Air Entrainment in the Developing Flow Region of Plunging Jets—Part 2: Experimental

When a water jet impinges a pool of water at rest, air bubbles may be entrained and carried away below the pool free surface: this process is called plunging jet entrainment. The study presents new experimental data obtained with a vertical supported jet. Distributions of air concentration and mean air-water velocity, and bubble chord length distributions measured in the developing shear layer are presented. The results indicate that the distributions of void fraction follow closely analytical solution of the diffusion equation. Further, the momentum shear layer and the air bubble diffusion layer do not coincide. Chord length data show a wide range of air bubble sizes and overall the experimental results suggest strong interactions between the entrained air bubbles and the momentum transfer mechanisms.