Measurement of the Velocity of Gas Bubbles in Water by a Correlation Method

Abstract

The application of a correlation method for the measurement of gas (vapor) bubble velocity in liquid flow is described. Contrary to previous similar procedures an optical method (laser light) is used for the bubble (or void) detection. First experimental results are reported.

Solids flow measurement by correlation methods

“…Experiments have confirmed that optical sensors generate signals with rather poor correlation coefficients (Section 7). Concluding, the high spatial resolution offered by optical sensors can be exploited only for very small loading by non-reflecting or spherical particles; as a consequence, applications of optical sensors reported in the literature indeed have been restricted to rare bubble flow [4,5] or to plug flow [6] in liquids. An additional disadvantage of optical sensors is the need of transparent windows in the walls, being sensitive to scratching and contamination.…”

“…Various investigations are reported in the literature where the correlation function is computed off-line, such that the transit time T must be read manually from the correlograms. Optical as well as capacitive sensors have been used; among the applications were the velocity measurement of powdered and granular materials in pneumatic conveyors [1,2] and of gas bubbles in fluidized beds [3] or in water [4,5]. Here a simplified, automatic correlating device with on-line read-out is used which had been developed for strip-speed measurement and which has already been successfully applied to twophase gas-liquid flow in capillary tubes [6].…”