Author(s): Y. Chachereau; H. Chanson
Linked Author(s): Hubert Chanson
Keywords: Hydraulic jumps; Air entrainment; Dynamic similarity; Physical modelling; Scale effects
Abstract: The transition from supercritical to subcritical flow is characterised by a strong dissipative mechanism, a hydraulic jump. In the present study, the air-water properties were investigated experimentally in hydraulic jumps with relatively small Froude numbers (2.4 < Fr1 < 5.1) and relatively large Reynolds numbers. A comparative analysis demonstrated that, for hydraulic jumps with Fr1 = 5.1, the void fraction data obtained with Re < 4×104 could not be scaled up to Re = 1×105. Most airwater flow properties measured with Reynolds numbers up to 1.25×105 could not be extrapolated to large-size prototype structures without significant scale effects in terms of bubble count rate, turbulence and bubble chord time distributions. The findings have some major implications of civil, environmental and sanitary engineering designs, because most hydraulic structures, storm water systems and water treatment facilities operate with Reynolds numbers larger than 106 to over 108.
Year: 2011