Discussion of 'Effect of jet aeration on hydrodynamic forces on plunge pool floors'

摘要

The Discussers congratulate the Authors for their interesting work in the field of hydrodynamic forces on plunge pool floors. The Authors present the effect of jet aeration on mean dynamic pressures at pool floors, based on both analytical computations and small-scale laboratory measurements. Based on air sucked into low-velocity water jets (V = 3.53 m/s), they obtained air concentrations close to the stagnation point of the developed jet at the pool floor of max. 30 percent. The exact pool depth is not provided by the Authors, but has been estimated by the Discussers at roughly 0.70 m, for a jet thickness at impact of roughly 0.70/11.5-0.06 m (h/b = 11.5, being the diffusion length). The corresponding mean dynamic pressure head at jet issuance is thus about 0.65 m. Superposition with the static water head of 0.70 m provides a total relative head of about 1.35 m at the pool floor. The Discussers measured mean air concentrations in plunge pools at the Laboratory of Hydraulic Constructions of the Ecole Polytechnique Federale de Lausanne, Switzerland for high velocity plunging jets (Manso 2006; Manso et al. 2006). The experiments document void fractions at singular points in plunge pools with a flat bottom. Air was entrained naturally in the pool at the jet plunging section. Rough turbulent water jets with very high velocities (up to 30 m/s) were used to replicate prototype pool aeration conditions typically found at large dam spillways. This allows creating air entrainment conditions exempt of significant scale effects in terms of Weber, Reynolds, and Froude numbers.