NMR flow imaging of fluids and solid suspensions in Poiseuille flow

Abstract

The application of nuclear magnetic resonance (NMR) flow imaging to the study of Poiseuille flows of single‐phase fluids and solid/liquid suspensions is demonstrated and investigated. Two fluids were studied: a mixture of a low‐molecular‐weight polyether oil and water which is Newtonian and an aqueous solution of a high‐molecular‐weight polymer which is non‐Newtonian. The velocity profiles of these fluids in Poiseuille flow measured by NMR are in excellent agreement with those predicted from viscometric data using a power law model. The suspensions investigated consisted of density‐matched compositions of solid poly(methyl methacrylate) beads of various concentrations up to 52% in a Newtonian, polyether‐based liquid. At particle loadings above 40% these suspensions exhibited rheological behavior akin to what has been reportedly observed for some solid‐rocket motor propellant compositions. NMR‐derived flow velocities of these suspensions at high particle loadings show clear deviations from the Newtonian parabolic behavior and some unusual intensity features which are not yet fully understood. The capabilities and limitations of NMR flow imaging as well as considerations for data interpretation in the special case of highly filled suspensions is discussed.