Velocity and concentration measurements in multiphase flows by NMR

Abstract A nuclear magnetic resonance technique for the quantitative and noninvasive determination of flow-induced structure of a multiphase system is introduced and illustrated. It is a three-dimensional Fourier transform method in which a slice perpendicular to the flow is selected, frequency encoding is performed in the flow direction, and phase encoding is performed in the other two mutually orthogonal directions. Spatially resolved concentration and velocity profiles are extracted from this complete set of data. In particular, the nonuniform velocity and concentration profiles which result from a suspension of negatively buoyant particles flowing in a straight circular pipe are obtained. The average velocity range studied was between 1.6 and 31 cm/s and the average solid phase concentration was 10% by volume. The method is applicable to a wider range of these parameters, including much higher solid concentrations. Thus, we have been able to characterize a system which is difficult or impossible to study by other methods.