Air Entrainment and Bubble Behavior in Plunge Pools

by Boualem Hadjerioua, Tennessee Valley Authority, Norris, United States,
Emmett M. Laursen, (M.ASCE), Tennessee Valley Authority, Norris, United States,
Margaret S. Petersen, (Hon.M.ASCE), Tennessee Valley Authority, Norris, United States,
Tony A. Rizk, (M.ASCE), Tennessee Valley Authority, Norris, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

This study analyzes air entrainment by falling nappes and bubble behavior in plunge pools, using an experimental-analytical-numerical method. The experimental work was done at the Tennessee Valley Authority (TVA) Engineering Laboratory. An air-water concentration probe (originally proposed by Lamb and Killen, 1950) constructed by TVA was calibrated and used to determine contours of air concentration in the plunge pool of an overflow nappe. High-speed photography was used to determine representative bubble sizes. The air entrainment was computed analytically by integrating the momentum and continuity equations over the air boundary layer of the nappe. A finite difference, fluid flow solver was used to compute a representative water flow field in the plunge pool. Using that water flow field, the trajectory and residence time of bubbles in the plunge pool were computed by solving the two-dimensional Lagrangian equations of motion. The analytical results show good agreement with experimental data collected by the author and other findings documented in the literature.

Subject Headings: Scour | Fluid flow | Water flow | Entrainment | Boundary layers | Equations of motion | Probe instruments

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