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Measurement of granular temperature and stresses in risers



Detailed experimental velocity, particle concentration, and stresses for flow of particles in a vertical pipe, riser are needed for verification of various CFD models for multiphase flow. This is the principle-unsolved task of the Fluid Dynamics Multiphase Flow Consortium, organized by Dow Chemical Company. This study provides such information for flow of 530 μm glass beads in the fully developed flow region of a 7 m symmetric riser with a splash plate. Instantaneous particle-velocity distributions were obtained using a particle velocity imaging technique, and a probe inserted into the riser, while the particle concentrations were measured with a gamma-ray densitometer. Time-averaged particle-velocity distributions can be well represented by a parabolic- velocity distribution, with the mean velocity obtained from flux divided by the measured bulk density. The flow is very anisotropic. The radial granular-temperature profiles agree with an analytical expression similar to the thermal-temperature distribution in Poiseuille flow with viscous heat generation. A numerical solution for the standard isotropic model developed shows that the approximations made in the analytical solutions are reasonable. In the core, the normal Reynolds stresses are much smaller than the velocity averaged particle stresses, whereas near the wall the time averaged normal Reynolds stresses are large. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1760–1775, 2004