Inception Point of Air Entrainment and Training Wall Characteristics of Baffles and Sills on Stepped Spillways

An experimental study of new proposed stepped-spillway configurations using sills or baffles on the step treads with sharp or rounded brinks is introduced to investigate the location of and the flow depth at inception point of air entrainment and the training wall height. The silled-shifted rounded spillway is recommended to be used in cavitation damages mitigation because it gives the smallest inception-point length among all spillways for large Froude numbers range. The baffled-edged spillway gives the largest inception-point depth among the spillways for large Froude numbers range and consequently, is not favourable. The baffled-shifted sharp spillway is the most efficient regarding the cost of construction because it gives the smallest training wall height among spillways for large Froude numbers range. The location and depth of inception point of air entrainment and the training wall height were expressed as functions of a so-called roughness Froude number in empirical equations to develop design guidance for the proposed spillway configurations. DOI: 10.1061/(ASCE)HY.1943-7900.0000630. (C) 2012 American Society of Civil Engineers.