Air–Water Properties in Rectangular Free-Falling Jets

This study analyzes the air–water flow properties in overflow nappe jets. Data were measured several cross-sections of rectangular free-falling jets downstream a sharp-crested weir, with maximum fall distance 2.0 m. The obtained using conductivity phase-detection probe. Furthermore, back-flushing Pitot-Prandtl probe was used order to obtain velocity profiles. Five specific flows rates analyzed, from 0.024 0.096 m3/s/m. measurements allowed us characterize increment air entrainment during fall, affecting characteristic distributions, reducing non-aerated water inner core, and increasing lateral spread, thereby leading changes jet thickness. results showed slight differences between upper lower trajectories. experimental data thickness related local void fraction 50% seemed be similar due only gravitational effects until break-up length reached. amount energy tended remain constant falling over 15 times greater than total head weir crest, at which entrained affected entire cross-section, core disappear. new experiments allow improve current knowledge turbulent