Scale effects affecting two-phase flow properties in hydraulic jump with small inflow Froude number

The transition from supercritical to subcritical flow is characterised by a strong dissipative mechanism, a hydraulic jump. Herein a comparative analysis of physical data is presented with a focus on a broad range of two-phase flow parameters. The results show 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 air–water 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, bubble chord time distributions and bubble cluster characteristics. The findings have some implications of civil 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.

► A comparative re-analysis of physical data was conducted for hydraulic jumps with Fr1 = 5.1.
► The Froude similarity was tested for a range of Reynolds numbers 2.5 × 104 < Re < 1.3 × 105.
► A broad range of two-phase flow parameters were tested systematically.
► The bubble count rate data, turbulence properties, bubble chords and clustering properties cannot be up-scaled.
► The findings have some implications in terms of civil engineering designs.