen. Wirkungsweise, Formgebung und Berechnung von Schussrinnenbelueftern

As the theoretical knowledge of the air entrainment capacity of spillway chute aerators is scarce, the present study examines the following topics: the physical processes occurring at aerators, the parameters influencing air entrainment at aerators, how can model results be transferred to the prototype, how can results of model and prototype tests be analysed, and is it possible to give general design criteria for air entrainment at aerators. Laboratory and prototype tests for three installations with different geometries were conducted. The formulae derived are compared with prototype results given in the literature. The analysis shows that turbulent shear motions at the air/water interface are the dominant mechanism of air entrainment. The results of the second and third test series show fair agreement between calculated and measured entrainment rates. The extension to prototype results of Foz do Aeria and Amaluza dam are illustrated. For practical design purposes calculations of aerator efficiency have been performed. The results show that steep ramps perform well under all conditions.