NUMERICAL-ANALYSIS OF LIQUID-SOLIDS SUSPENSION VELOCITIES AND CONCENTRATIONS OBTAINED BY NMR IMAGING

Analyses of some of the steady-state, fully developed, and isothermal carrier fluid velocity and solids concentration data of Altobelli et al. [1] and Sinton and Chow [2] obtained using three-dimensional time-of-flight nuclear magnetic (NMR) imaging techniques are presented in this paper. NMR imaging offers powerful techniques to nonintrusively determine three-dimensional time-dependent velocity and concentration fields to assist development and validation of the constitutive models and the computer programs describing concentrated suspensions. These experiments were carefully performed and probably represent the best available open literature data of their kind. COMMIX-M, a three-dimensional transient and steady-state computer program written in Cartesian and cylindrical coordinates, has been used to analyze the NMR data. This computer program is capable of analyzing multiphase flow and heat transfer and utilizes the separate phases model wherein each phase has its own mass, momentum, and energy equations. COMMIX-M contains constitutive relationships for interfacial drag, solids viscosities and stresses to describe the solids theology, and virtual mass and shear lift forces extended to a continuum from the single particle literature. Also included is a solids partial-slip boundary condition to allow nonzero tangential velocity at the tube walls. This computer program is being developed at Argonne National Laboratory for application to test various interphase interaction models and to predict design and processing of dense fluid-solids suspension systems. Comparisons of computed and measured concentration and velocity profiles provide some insights into the mechanisms governing the observed phenomena. Recommendations for model improvement are given. To the authors'knowledge, these are the first such comparisons of theory and experiment.