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

摘要

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 Fr_1=5.1, the void fraction data obtained with Re<4×10~4 could not be scaled up to Re=1×10~5. Most air-water flow properties measured with Reynolds numbers up to 1.25×10~5 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 10~6 to over 10~8.