Measurement of physical characteristics of bubbles in gas-liquid plumes: Part I. An improved electroresistivity probe technique

Abstract

This paper presents an experimental study of the structure of turbulent air-water bubble plumes in upwardly injected jets. Part I of the paper describes a microcomputer-aided two-element electro-resistivity probe technique developed for simultaneously determining various important local parameters of the gas phase: gas fraction, bubble frequency, bubble velocity spectrum, and bubble-pierced length spectrum. The measurement of the last two parameters, under the turbulent conditions investigated, necessitated the development of special electronic instrumentation and software to analyze, in real time, the signals produced by the contact of the bubbles with the sensor. The signal analysis, based on pattern recognition logic and the statistics of outliers, eliminated the uncertainties associated with the stochastic nature of the interception of the bubbles with the probe contacts. This permitted the measurement of the velocity of bubbles traveling vertically and undisturbed between the two contacts of the probe. The measuring technique developed was found to be reliable based on the determination of the velocity of single spherical cap bubbles and the consistency between measured and known gas volume flow rates in turbulent gas-liquid plumes.