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The presence of air in open channel flows will increase the bulk of the flow, and is of great importance in the design of spillway and chute sidewalls. Hydraulics in the developed region is investigated in this paper systematically by a series of model and prototype investigations. It is verified that the velocity in the aeration region is the dominant factor. For the flow with an identical velocity but a different flow depth, the air concentration distributions are nearly the same. From the theory based on the formation of drops on the surface by the turbulent liquid jets and the vortex deformation, a formula to calculate the incremental depth is obtained by best correlating the model and prototype investigations. The formula is reasonable with less mean error than those obtained by other methods, which could recommended for the use in engineering designs. [ABSTRACT FROM AUTHOR]

ABSTRACT: The effect of reducing cavitation damage in high-speed flow structure not only relate with entrained air concentration, but also relate with air bubble density has been discovered in recent research. The air bubbles in aerated flow with diameter below then 0.2mm or 0.5mm plays important role in reducing cavitation damage. May be very little air concentration can protect construction free from cavitation erosion. Thereby, measuring bubble size must be emphasized in study of reducing cavitation damage. Measuring bubble size can use probe of needle-type and image usually. By analyses and application experience of velocimeter of air concentration probe of needle-type, suggesting of the median size of bubble d50 adopt measuring data by probe directly, and calculate space distance and density of bubble. Although, the d50 and space distance would be big then real size, and density small then real value. The measuring results have importance value for studying mechanism and establishing a new criterion on entrained air to reduce cavitation damage. [Copyright &y& Elsevier]