Velocity and concentration studies of flowing suspensions by nuclear magnetic resonance imaging. Technical progress report, quarter ending December 31, 1995

Task 1: PARTICLE SELECTION. Poly(dimethylsiloxane) was examined as a possible liquid to use with pills for studying granular flows. It however has a weak silicon-29 signal, and it will be difficult to measure a flowing sample. Among the other contrast mechanisms that will be pursued is the spin-lattice relaxation time T{sub 1}. Task 5: FLOWS IN COMPLEX GEOMETRIES. NMR imaging was used to measure the concentration and velocity profiles flowing through a straight pipe into and out of 4:1 contraction and expansion. Complex spatial variations could be induced in particle concentration in this way, and it may be difficult to maintain a well-mixed suspension while filling a vessel from an inlet tube with a cross section smaller than the vessel. Demixing effects are much larger in suspensions of coarse particles than in suspensions of finer particles