Two-phase flows by pulsed field gradient spin-echo NMR

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Abstract
Pulsed field gradient nuclear magnetic resonance was performed on air-water mixtures flowing through a circular pipe. Analysis of the spin echo signals established the validity of the technique to measure the mean velocity and the velocity probability distribution in laminar and turbulent flows of liquid water (one phase) in a long circular pipe. The purpose of this study was to extend the method to the case of two-phase air-water flows. A full procedure is proposed and demonstrated for deriving different basic characteristics of these flows: void fraction, mean liquid velocity, liquid volumetric flux and mean velocity probability distribution. The experimental results, reported for various void fractions (0-0.5) and liquid volumetric fluxes (up to 25 cm s-1), extensively illustrate the capabilities of this method.